A Performative Approach To 3D Printed Architecture // Luca Breseghello by Luca Breseghello

A PERFORMATIVE APPROACH TO 3D PRINTED ARCHITECTURE BACHELOR THESIS

LUCA BRESEGHELLO, 777034

Politecnico di Milano, Facoltà di Architettura e Società Bachelor in Science of Architecture Supervisor: Prof. Ingrid Paoletti Co-supervisor: Roberto Naboni Academic year: 2013/2014

Ai miei nonni.

ABSTRACT Additive Manufacturing is considered a revolutionary manufacturing technique, changing the concept of what we can produce and the modality of production. Architects and construction companies look with interest to the 3D printing phenomenon as a game-changer in the creation of novel architectural forms and as an innovative construction process to be explored. While an international community comprised of architects have tackled many experiments in the recent years, one main question is substantially not answered yet: how do we build with 3d printing? The thesis, organized in two parts, attempts at answering this question either referring to the existing experiments across the world, either developing an experimental design of a 3d printed construction system. The first part, entitled “State of the Art in Additive Manufacturing in Architecture”, analyses 3d printing for direct building applications. Additive Manufacturing techniques are analyzed towards their potential application referring to their main material constituents which determines different deposition techniques, offering a wide range of solutions in process and results. A study on the existing applications in architecture highlights the potential of direct implementation of 3d printed components across different scales and systems: from punctual connection elements (joints) to megalithic constructions (direct printing of residential units). Two fundamental considerations emerge from the outlined literature review. Firstly, the material engineering of specific materials for constructions is an actual need in determining the influence of AM in the future construction site. Secondly, considered the contemporary techniques and material development, the exploration of assembly systems made of printed components appears to be the most promising area, where the benefits of precision, customization and material development find their best intersection. The second part “Design Experiment in 3D Printing” is focusing in proposing an experimental process for the development of a construction system for building skins. In developing specific design and construction mechanism for additive manufacturing, the most advanced design techniques are involved to control heterogeneous material organizations, within a performancedriven perspective. The developed design case study is ambitiously trying to extend state-ofart design techniques in the realization of a temporary pavillion. The tabula rasa design involves the creation of an entire parametric workflow, to generate a structural skin which optimizes its mechanical behaviours. A multi-scalar design optimization is proposed to obtain a topologically optimized structural layout later refined with custom-developed structural patterns.

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CHAPTER 01 // INTRODUCTION

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1.1 Additive Manufacturing Potentials 1.2 The Km 0 Factory 1.3 Non-Standard Manufacturing 1.4 About This Thesis References PART I // STATE OF THE ART IN ADDITIVE MANUFACTURING IN ARCHITECTURE CHAPTER 02 // THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING 2.1 A Material-driven categorization 2.2 Semi-solid material extrusion 2.2.1 Plastic extrusion 2.2.2 Semi-liquids extrusion 2.2.3 Metal extrusion (FDMm) 2.3 Granular materials binding 2.3.1 Binder jetting 2.3.2 Selective Laser Sintering (SLS) 2.3.3 Selective Inhibition Sintering (SIS) 2.4 Liquids photopolymerization 2.4.1 Stereolithography (SLA) 2.4.2 Digital Light Processing (DLP) 2.4.3 Multi jet modelling (PolyJet) 2.5 Printing-Material Engineering 2.6 There Is Not (Yet) a 3D Printer for Architects References

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CHAPTER 03 // CASE STUDIES OF 3D PRINTING IN ARCHITECTURE

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3.1 Classification Methodology 3.2 Printed Joints 3.2.1 3D Printed Steel Joints - Arup 3.2.2 3D Printed Nodes Shrouds - Fletcher Priest Architects 3.3 Construction Components 3.3.1 Customized Ceramic Bricks: Building Bytes & PolyBricks 3.3.2 Quake Column - Rael, San Fratello 3.3.3 Plastic Pavilions: Echoviren & ProjectEGG 3.3.4 3D Print Canal House - DUS Architects 3.4 Monolithic Structures 3.4.1 Digital Grotesque - Hansmeyer, Dillenburger 3.4.2 Villa Roccia Project - James Gardiner, D-Shape 3.4.3 Contour Crafting - Behrokh Khoshnevis 3.4.4 Concrete Printing - Loughborough University 3.4.5 3D Printed Homes - WinSun Design Engineering Co. 3.5 Moldings 3.5.1 Concrete casting - Philippe Morel 3.5.2 Mesh-Mould - Gramazio Kohler Research, ETH 3.6 The different dimensions of 3D Printing in Architecture References

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CHAPTER 04 // MATERIAL [MORPHO]LOGICS 4.1 Material implications in architectural design 4.2 Macro-scale material organization: Topology Optimization

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4.3Micro-scale material organization 4.3.1 Heterogeneity 4.3.2 Anisotropy 4.4 Variations in Geometry 4.5 Variations in Material Intrinstic Properties References

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PART II - DESIGN EXPERIMENT CHAPTER.05 // DESIGN AND FABRICATION STATEMENT 5.1 Design Assumption 5.1.1 Direct Digital Manufacturing 5.1.2 Architectural application: Building Skin 5.1.3 Architectural Printing Scale: The Component 5.2 Fabrication Context 5.2.1 3D Hubs Service 5.2.2 PiÃ¹ Lab Workshop 5.2.3 Makerbot Z18 5.2.4 Visiting the Italian 3D Printer Producers References CHAPTER.06 // PROJECT DEVELOPMENT

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6.1 Goals 6.2 Assumptions

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6.3 Operative framework 6.3.1 Material system 6.3.2 Fabrication and Software Framework 6.4 Top-down shape definition 6.5 Topology analysis 6.5.1 Shell topology analysis variables 6.5.2 Interpretation of the topological analysis 6.6 Performative tasselation 6.7 Multi-scalar organization of the structural pattern 6.7.1 Thickness optimization 6.7.2 Micro-structural organization 6.8 Final results and future developments

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BIBLIOGRAPHY

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LIST OF FIGURES

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INTRODUCTION

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INTRODUCTION

1.1 ADDITIVE MANUFACTURING POTENTIALS Modern additive manufacturing (AM) technology traces back to the mid 1980s with the advent of stereolithography, commonly known as 3D printing. Over the subsequent years, the research community has found ways to apply these processes and process variations in novel ways to solve a wide variety of research problems in a diverse number of technical areas. Nowadays, due to the wide range of its advantages, the impact of additive manufacturing continues to grow in terms of both commercial and scholarly activities, constantly setting new issues to be resolved and conquering new areas of application (Lipson, 2013). More specifically, additive manufacturing is defined by a set of technologies that are translating virtual model data into physical objects in a rapid and simple way. The data is broken down into a series of 2D cross-sections of a finite thickness. These cross-sections are fed into AM machines so that they can be

combined, adding them together in a layer-bylayer sequence fabricating the final geometry (Gibson et al., 2014). One of the main benefits of AM thus, becomes the â&#x20AC;&#x153;rapidâ&#x20AC;? nature of the process itself, related to the speeding up of the overall manufacturing, usually performed in a single step and almost entirely with the use of computers. This drastically bridges the gap between design and fabrication, reducing the number of the project stages through the implementation of a direct design-build system. AM gives freedom to innovate, moving away from the notion of design as a static procedure and enabling architects and engineers to test multiple iterations simultaneously with minimal additional costs (Gibson et al., 2014). Furthermore, the process enables the fabrication of complex structures, ranging from the overall geometry or a part of it to the topology of its internal organization to the spatial distribution of its material composition.

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Along with the freedom of fabrication though, increases also the design challenge to include representation and optimization of intricate geometries and functionally graded structures. Unlike other fabrication processes like milling, cutting, etc, additive manufacturing results in almost no waste of raw materials due to the nature of the process itself - starting with an empty building plate and adding only the necessary material. The fabrication can be additionally optimized in order to reduce the amount of material needed by implementing

internal air gaps or open lattice structures into the design. The compressed manufacturing process combined with these characteristics equate to a significantly smaller environmental footprint. Layer-based manufacturing allows us to integrate structural and environmental optimization directly into the design stage, creating a seamless process that results into a significant decreasing in time and use of resources (Duro-Royo et al., 2014).

INTRODUCTION

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INTRODUCTION

1.2 THE KM 0 FACTORY Additive manufacturing is not changing only the way we produce things but is also affecting logistics, supply chain and shipping. Currently our production system requires the transportation of goods and materials from and to every part of the world which involves the vast use of natural resources. This system is becoming highly unacceptable in the conditions of growing resources scarcity and environmental crisis (Bollinger et al., 2010). Gone are the days of mega, or even giga-factories that consume tremendous amounts of time and energy to fabricate products. A more sustainable and flexible factory is on the horizon. Called microfactories, these diminutive factories drastically change how we produce large consumer goods for unique local needs (Local Motors, 2015). The recent advancements in the field of digital design and fabrication give us the opportunity to eliminate the transportation-related costs by implementing a streamline manufacturing process instead of the traditional centralized model. The technologies that underlie AM enable the rapid,

flexible, and cost-efficient design and production across many applications and industries around the world. Layer-based manufacturing makes it possible to transform digital models into concrete physical objects almost simultaneously and at the same location or at any other location in the world - â&#x20AC;&#x153;justin-time, on-demand manufacturingâ&#x20AC;? (Lipson, 2013). On the other hand, the growth of the AM industry leads to the development of innovative product ideas and component designs, new processes and technologies, novel materials and specialized softwares. Local communities and interested individuals have the opportunity to contribute directly to these processes. This can consequently help creating new jobs and boost local economies, generating a distributed, sustainable employment system. This requires significantly lower energy consumption compared to the conventional centralized manufacturing and product distribution models, which as I already mentioned often requires long-distance transportation of goods and materials (Gibson et al., 2014).

figure 1.1 Traditional supply chain vs. 3D printing supply chain

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A TRADITIONAL SUPPLY CHAIN Manufactured goods are “pushed out” and distributed through warehouse networks to customers

Long lead time

High transport costs

Products are mass produced (e.g. in China)

Large carbon footprint

INTRODUCTION

A 3D PRINTING SUPPLY CHAIN

Locally printed and distributed

Short lead time

Customized production. “Puled” by end customer demand

Low transport costs

Low carbon footprint

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INTRODUCTION

1.3 NON-STANDARD MANUFACTURING Additive manufacturing technology is stillnascent and maturing but it continues to evolve rapidly both in response to and as a main driving force behind a new industrial paradigm, referred to by many as a New Industrial Revolution. It is characterized as a shift from mass production to massive customization at the blurring boundaries between bits and atoms, between digital and material, between designing and producing. The First Industrial Revolution brought mechanization, centralized factories and industrial capitalists. The Second Industrial Revolution brought the automation, the conveyor-belt and the social division between white and blue collar work. These two phenomena rejected the customization and the multi-functional and multi-performative design. This industrial logic ensured constant and repeatable quality, but at the same time limited innovation, differentiation and the range

of what was buildable. The implementation of a superior universal module that is setting the standard geometry, tolerance and construction process is an inseparable part of this logic. Any deviation from this ideal model is increasing dramatically the cost and the production time that is required. In the realm of architecture, industrialization created a sharp distinction between the roles of the designer and the engineer, the architect and the final user (Troxler, 2013). The New Industrial Revolution, on the other hand, implies a transformation of architecture from a top-down irreversible production chain into a democratic, flexible and bottom-up ecosystem. For the first time, architects have the opportunity to incorporate the two seemingly distinct worlds of digitality and materiality in order to create an emerging reality, synthesis of data, material, programming, computation and fabrication. Through the use of novel tools

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and methods for design and manufacturing, architects can keep the control over the data flow and the intricate interaction between hardware and software (Naboni and Paoletti, 2015). Furthermore, with the advances of additive manufacturing in the last decade, we have the possibility to reconsider masscustomization, where an item can be produced according to the specific needs of the design but in an efficient way and without losing its initial functionality. Layer manufacturing also implements a continuous digital workflow that similarly to the traditional industrial logic comprises a coordination module but in this case it is adapted to the novel technological scenario. The superior element in such a process is the generative algorithm which produces data subsequently transformed into a numeric control programming language (G-code). Form is differentiated from the fundamental principles organizing the different

elements within the manufactured component. None of the components is considered as an ideal primary model; every element might differ in geometry and form as long as the intricate logical interrelations are accurate. The bigger the variation and the complexity, the higher is the value and the benefit of using an AM machine (Bollinger et al., 2010). This consideration leads to an important aspect of the changing notions of architecture: the shift from geometry conceived as an external regulator of materials to a notion that recognizes the inherent performances and behaviours of matter. The blurring boundaries between form, matter and function are pushing the architect away from the essentialist concept that matter is formless and geometry should be imposed over it regarding its own capacities for self-organization and morphogenesis. The role of the architect in this novel field is also changing:

â&#x20AC;&#x153;...neither a passive observer of determined systems nor a determined manipulator of passive material, but rather, the manager of an unfolding process.â&#x20AC;? (Reiser and Umemoto, 2006).

figure 1.2 Some statistics on additive manufacturing (3D printing)

INTRODUCTION

Additive manufacturing and material practices offer architects the opportunity to question some of the restrictive assumptions that are deeply embedded in modernist design thinking and reinforced by the traditional industrial chain logics. Thanks to the advances in these fields, we can apply strategies for form-generation bringing maximum performance with minimal

resources through local material property variation and optimization. This approach might result into a more integrated construction system avoiding the strict separation between different building components that are typically mass-produced and not adaptable and customizable according to the need of the architecture (Oxman, 2010). € 7.7 bln € 4.5 bln

€ 2.2 bln

€ 0.9 bln 2008

2013

2018

2023

PROJECTED SIZE OF THE GLOBAL ADDITIVE MANUFACTURING MARKET 38%

$ 668 mln USA

ers Oth

$ 412 mln

2013

h in

34.2%

$ 288 mln

9. 7

Jap

G er m a

8.7

9.4%

2012

DISTRIBUTION OF 3D PRINTING MACHINES IN 2013, BY COUNTRIES

2013

2014

WORLDWIDE END-USER SPENDING ON 3D PRINTERS

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INTRODUCTION

1.4 ABOUT THIS THESIS This research explores the emerging challenges and opportunities of additive manufacturing application for architecture, ranging from new developments of processes and materials to new simulation and design tools, as well as informative applications and case studies. The first part of the thesis is comprised of three chapters and outlines the various types and applications of additive manufacturing in the realm of architecture, design and construction. In particular, Chapter 2 gives an overview of additive manufacturing (AM) techniques, looking at the different printing technologies as well as at the materials used for the fabrication. The processes described in the chapter, have been subdivided according to the initial state of the material used. The first group of techniques is characterized by the process of extruding a material referred to as semisolid material extrusion and it includes plastic

extrusion, semi-liquids extrusion (e.g.clay, concrete, etc) and metal extrusion. The second group refers to the process of selectively binding together the granules of successive layers of fine powders that might be made of different materials like plastics, metals or ceramics. The third one describes the process of liquid photopolymerization that uses liquid, radiation curable resins, or photopolymers as their primary materials. Upon irradiation, these materials undergo a chemical reaction to become solid. At the end of the chapter a synopsis of the materials that are commonly used is provided highlighting the emergence of innovative ones developed specifically to answer the needs of different AM processes. Chapter 3 investigates a selection of relevant case studies on additive manufacturing applied in the architectural and building construction context. According to the different approaches implemented in the projects, a classification of

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four main groups emerged: joints, components, monoliths and molds. A common analytical framework has been used describing the production techniques, the materials, the scale of the building and the function of the 3D-printed elements within it. That framework allows a better understanding of the potentials and the weaknesses of every approach. Chapter 4 recognizes the emergence of new paradigm in architecture based on the opportunities offered by computational design and digital fabrication. These novel techniques not only make possible the generation of complex shapes but also allow us to organize the internal material distribution over the volume, according to desired parameters. Through the chapter, different optimization approaches, implying mutations at varying scales have been identified: those which involve a modification in the external shape of the analysed object or system, and those which entail an heterogeneity or anisotropy across the

volume, under the form of geometrical variation or material properties mutation. The second part of the thesis includes two chapters which represents my practical experience in additive manufacturing, culminating in the project for a temporary pavillion. Chapter 5 includes the practical experiences I had the opportunity to gain through various workshops and my direct collaboration with producers and practitioners in the field of additive manufacturing. Based on this experience and on the extensive research defining the state of the art of the technology, I define the technological premises and my personal approach towards the use of 3D printing in architecture. The last chapter describes the goals and the operative framework of my proposal, the design process including form-finding and topological optimization approach, the trials and at last the final results.

INTRODUCTION

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INTRODUCTION

REFERENCES Bollinger K., Grohmann M., Tressmann O. (2010) Structured Becoming: Evolutionary

Processes in Design Engineering. In: Oxman R., Oxman R. (2010) The New Structuralism. AD, vol.80, No. 40. John Wiley & Sons, London. Duro-Royo J., Zolotovsky K., Mogas-Soldevila L., Varshney S., Oxman N., Boyce M., Ortiz C.(2014) MetaMesh: A Hierarchical Computational Model for Design and Fabrication of Biomimetic Armor Surfaces. ComputerAided Design, Elsevier , Vol. 60, pp. 14â&#x20AC;&#x201C;27. Gibson I., Rosen D., Stucker B. (2014) Additive Manufacturing Technologies. Springer, NYC. Lipson H., Kurman M. (2013) Fabricated: The New World of 3D Printing. John Wiley & Sons Ltd., Chichester. Local Motors (2015) 3D Printed Car. www.localmotors.com/3d-printed-car. Accessed 12 February 2015. Naboni R, Paoletti I. (2015) Advanced customization in architectural design and construction. SpringerBriefs in Applied Sciences and Technology, Springer, Dordrecht. Oxman, N. (2010) Material-based Design Computation. Ph.D. thesis, MIT. Reiser J., Umemoto N. (2006) Atlas of novel tectonics. Princeton Architectural Press, New York. Troxler P. (2013) Making the 3rd industrial revolution. In: Walter-Herrmann J, BĂźching C (ed) FabLabs: Of machines, makers and inventors, Transcript Publishers, Bielefeld.

STATE OF THE ART IN ADDITIVE MANUFACTURING IN ARCHITECTURE

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

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THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.1 A MATERIAL-STATE-DRIVEN CATEGORIZATION This chapter will give an overview of additive manufacturing techniques, looking at the different printing technologies as well as at the materials used in the fabrication. Additive processes are often named as ‘Rapid Manufacturing’, where the term ‘rapid’ is not about the time it takes to build parts, but more on the speeding up of the whole product development process, which relies much on the fact that computers are used throughout, and that building realized with an AM machine is generally achieved in one single step, cutting off all those stages of the project where for a simple change in the design a significant increase in time (and costs) may result (Gibson et al., 2014). Additive manufacturing technology thus drastically reduce the gap between project and production phase, creating a direct design-build system. This explicit connection between designer and manufacturer,

which may easily be the same person for simple production cases, requires the first to have a clear knowledge of fabrication techniques, in order to be able to collaborate directly in the printing phase but also to be able to implement and tune the design to capitalize on the production process in use. Compared to other manufacturing techniques, AM involves a reduced number of steps that transform a virtual CAD description into tangible objects. The first step is the design of a 3-dimensional model of the object and its conversion into a triangulated mesh. The model is then usually exported in stl. (stereolithographic) format. The second step comprise the use of an external software that is analysing and virtually “slicing” the meshed model into layers according to predefined settings. A path is then generated and translated into a G-Code file which contains all the

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instructions for the printer. In the last, third step, the G-Code is transferred to the printer through a USB, SD, etc. The machine follows strictly the instructions, moving the extruder in the desired path, building layer-by-layer the final object. A large number of printing techniques has been studied and tested through years, but a sort of natural selection took place, since just some of them had a good success which brought them to be commonly used and further implemented, adapted and developed. Others have gone lost for different reasons, ranging from expensive costs to excessive imprecisions. Different criteria of classification of Additive Manufacturing processes has been taken into account in literature. In particular Karunakaran

DIGITAL MODEL

exposes different possible options (Karunakaran et al., 2012). A first option is to take as the driving aspect the type of material printed by the machines, which can turn out to be problematic because some machine can print more than one material typology. A second option refers to the material matrix, thus the ability of printers to work with a monolithic, composite, or gradient matrix, in terms of materic composition and properties, but it may result too specific with respect to the scope of the research. Another possible classification is according the final application of printed objects, which ranges from the visualization model to the high-end engineering part; again here, some printers may be used for different purposes, and moreover this

SLICING SOFTWARE

FABRICATION

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

subdivision would not clarify the different classes of layer manufacturing technologies and their behaviors. Always according to Karunakaran, more subdivision options can be referring to number of materials involved, on the energy source (laser, EB or arc) used, on the boolean nature of the manufacture (laminated, powder-bed or deposition) or differencing methods of joining particles, but these approaches are too generic or too specific, not allowing a proper classification of the processes. The approach used by Gibson, is to manage the additive manufacturing techniques according to the starting condition of the material before it is worked by the machines (Gibson et al., 2014). He defines liquid polymers, discrete particle, molten material and solid sheet systems. Often

FDM

machines can print different classes of materials, and for different final purposes, but each printer can handle just materials in specific initial states, therefore this criteria is defining a proper subdivision which highlights the characteristics of the material processing, defining advantages and disadvantages of every process category. The following analysis aims at understanding the intrinsic advantages and disadvantages of every layer manufacturing process, but also the positive and negative aspects of each of them with respect to a possible application in the architectural field. It will thus clarify if there is a ready appropriate technology for architectural use, which are the eventual weak points and needed implementations.

GRANULAR

LASER

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THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.2 SEMI-SOLID MATERIAL EXTRUSION The first group of layer manufacturing techniques is characterized by the process of extrusion of material. Machines can be of two main topologies: gantry or delta. The first group of printers is characterized by a gantry system, where usually is moving the material extruder, in the X and Y dimensions, meanwhile the plate where the material lays down is moving in Z direction. They thus use the Cartesian system to control movimentation. This is the easy way of getting from point a to point b because a straight line is just one plane or one axis moving. The downside is that the moving parts are quite heavy. A 3D printer needs to be able to change it’s direction instantly and as fast as possible. The heavier the moving part, the harder it is to make it stop or

change direction in an instant. For this reasons, a different approach has been developed, based on the “delta system” of parallel robots. It consists of three arms connected to universal joints at the base. The key design feature is the use of parallelograms in the arms, which maintains the orientation of the end effector. The benefit of a delta is that the moving parts are lightweight so that it’s easier to travel. That results in faster printing with greater accuracy. Different materials can be extruded with just small changes in the technology: plastics are the most diffused and easily printable material used, but in last five years experimental projects brought ceramics, clay, and even cement to be extruded with an additive fabrication machine.

2.2.1 PLASTIC EXTRUSION Today a large portion of the 3D printers create objects by extruding a semi-liquid material

from a computer-controlled print head nozzle. Although this process can be used to 3D print

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

objects in a wide range of materials, including metals, concrete, ceramics and even chocolate, by far the most common material that is extruded is a melted thermoplastic. Being the 3D printing industry under continuous development, there is not a defined vocabulary and it happens that different terms, related to machines parts or processes, mean exactly the same thing. The fact that many labels are patented does not help to share a common univoque terminology. It is the case also with “thermoplastic extrusion”, also generically described by the label “material extrusion”, as stated in 2012 by the global standards body ASTM International (Barnatt, 2013) . Things are complicated by the fact that the marketleading company Stratasys labelled it “Fused Deposition Modelling” (FDM), making it a widely used and misused term for material extrusion in general. Other commonly used definitions are “Fused Filament Modelling” (FFM) and “Fused Filament Fabrication” (FFF). Along this thesis I will describe the aforementioned process as “thermoplastic extrusion”, which properly focuses on material and process in use.

The process of thermoplastic extrusion needs a spool of material, referred to as “filament’” which is slowly fed to a print-head that is heated to between 200 and 300°C. This temperature melts the filament, which is then extruded through a fine nozzle and flattened slightly by the print head on its way out. The first layer of molten filament is deposited directly onto a horizontal, flat and smooth surface known as “build platform”. Here the filament very rapidly cools and stick, very often helped by one or two fans attached to the print head, which is moving in 2D space to trace out the first layer of the object being printed. Once the first layer of the object has been traced out, the build platform lowers very slightly and the next layer of thermoplastic is deposited on top of it. This process repeats until a complete plastic object has been printed. Many materials can be used as thermoplastic filament, where the most common are acrylonitrile butadiene styrene, known as ABS, and polylactic acid, PLA. ABS is a petroleum-based non-biodegradable plastic, widely adopted in industrial injection

figure 2.1 Filament Sculptures designed by generative artist Lia who has been exploring the possibilities of thermoplastic extrusion by defining the location of the printhead, the speed of the movement and the amount of filament that should be extruded

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molding processes and it is very significant that thermoplastic printing can produce items with the same material, hence material properties, as standard injection molded parts. This allows manufacturers to rely on known performances for strength, durability, safety and other aspects of the plastic. On the other side PLA is a bioplastic currently made from agricultural products such as corn starch or sugar cane, being far more environmental friendly than ABS. ABS printing temperature ranges from 230 to 250Â°C, whereas PLA is easier to be printed being correct printing temperature around 200-215Â°C. The higher temperature together with intrinsic characteristics of the material makes ABS having a much higher shrinkage factor than PLA, creating adhesion problems and distortions. To avoid this problems a heated build platform has been implemented on many machines, allowing a more gradual cooling of the plastic. Different variants of these two has been studied and tested, for better performances or different aesthetics appeal, such as ABS-polycarbonate, or the Laywood

PLA, with a percentage of wood fibres which gives a wooden look to the plastic. Many other plastic materials have been developed and commonly used, such as Nylon, PET, HIPS and also flexible ones such as TPU. Most of the plastics can produce filaments in a variety of solid and translucent colors, and at the time of writing prices range between 20-50 â&#x201A;Ź/Kg, but they are going to drastically decrease thanks to the great expansion of the market (Barnatt, 2013). Common desktop 3D printer has a build volume which range around 10 to 30 centimeters per every axis, but some bigger machines are already on the market and huge custom machines which aims at printing in the order of a meter have been developed for specific projects. It is possible to buy a cheap and tiny 100$ Peachy Printer in a kit to be assembled while one most expensive industrial machine, the Stratasys Fortus 900 can be purchased with not less than $400,000 (Wikinvest, 2014). An important design consideration when using FDM is to account for the anisotropic

figure 2.2 The Replicator 2 - a market-leading desktop 3D printer from Makerbot Industries (MBI)

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

nature of a part’s properties. Moreover, different layering strategies result in different strengths. Usually, properties are isotropic in the x–y plane, but if the raster fill pattern is set to preferentially deposit along a particular direction, then the properties in the x–y plane will also be anisotropic. In almost every case, the strength in the z-direction is measurably less than the strength in the x–y plane. Thus, for parts which undergo stress in a particular direction it is best to build the part such that the major stress axes are aligned with the x–y plane rather than in the z-direction. Thermoplastic extrusion has some limitations, which may be a problem or not depending on the application field. The first, and maybe the most evident, is the support of overhanging parts: when the extruded plastic has nothing to adhere on, it is going to fall down. Generally 45° degrees is considered the limit for a stable object construction. Over that limit some additional supports have to be conceived, printed and then removed. Some machines

has two extrusion heads, giving the possibility to use one to extrude a dissolvable material for supports, which is easier to be removed and gives a better quality of the final object. Another limit of thermoplastic extrusion is the so-called “stepping”, visible and sensible effect of the layering process, which will create a stepped surface, as opposed to an injection moulded object which has as smooth surface. The stepping can be considered a minor problem at the construction scale, being a problem in the order of millimeters, depending on the resolution of the printer. Last but not least, in particular printing big object, the speed of the process can be a problematic issue: in fact to print a full cube 20x20x20 cm it might take more than 24 hours, always depending on the layer thickness, which drastically influences the printing time.Possible solution already taken in consideration, in particular at a bigger scale, such as construction, is to use a bigger printing nozzle and higher layer thickness, having less precision but way faster printings.

figure 2.3 A model printed with a do-it-yourself color blending extruder using a single hot-end with multiple driven feeds

2.2.2 SEMI-LIQUIDS EXTRUSION Material extrusion 3D printing is not just about thermoplastics. Different materials with a slightly similar fabrication process are currently used, starting from clay. It is not a consolidated technique, but many projects from artists and researchers have developed and used machines to extrude clay similarly to thermoplastic extrusion processes. The printers usually works in the same way, having a build platform and a print head which moves creating layer upon layer the desired object.

The main difference lies in the process of extrusion of the material: every project is slightly different, but usually a clay and water mixture is pushed into the print head by a pressure, without any need of heating and fusion. Commonly, the smaller clay printers use a syringe controlled by a stepper motor, while the bigger use a time-pressure valve system, an air pump coordinated with the movement of the printer. Printed pieces can vary from 10 cm to even 1 m height. Particularly interesting for construction industry, in a similar fashion many researches

figure 2.4 A design from the 3D Woven collection of functional 3D printed ceramics by Olivier van Herpt which features a weave pattern reminiscent of artisan-made work

have been working about extrusion of concrete for possible applications in building technology. Given that concrete is initially mixed into a viscous form that is poured before it sets, it is quite immediate the possibility of pushing it through a motion-controlled nozzle in its naturally pre-set state to form layers that then solidify. Printing time but moreover limited extrusion precision and freedom are the major limits of the technology at the moment, not yet producing acceptable results ready for the market, but opening perspectives for a revolution in the construction field.

One of the benefits of 3D concrete printing could be the fabrication of complex curves and designs that are hard if not impossible and expensive to be manufactured with traditional building techniques. Moreover while at present all walls and floors cast in concrete have to be solid, 3D printing will therefore be able to be crafted with internal air pockets to improve insulation and to reduce materials usage. Drastically reduced costs and projectproduction time, together with more safety on construction site are additional relevant potentials of concrete additive manufacturing.

figure 2.5 Ceramic 3d printing project developed by Unfold in 2009 features a custom software that allows detailed line level control, unlocking a new form language in 3d printing

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2.2.3 METAL EXTRUSION (FDMm) A currently experimental and promising new variant of the technology is the “fused deposition modeling of metals”. This generation of machines usually derives from a modification of standard thermoplastics printers to allow them to extrude metal alloys. The alloys used has to have a relatively low melting point (of less than 300 °C), but, given this constraints, metals have been successfully heated and extruded to form objects in layers that were just under a millimetre thick. A proper example is the research developed by the team led by Jorge Mireles at the University of Texas. With an alternative approach, other researchers have successfully adapted gas

metal arc fusion welding robots to achieve the fused deposition modelling of metals. For example, researchers at Cranfield University have worked in partnership with Lockheed Martin to study a sort of FDMm that they call “wire and arc additive manufacturing” (WAAM). The 3D printing hardware they have created is similar to a computer-controlled arc welder that also happens to extrude molten metal. A thin wire of titanium is threaded through a movable arm, melting the tip of the wire concurrently. The technology is a lot slower than traditional manufacturing, but very little waste of the expensive material is wasted.

figure 2.6 A 17 year old developed a prototype for the first desktop based metal 3D printer and launched a Kickstarter campaign to fund the production

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THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.3 GRANULAR MATERIALS BINDING The following set include all those techniques which use materials in a powdery state. This refers to a wide range of processes that 3D print objects by selectively sticking together the granules of successive layers of a very fine powder. Such powders can be made of different materials, from plastics to metals, but also ceramics, and may generally be formed

into solid in two distinct ways. The first category of machines uses a print head to spray a “binder” onto the build material, whereas the second group of technologies take advantage of laser or other heating technology to partially (sintering) or completely fuse the granules of powder together.

2.3.1 BINDER JETTING Additive manufacturing machines which uses an inkjet-style print head to spray a glue or a “binder” onto successive layers of powder are often the only hardware that experts refer to as “3D printers”. Unfortunately, this makes things confusing for most of the people, that are referring to “additive manufacturing” as “3D printing”. That’s why in 2012 has been decreed that this kind of technology ought to be named “binder jetting”.

The build process starts when a layer of powder is laid on a build platform, often termed as “powder bed”. This is usually achieved by raising the base of an adjacent powder tank and using a sweeper blade or a roller to push the powder so across the bed. A multi-nozzle inkjet print head then moves across the powder bed, selectively jetting a binder solution, shaping the first layer of the object. The powder bed is then lowered, another layer of powder is laid

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

down, another layer of binder is jetted onto it, and so on until the object is completed. When the printing process finishes the completed part has to be left to cure (for around an hour) in the remaining, dry, powder within which it remains encased. When curing is finished, some of the latest binder jetting machines automatically remove most of the loose powder from around an object using a vacuum system. This allows to clean-up the object but also to recycle the unused powder for later use. The object is then moved from the powder bed to a “depowdering chamber” in which it is sprayed with compressed air until it is completely clean. This chambers are built-in in the latest printers in a negative-pressure vacuum system that allows again to recycle the remaining unused powder so that no material is wasted. In the original implementations, starch and gypsum plaster fill the powder bed, the liquid “binder” being mostly water to activate

the plaster. The binder also includes dyes (for color printing), and additives to adjust viscosity, surface tension, and boiling point to match print head specifications. The resulting plaster parts typically lack “green strength” and require infiltration by melted wax, cyanoacrylate glue, epoxy, etc. before regular handling. As a general rule parts fabricated using binder printing processes tend to have poorer accuracies and surface finishes than parts made with direct printing. Infiltration steps are needed to fabricate dense parts or to ensure good mechanical properties (Gibson et al., 2014). 3D printing technology has a limited potential to vary material properties in a single build, but is generally limited by the use of a common core material. In the original Z Corporation systems, cross-sections are typically printed with solid outlines (forming a solid shell) and a lowerdensity interior pattern to speed printing and ensure dimensional stability as the part cures.

figure 2.7 One of the major producers in the field of layer-based manufacturing, voxeljet, has developed a new method for 3D printing which uses phenolic resin binders (Phenolic-Direct-Binding). The picture shows their printing process with temperature management

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.3.2 SELECTIVE LASER SINTERING (SLS) The use of a binder is just one among different options to stick particles together. The second set of techniques take advantage of heat, selectively applying it to bond adjacent powder granules in a process generically called â&#x20AC;&#x153;powder bed fusionâ&#x20AC;?. The first adopted and most widespread powder bed fusion technique is selective laser sintering (SLS), where particles of plastic, ceramic or glass are fused and thus bond together by heat from a high-power laser to form the solid three-dimensional object. It was developed and patented (Deekard, 1989) in the 1980s by Carl Deckard, then an undergraduate student at the University of Texas, and Joe Beaman, his mechanical engineering professor. Similarly to binder jetting, the process begins with a layer of powder rolled across a powder bed. Then, differently from the previous technique, a laser beam traces out the crosssection of the first layer of the final object. The laser heats the powder either to just below its boiling point (sintering) or above it (melting),

fusing granules of the powder together. Once the initial layer is formed, the platform of the SLS machine releases a new bed of powder for the laser to trace and fuse together. The process continues until the entire object has been printed. Then the item is left to cool in the machine before being removed. Differently from other additive methods, SLS requires little additional tooling, such as sanding or other alterations, once the object is ready. Moreover, SLS, similarly to binder jetting, does not require any additional temporary support to hold an object during the printing process. To make the operation of melting easier, the SLS printer build chamber is pre-heated to a temperature just below the melting point of its build material. One of the reasons why this process is quite expensive is that to create objects in materials other than composites, plastics and waxes, expensive lasers that can raise materials to very high temperatures are required.

figure 2.8 American firm 3D Systems has used 3D scanning technology and selective laser sintering combined with robotics in order to create the first exoskeleton to help paralysed patients

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SLS can build objects using a wide variety of powdered materials. These include plastics, such as nylon, sand, ceramics, wax and even metals. Itâ&#x20AC;&#x2122;s also possible to adopt a twocomponent powder material, where a powder with a high melting point, such as metal, is mixed and coated during the process with a material with a lower melting point, such as nylon, allowing the laser to only melt the material with the lower melting point in order to fuse the granules into a solid. The most common of these composites is the â&#x20AC;&#x2DC;alumideâ&#x20AC;&#x2122;, a plastic powder mixed with aluminium, making

possible to print metal sparkle at relatively low temperatures. SLS is a very precise process, producing detailed results when printing in plastic materials, but the sintering of composite powders cannot produce parts with high performances suitable for engineering applications. For this reason different variations of this technique has been developed, which take advantage of lasers or electron-beams to fully fuse granules of a single material, in order to produce purer metal objects.

2.3.3 SELECTIVE INHIBITION SINTERING (SIS) Industrial additive manufacturing (AM) machines offer a variety of materials, including high-performance metals, with printed parts capable of tackling industrial applications. Unfortunately, these machines come at a high cost. A novel AM process called selective inhibition sintering (SIS) for use in a consumerpriced metal AM machine has been developed

by Dr. Behrokh Khoshnevis and his team at the University of Southern California. This new method of printing is basically the inverse of selective laser sintering and other forms of metal printing. Research in powder sintering is usually focused on implementation of the sintering process. Similarly, the metal-based AM

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

processes described above selectively sinter, or fuse, powder within each layer’s part cross section. On the other side, the Selective Inhibition Sintering process, is based upon the retardation of sintering. In fact the principal innovation behind the SIS technique is the prevention of selected regions of each powder layer from sintering, achieved by operating on the regions external to the part in each layer with a “sintering inhibitor”. A commercial piezoelectric printhead is utilized to deposit a liquid chemical solution (inhibitor) at the periphery of the part for each layer. When all the layers have been treated, the entire part is removed from the machine and bulk sintered in a conventional sintering furnace. The inhibitor deposited at the part’s boundary decomposes into hard particles that impede the sintering process. The particles in this region are prevented from fusing, allowing for removal of inhibited boundary sections and

revealing of the completed part. It is easiest to think of the part as if it were encased in a sacrificial mold. The SIS technology brings many advantages, making it both precise and inexpensive. In the first instance the use of a commercial printhead instead of expensive laser or electron beam generators drastically reduces costs; parallelly, the process is faster since only the boundary of the object is worked and there’s no need for support removal since they are, if needed, attached to the ‘sacrificial mold’. Moreover, SIS-printed objects are purely of metal, without any sort of binder or residue, making them stronger than contaminated parts and avoiding contamination of the sintering furnace (Khoshnevis et al., 2014). Being still an experimental technique, selective inhibition sintering process is not ready yet for commercialization but it’s a promising opportunity for cheaper metal-AM working.

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THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.4 LIQUIDS PHOTOPOLYMERIZATION Photopolymerization processes make use of liquid, radiation curable resins, or photopolymers as their primary materials. Most photopolymers react to radiation in the ultraviolet (UV) range of wavelengths, but some visible light systems are used as well. Upon irradiation, these materials undergo a chemical reaction to become solid.

This reaction is called photopolymerization, and is typically complex, involving many chemical participants. Photopolymers were developed in the late 1960s and soon became widely applied in several commercial areas, most notably the coating and printing industry.

2.4.1 STEREOLITHOGRAPHY (SLA) In the mid-1980s, Charles (Chuck) Hull was experimenting with UV curable materials by exposing them to a scanning laser, similar to the system found in laser printers. He discovered that solid polymer patterns could be produced. By curing one layer over a previous layer, he could fabricate a solid 3D part. This was the beginning of stereolithography (SLA) technology. The company 3D Systems was created shortly thereafter to market SLA machines as â&#x20AC;&#x153;rapid prototypingâ&#x20AC;? machines to

the product development industry. Since then, a wide variety of SLA-related processes and technologies has been developed. SLA creates solid parts by selectively solidifying a liquid photopolymer resin using an UV laser. As with many other AM processes, the physical parts are manufactured by fabricating cross-sectional contours, or slices, one on top of another. These slices are created by tracing 2D contours of a CAD model in a vat of photopolymer resin with a laser, causing it to

â&#x20AC;&#x153;cureâ&#x20AC;? (setting solid). The part being built rests on a platform that is dipped into the vat of resin. After each slice is created, the platform is lowered, the surface of the vat is recoated, then the laser starts to trace the next slice of the CAD model, building the prototype from the bottom up. As in material extrusion, objects 3D printed using stereolithography often require additional structures to be added to them to support overhangs or initially orphan parts. These supports then need to be broken away by hand or cut out with tools after printout. Objects need then to be cleaned with a solvent and then with water, to get a completely clean object.

Additional post-processing may involve curing in a UV oven, blasting with glass beads or varnishing to prevent discolouration if theyâ&#x20AC;&#x2122;re gonna be exposed to sunlight. Materials portfolio was initially limited to just brittle resins, making the technology suitable just for the production of masters from which molds would be taken, or else for visualization purposes. In last few years, however, a far wider variety of stereolithographic photopolymers have been developed, including rubber-like plastics, totally clear resins, substitutes for ABS and other thermoplastics, flame-retardant plastics and even special photopolymers

figure 2.9 Stereolithographic printer. The viscosity and surface tension of photopolymeric liquids allowed the development of machines where the fabricated object is held upside down in the polymer bath

suitable for jewelry or dental modelling, one of the main markets for the technology. This is therefore leading from mold masters or preproduction models production to the manufacture of final products ready for use. Objects manufactured with SLA technology are very accurate, far more than filament extrusion, giving form to objects with smooth surfaces, without any ‘stepping effect’. The largest SLA printers can, at the time of writing, print layers 0.05 mm thin, with an accuracy of 0.025 on X and Y axes, and a build volume up to about 1500 x 760 x 560 mm (Barnatt, 2013). This process has been for years just closed to industrial practice, but from 2010 different

companies tried to change the trend and produce desktop stereolithographic printers with smaller build prices but also smaller prices, affordable for common users. At the moment of writing, SLA printers prices ranges from about 3000€ for the cheapest desktop printer (DWS Systems - X Fab) to 500000€ (3DSystems) for the most expensive large industrial 3D printer. Unfortunately the price of photopolymers does remain far higher than that of build materials used in thermoplastic extrusion, starting from about 100€/Kg.

figure 2.10 Japanese company Unirapid Inc developed a small SLS 3D printer called Unirapid III. The image is an example of its possibilities: a small cube 2.5 x 2.5 x 2.5 mm printed in high resolution with ABS-similar material for 32 minutes

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.4.2 DIGITAL LIGHT PROCESSING (DLP) A second technique taking advantage of the principle of photopolymerization is DLP projection. Usually, DLP technology is found at the core of video projectors used in lecture theatres, schools, cinemas and some homes. It features small imaging chip that include an array of microscopic mirrors (“Digital Micromirror Devices”, DMD), which can be rapidly rotated, allowing them to reflect light out of the projector lens onto a heat sink. This technology has been recently exploited in 3D printing since DLP projectors can be used to selectively solidify a photopolymer liquid. The DLP device is positioned above a liquid tank and is used to harden a complete layer of the object on the surface of the liquid. Similarly to SLA technology, the printer’s build platform is then lowered, and another layer is hardened by the projector until the entire item has been

printed. The same set of photopolymers employed in stereolithography 3D printing can be used and similar high level of accuracy can be achieved, with the difference that higher precision can be obtained in smaller printers rather than in big ones, as the projector image only need to be focused on a smaller area. A large current DLP projection 3D printer have a minimum layer thickness of about 0.025 mm and a build volume of 267 x 165 x 203 mm. Good advantages of DLP projection 3D printing with respect to SLA is that components, such the projector, are less expensive and requires less energy to run, making this technology more suitable for a desktop use. Contemporary, printing one entire layer at the same time make the process much faster than SLA technology which has to harden point by point the liquid.

figure 2.11 A sculpture by Amanda Darby developed through digital light processing using the Envisiontec Perfactory 3D printing system

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.4.3 MULTI JET MODELLING (POLYJET) PolyJet printers are the youngest members of the deposition branch of the printer family, developed in 2000 by an Israeli company called Objet Geometries (which merged with Stratasys in 2012). PolyJet printers borrow technologies from both major branches of the 3D printer family tree, combining a printhead that sprays liquid photopolymer into extremely thin layers and firms up the photopolymer with a bright UV lamp. With the PolyJet method, the layers of the part are created with individual drops of material that are deposited onto the work platform. The printhead holds numerous nozzles that are arranged across the width of the platform. The light source for curing the material is mounted directly behind the print nozzles. The model area along the X axis is covered by the nozzles; the printhead runs along the Y axis, the so-called pass. Building up the height of the model is achieved by lowering the work platform. Immediately after one layer

is complete, the deposited material is cured with ultraviolet light. In a secondary step, a roll smoothes the layer surfaces, onto which the next layer is deposited during the following pass. All of the material needed for one layer is pushed out of the nozzles simultaneously. The material used is an acrylic photopolymer. The necessary support structure is printed with a secondary row of nozzles. It consists of a gel-like material that, after completion, is removed by water jetting. The layer thickness is about 0,016 – 0,030 mm and guarantees a very precise and smooth surface; eliminating the need to rework for most applications. Since the material is deposited in individual particles, the final resolution is very high. With the PolyJet technology it is possible to mix numerous gradients of the two original materials directly onto the process platform, using so-called “digital materials”. Thus, different areas of the part can feature different material properties. We know this from handles with hard as well as

figure 2.12 A design for a helmet called Pneuma 1 designed by Neri Oxman. Implements novel multi-material 3-D printing technologies along with new design features such as bitmap printing and property textures have been developed to support material performance and expression

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soft parts, for example, or remote controls with a hard casing but soft buttons. This is of great advantage for realistic prototype production (for example for flexible joints, rubber soles, springs). Even though it is not yet possible to print the materials in a true gradient, meaning with seamless transition, current technical feasibility already points toward the next step: programming true seamless gradient materials.

A major downside of PolyJet printing lies in inherent limitations in the printing material it uses, a type of plastic called a photopolymer. Photopolymers are highly specialized, expensive plastics that respond to UV light. Plastic can be one of the most coarse manufacturing materials there is, but most photopolymers are still relatively fragile and brittle, which limits their range of applications.

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

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THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.5 PRINTING-MATERIAL ENGINEERING Earlier AM technologies were built around materials that were already available and that had been developed to suit other processes. However, the AM techniques are somewhat unique and these original materials were far from ideal for these new applications. For example, the early photocurable resins resulted in models that were brittle and that warped easily. Powders used in laser melting processes degraded quickly within the machine and many of the materials used resulted in parts that were quite weak. As we came to understand the technology better, materials were developed specifically to answer the needs of different AM processes. Materials have been tuned to suit more closely the operating parameters of the different processes and to provide better output parts. For example, concrete printing processes are limited by the curing and drying time of the material, thus researchers are trying to improve the chemical reaction which produce the curing

of concrete by varying the composition of the aggregate. As a result, parts are now much more accurate, stronger, and longer lasting and it is even possible to process metals with some AM technologies. Moreover, these new materials have resulted in the processes being tuned to produce higher temperature materials, smaller feature sizes, and faster outputs (Gibson et al., 2014). Unfortunately is not possible to 3D print with every material. For instance, it is the case of plastics, since it is not possible to use other than thermoplastics, that becomes pliable or moldable above a specific temperature and solidifies upon cooling, not giving the possibility to take advantage of common fibre reinforced plastics or similar strong plastics already constantly used in engineering and architecture. Consequently, we can definitely state that additive manufacturing technologies requires specific materials to produce effective results. Research is constantly conceiving new material

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variations for 3D printing in the attempt of optimizing their performances, reducing costs and closing the gap between additive manufacturing and end-use products. This need is at the same time a great potential for AM, since a whole new branch in material engineering is growing to study materials for 3D printing and it is increasingly thinking up new, stronger and customized materials which canâ&#x20AC;&#x2122;t be used with other existing manufacturing processes.

Additive technology grant a growing range of materials to produce objects, but apart from this indirect improvement, the process of adding material itself is opening to a whole new scenario, the possibility to organize materials and their properties over the object volume during printing. The opportunity of gradually varying, for instance, the elasticity of an object over its section, would be almost impossible with different manufacturing techniques, and has an infinite potential for customization and optimization.

THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

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THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

2.6 THERE IS NOT (YET) A 3D PRINTER FOR ARCHITECTS Does it exist a 3D printer for architecture? Which are the features of the ideal 3D printer for construction and architecture? Every additive fabrication approach brings advantages and disadvantages in its process. Extrusion-based machines are usually not expensive, and also material used are commonly cheaper than other additive technologies, however often demonstrating good mechanical properties; on the other side they do not allow for great precision with respect to other processes, and they have formal limitations in overhanging structures. Differently, all those technologies which include laser beams results generally more expensive, both in machines, materials and maintenance costs, although guaranteeing an incredible design freedom and precision. A building construction process as we know it today is made by dozens of different machines, working at different scales, with different materials and different roles into the incredibly

complex realm of constructions. Therefore it appears ambitious to define a unique model of fabrication for a whole building, but it is more convenient to think that additive manufacturing may be integrated in traditional construction operations, and that different additive techniques may be employed for different applications. From this technological review it is nevertheless evident that additive manufacturing in general is a technology still under dramatic development, which started being fruitful and productive for experimental applications but that seems not yet ready for a huge, complex and competitive market such as constructions. Furthermore, it is noticeable that additive fabrication processes have not been investigated for architecture and constructions as much as in other other fields, such as design, but also aeronautics, where small objects, in small series but with incredible details appears to be an immediate advantage.

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THE (SEVERAL) MATERIALS AND TECHNIQUES OF ADDITIVE MANUFACTURING

REFERENCES Barnatt, C. (2013) 3D Printing: The Next Industrial Revolution. CreateSpace Independent Publishing Platform. Deekard, C. R. (1989) Method and apparatus for producing parts by selective sintering. US Patent: 4,863,538. The University of Texas System, Austin, Tex. Gibson I., Rosen D., Stucker B. (2014) Additive Manufacturing Technologies. Springer, NYC. Karunakaran, K.T. et al (2012) Rapid manufacturing of metallic objects, in Rapid Prototyping Journal. Torabi, P., Petros, M., Khoshnevis, B. (2014) Selective Inhibition Sintering: The Process for Consumer Metal Additive Manufacturing. 3D Printing and Additive Manufacturing. September 2014, 1(3), pp. 152-155. Wikinvest (2014) Stratasys, Annual Report. http://www.wikinvest.com/stock/Stratasys_(SSYS)/Products. Accessed 29 December 2014.

CASE STUDIES OF 3D PRINTING IN ARCHITECTURE

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CASE STUDIES OF 3D PRINTING IN ARCHITECTURE

3.1 CLASSIFICATION METHODOLOGY A study of the major additive manufacturing processes gave a comprehension of the technological framework of the thesis. The following chapter, consequently, will investigate a selection of relevant case studies of applications of layered manufacturing technology in the architectural and building construction context. Every project involves a choice of the production technique, materials, the scale of the building and the function of the manufactured elements within it. The fact that is difficult to find two projects which shares all these aspects shows already that the technology is far from a full development and a clear definition into the architectural field. For example, various projects shares PLA plastic as printed material, but applications of manufactured elements are different, from bricks to shaft structures or molds, as well as production techniques, which ranges from SLA printers to custom robotic

arms. Consequently, this analysis would give us a better understanding of the potentials and the weaknesses of every approach, clarifying the emergent trends among them. In the previous chapter, technology has been classified according to the initial state of the material used during the printing operation. Since the goal of this research is the final application of the process, in this chapter an overturn of the perspective is needed. The focus is shifted from production to application, from technology to architecture. The selected case studies have been subdivided according to the approach of designers towards the application of layered manufacturing technologies in their architectural projects and construction processes. Since most of the projects are on-going researches which aims at studying, developing or demonstrating a viable use of additive manufacturing fabrication more than providing ready-to-use solutions for everyday

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architecture, each of the research team, designers and engineers propose a defined strategy of use of AM to be helpful to improve design and construction, which often goes beyond technological limitation of nowadays printers. This approach, which puts together and goes beyond dimensions and materials, both often limited by temporary technological limits, or final use of printed elements, will be the main driver in the classification, and analysis, of the projects. In particular resulted four main concepts: joints, components, monoliths and molds.

Every project is going to be analysed focusing on the design approach, trying to understand why and how an additive manufacturing process has been taken into account, together with the fabrication method conceived, studied and tested, and on the materials used. Finally the scientific relevance of the project, together with its weaknesses will be discussed. The investigation aims at giving a clear understanding of the actual possibilities as well as the limitations of the aforementioned technique, providing indications for possible future research directions both in printing technologies, material engineering and design.

CASE STUDIES OF 3D PRINTING IN ARCHITECTURE

3.2 PRINTED JOINTS The first set of projects is characterized by the use of additive manufacturing in the fabrication of joints for building structures. Usually they are small in size which makes them particularly suitable for the application of 3D printing in architecture, not requiring a specific machine with peculiar dimensions or mechanical characteristics of the material. They can be compared, in dimension and mechanical

requirements, to aeronautical or automotive engineered parts that have already been studied and produced in small series through additive manufacturing processes. The application for joints of such a technology seems particularly intriguing for its precision but in particular for the possibility to make each piece different from the other, a great advantage in complex structures.

3.2.1 3D PRINTED STEEL JOINTS | ARUP London, 2014 In the beginning of 2014, a team headed by Arup, revealed a project for 3D printed structural steel joints. The collaboration with the engineering design software and consulting company WithinLab, but also with CRDM/3D Systems and EOS as additive manufacturing experts brought to a proposal for steel nodes

for lightweight structures characterized by complex shapes and customized design. Made from maraging steel, each of the 14-centimetre-tall prototypes is produced at just under half the size of a real node and has been put through preliminary material tests.

figure 3.1 A close-up image of the 3D-printed steel joint developed by Arup, revealing the complex geometry and the customized design

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The original nodes have been conceived in stainless steel and later produced with maraging steel, compatible with the technology of the machine owned by the partner CRDM. The process is based on the principle of additive laser sintering, employing steel derivatives as printing material. This material is about four times stronger than normal construction steel, which made Arup eager to experiment with it and further explore its potentials. EOS, the additive manufacturing company involved in the production of the steel elements, reported that this technological solution guarantees, at the moment, a 40% reduction of CO2 emissions over the whole lifecycle in respect to traditional casting processes. Due to the nature of the

technique, the production waste materials is minimized, furthermore making possible a great geometrical freedom and a reduction in weight. The consumption of titanium is reduced by 25% compared to the traditional casting method. Testing prototypes were scaled down to 40 % of the original size, thus being 14 cm high, without compromising the structural properties of the joints, in order to verify and improve this method. Arup imagined to develop their technology in the application of large sculptures, as an intermediate test before using it in buildings (Arup, 2014).

figure 3.2 Left: Original steel joint produced with traditional technologies; Right: Arup optimized Steel joint fabricated with Direct Metal Laser Sintering (DMLS) additive technology

CASE STUDIES OF 3D PRINTING IN ARCHITECTURE

3.2.2 3D PRINTED NODES SHROUDS | FLETCHER PRIEST ARCHITECTS London, 2008-2014 In 2008 Fletcher Priest Architects designed a mixed-use building located at 6, Bevis Marks in the City of London, with main contractor the construction firm Skanska. The project integrates an 1980s structure providing nine additional floors and three private terraces, including a sky court on the rooftop. Innovative in the intervention is the application of additive manufacturing for the structural system. An important challenge in the project was to produce smooth geometry for steel canopy framework structural system which form a group of branched columns. One of the driving ideas of the project is the connectivity in both metaphorical and physical sense. Streets and outdoors spaces of the existing have been reconnected with the City through the new intervention, the facade as well connects adjacent buildings relating the project to the existing environment. The rooftop assumes both a symbolic and functional role

with its covered garden, providing a solar shading to the South-West elevation, defining the southern elevation as well, and parallely creating a link between open terrace and lower levels. The roof terrace is characterized by a steel structure of branched columns, that supports a lightweight canopy made of ETFE pneumatic cushions fixed to a continuous system adapting itself to the underlying supporting structure. Considering the role of new technologies in architecture, the principle of customization that stands behind the roof canopy is particularly interesting. A series of 3D printed sheaths were designed to surround the structural joints that connect the steel columns and the respective branches supporting the ETFE canopy. The structural constraints deriving from the existing building determined a specific design for each structural joint of the roof, requiring a unique and rigorous form finding process to achieve

figure 3.3 The steel canopy framework system which forms a group of branched columns designed by Fletcher Priest Architects

an elegant structural solution that is coherent and integrated with the design language of the building. With the aim to reach the desired aesthetic specifications for the rooftop joints, several manufacturers and fabricators have been involved in the project. Starting from the intent of a traditional process of steel casting, the use of 3D printing technology was considered as it offered optimization in terms of time and cost. 3D modeling was employed to simulate the complex and organic shape of the joint sheaths

and to extract the required information later transferred to the printing machine. The use of mass-produced customized sheaths constituted an innovative and optimal solution to coherently integrate the structural elements with the building design language. Furthermore, the production process allowed to fabricate the components at more affordable prices in respect to the traditional methods. To achieve a satisfactory solution, an iterative process alternating digital and physical simulations was adopted: during the design

figure 3.4 The picture shows the rooftop steel joint covered with the 3D printed polyamide sheaths

phase mock-ups were developed in order to inspect the aesthetics of the elements and to ensure a smooth construction process on site. The sheaths fabrication was realized by Selective Laser Sintering (SLS) employing polyamide 12 as a material to produce the joint covering components. This material is a specific type of nylon particularly suitable for exterior application as it is resistant to ultraviolet radiation and offers filtering properties. It is able to absorb moisture and gain strength over time

even if it needs to be waterproof before being used for outdoors. In this case, the 3D printing machine size constituted a limitation as the nodes needed to be printed in sections before being applied to cover the canopy joints. This case represents a concrete and feasible solution to provide specific architectural language and technological performance with the potentiality enabled by the emerging additive manufacturing process.

figure 3.5 Digital model of the system integrating columns within the 3D printed shroud for the structural joints

CASE STUDIES OF 3D PRINTING IN ARCHITECTURE

3.3 CONSTRUCTION COMPONENTS This set of cases comprises all those projects and researches which envision and apply additive manufacturing in architecture in the production of building components. The domain of dimensions of such elements is very different, passing from bricks to rooms, but all the projects have the common vision of an assembly of 3D printed objects. The advantage

of this choice relies in the transportability of pieces, but also in the possibility of taking advantage of existing additive machines without the need to invent a new fabrication process. Moreover, construction components can capitalise on 3D printing capability of fabricating different shapes without limitations to improve assembly systems and tessellations.

3.3.1 CUSTOMIZED CERAMIC BRICKS: BUILDING BYTES & POLYBRICKS Amsterdam, 2013 & Ithaca, 2014

“Bricks are an ancient building component and their fabrication has seen several innovations throughout history. The fabrication, however, has consistently relied on moulds or simple profiles which were produced on brick extrusion machines. Building Bytes explores the new design and material possibilities offered by the use of 3D printers for the fabrication of bricks.” (Brian Peters 2012) The production of ceramic blocks and tiles has a vast technological and design history. Ceramic modules of standard measurement have been used as a building block and replacement of

stone for centuries. Contemporary interest in the ceramic module and technical advancements in prefabrication have offered prefabricated non load-bearing brick façades. Consequently,

figure 3.6 Top: A new technique for fabricating ceramic structural components through the use of desktop additive manufacturing machines developed by Brian Peters (DesignLab Workshop) Down: It takes around 15 minutes to print the parametrically designed bricks

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different studies has been undertaken to couple ceramic and additive manufacturing technology. (Sabin et al. 2014) Of particular interest is the Building Bytes research project, led by Brian Peters (DesignLab Workshop), that proposes a new technique of fabricating architectural components, in particular ceramic bricks, through the use of common desktop 3D printers, which become “portable and inexpensive brick factories for large-scale manufacturing” (Peters 2012). The project seeks to investigate the possibility to fabricate potentially infinite typologies of a traditional construction component, the brick, studied and re-invented thanks to the contemporary additive manufacturing technologies. The common base is the material: the bricks are all made from a liquid slip cast solution of earthenware ceramics, which fits the technology in use, being semi-liquid, therefore both extrudable and controllable. Every brick has been designed using parametric software (Grasshopper) that allows quick visualization of the various design options,

providing also informations regarding cost, printing time and position within the full scale assembly of every single brick. Rather than designing, engineering and constructing an expensive custom printer, Building Bytes project using a standard FDM desktop 3D printer, simply with a modification of the extrusion system, developed to arrange any liquid material, consisting of plastic cartridges and air pressure. These types of machines are inexpensive and widely available on the market with a relatively small printing size: approximately 20 × 20 × 20 cm. However, within this research the printing dimensions were not considered as a limitation but rather one of the design parameters that characterized the final production. One of the main challenges of the research was the desire to use ceramic materials, which meant the specific configuration of a desktop machine. Focusing on this purpose, the plastic extrusion system, also defined as the “print head” of a standardized 3D printer, was replaced with a bespoke one that worked with air pressure. Several recipes were tested throughout its execution in order to define

CASE STUDIES OF 3D PRINTING IN ARCHITECTURE

the ideal viscosity, drying time and shrinkage of the composite. The final printed material was derived from a cast recipe of earthenware ceramics extruded through the air pressurized “print head”. During printing, the required speed for extrusion, related to the air pressure, was constantly monitored to ensure a continuous extrusion process. The printing path followed a series of overlapping layers constituted by a printing path polyline that needed to be continuous and unbroken to ensure structural stability. The printing process lasted about 15–20 min for each brick, and in the end each printed component needed to be air dried for 1 day and then fired in a kiln at 1,100 °C for 12 h. (Naboni and Paoletti, 2015) Building Bytes is the first research which shows the potential of desktop cost-effective 3D printers in the production of new designs for bricks using a traditional material such as ceramic, using parametric software to model infinite options and control production data. Parallelly, Sabin Design Lab, in Cornell University, developed a research which experiments the use of algorithmic design

techniques for the digital fabrication and production of nonstandard ceramic brick components for the mortarless assembly and installation of 3D-printed and fired ceramic brick wall. (Sabin et al., 2014) Rather than designing massive parts, they implemented a structural lattice to achieve an array of linked components, which allowed for a high degree of resolution in each part maintaining strength while saving on material usage. As Jennifer Sabin, Sabin Design Lab leader, said, 3D printing allows to build and design like nature does, where every part is different, but a coherence to the overall form. This is the goal of their research, together with trying to achieve a system that requires no additional adhesives or mortar, looking to traditional wood joinery techniques as a means of interlocking adjacent components. They developed a customized tapered dovetail in which the direction and severity of the tapering is dependent upon the local geometric orientation of each component; the tapering of the dovetail is based upon the slope of the surface being generated such that the narrow end of the tapering is always at the

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lower face of the generated surface. Thus, the force of gravity locks adjacent components together. The actual clay modules in the project were directly printed using a ZCorp 510 color powderbased binder jetting 3D printer, exchanging the proprietary ZCorp powder media for our custom clay body recipe, which is drastically more cost effective. Initial recipes for the dry clay mixture were adapted and later transformed from open source recipes published by Mark Ganter who directs the Solheim Rapid Manufacturing Laboratory located in the Mechanical Engineering Building at the University of Washington in Seattle. (Sabin et al. 2014) After cleaning the greenware printed bricks, they are fired to a low initial bisque fire, then subsequently dipped in a high fire satin

glaze. Finally, the bricks are fired to a higher temperature in order to ensure that the glaze vitrifies. Testing several means for the generation of clean mesh component models, they developed a reliable system utilizing parametric design tools within the Grasshopper plugin for the Rhinoceros 3D modeling software. (Sabin et al., 2014) This experiment is of particular interest for the adaptive interlocking system they studied and developed which tries to solve with a smart solution, without adding any mortar or external support. Moreover, reduction of costs and increasing in performances through alteration of material and binders is an interesting aspects, which shows the importance of material engineering into 3D printed architecture.

figure 3.7 Non-standard ceramic brick components for mortarless assembly developed by Sabin Design Lab, in Cornell University

CASE STUDIES OF 3D PRINTING IN ARCHITECTURE

3.3.2 QUAKE COLUMN | RAEL, SAN FRATELLO San Francisco, 2014 The California-based architecture firm, Emerging Objects, is taking on in the construction industry using 3D printing technology in innovative ways. In 2014, after a 5 year of exploration over materials, Rael and San Fratello designed Quake Column, a 3D-printed design based on Incan techniques used to create seismically resistant structures. What’s especially interesting is that the designers didn’t set out to design such typology of structural system. Instead, it came out of a study over materials, in the attempt of using sawdust, ground-up tires, salt, and pulverised bone into effective, if strange, construction materials. Emerging Objects’ principals - Ronald Rael, an Associate Professor of Architecture at the University of California, Berkeley and Virginia San Fratello, an Assistant Professor of Design at San Jose State - take the pursuit of novel

materials seriously. Together with a 10-person team, they have begun fabricating small objects, like tiles, screens, and home goods, but are quickly scaling production capacity to match their architectural ambitions. The architects produced a structure with interlocking pieces using ashlar technique. Like California, Peru is “highly seismic”, and the Incas had their architecture fine-tuned to work with seismic events rather than against, eschewing mortar and instead creating dry stone walls with interlocking pieces, inclining inwards by 3° to 5°, with rounded corners. These stones were massive and heavy. Their architectural designs were meant to diffuse seismic force. It’s an interesting proof of concept, but utilising a 3D printer, rather than traditional ceramic manufacturing technique also unlocked a host of other advantages. The bricks are hollow, creating a high strength-to-weight ratio. Each brick is printed with a code that

figure 3.8 Quake Column is made of 3D-printed interlocking components, creating a seismically resistant structure

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explains to the mason how the bricks should be configured. Moulded handles in each brick make on-site assembly as easy as snapping together Legos. And according to the architectâ&#x20AC;&#x2122;s

calculations, this technique could be used to fabricate building code compliant load-bearing walls.

figure 3.9 Left: The project is the result of a long research focusing on the idea of reusing waste and turning it into effective construction material Right: The bricks are hollow and moulded with handles so that they can be easily assembled

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3.3.3 PLASTIC PAVILIONS: ECHOVIREN & PROJECTEGG San Francisco, 2014 & Eindhoven, 2014 Two different projects tried to work with plastic small components. In the August of 2013, the californian studio Smith | Allen participated in the Project 387 Residency, in Mendocino County, where, in the heart of a 150-acre redwood forest, they designed and created a site-responsive, 3D printed architectural installation, named Echoviren. The project wants to merge architecture, art and technology in an exploration between man, machine and nature: the pavillion is site-responsive, mimicking and abstracting the xylem and phloem of the lush life that surrounds the built piece. At the same time its white translucency strongly contrasts the natural environment characterized by reds and greens of the forest. Spanning approximately 3 x 3 x 2 meters, Echoviren is composed of 585 interlocking components, printed over the course of 10,800

hours. (Smith | Allen 2013) Echoviren was fabricated taking advantage of a cluster of consumer grade Type A Machines desktop 3D printers and completely assembled in four days within the forest environment. The pavillion is a composition of plant-based bioplastics, which allow the form to decompose and create myriad micro-habitats as the walls integrate into the ecosystem. Same material and same technology with a different approach has been used by the dutch designer Michiel Van der Kley, who in 2014 saw the opportunity to produce a building with stones that were each different, and, particularly interesting, with a lot of people from the community of 3D printers all around the world involved in the production process. (Van der Kley, 2014) The ProjectEGG pavillion has an irregular ellipsoid shape, measuring roughly 5 x 4 x 3 meters, made of 4760 different stones. It has

figure 3.10 The site-responsive, mimicking 3D printed architectural installation, named Echoviren, designed by the Californian studio Smith | Allen

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been presented for Dutch Design Week 2014 in Eindhoven. The particular idea behind the fabrication is that it has been an “open” process, involving everyone who wanted to collaborate, uploading on the project website the files for each piece to be printed, and giving the opportunity to print and send a piece, participating in the creation of the “building”. The space does not have a function, because it was not the main issue in the project. Its purpose is to show other people what 3D printing is capable of, trying to show that maybe we’re entering in a new revolution in the way we produce, the way people can get evolved and the democratization of the building process. Rhino and Grasshopper has been used to model the whole shape and then each piece, adding holes for screws and labels. Similarly to Echoviren installation, each stone of ProjectEGG is made of PLA (polylactide) plastic, a material which is both biodegradable and commonly used for 3D printing technology. the construction allows for limited material usage, with pieces attached by custom

hexagonal screws. Each element can be printed by a common desktop 3D printed without the need of any supports. Over 20 different brands of FDM printers were used by many people around the world to build the pavillion, proving both the productivity of a collaborative approach and the possibility to make large things with small machines. This two examples are among the first attempts to build large elements with small, cheap, common 3D printers, using an assembly of small elements, and they highlight potentials and limitations of this approach. Costs of both materials, machines and operative expenses such as transportation are reduced to the minimum, enabling to build large spaces without the need of huge, expensive and non-movable machines; on the other side the large number of components put some limitations and obstacles in the construction process, needing thousands joints which are potential weakness in the structure, and the plastic materials are still not ready for structural elements in building construction.

figure 3.11 The ProjectEGG pavillion has been developed as an “open” process involving people from the 3D-printing community from all around the world and as a result comprises 4760 different components

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3.3.4 3D PRINT CANAL HOUSE - DUS ARCHITECTS Amsterdam, 2014 In the first months of 2014 the Amsterdambased architectural firm DUS Architects has finally opened to the public a new project: the 3D Printed Canal House. The project is an exhibition, research and building site for 3D Printing Architecture. The idea is to 3D print a full-size canal house in the very heart of Amsterdam, trying to show the world how to combine tradition, redesigning one of the symbols of the city, with new innovative ideas, trying to investigate what this traditional architype can be in a 21st century context (DUS Architects, 2014). The house, located in the developing northern area of Amsterdam, works as an open center of research in 3D printing at the architectural scale: the large-scale 3D printer is located on the construction site, and every printing process is open to the public. The site opened its doors to the visitors in March 2014, becoming a learning space, rich of

public events, lectures and workshops, where everyone has the possibility to learn about 3D printing and architecture. The project evolves its configuration according to newly developed solutions, the design modified in accordance to new discoveries about fabrication process, material tests and mechanical responses, in a constant â&#x20AC;&#x153;learn-by-doingâ&#x20AC;? development. In the project, the 3D Print Canal House envisions several rooms made up of different elements designed with 3D modelling techniques, printed and assembled on-site. Every area is firstly printed at 1:20 scale to be tested and verified, and later printed at full scale for the assemblage: this process highlight the strong possibility given by additive manufacturing techniques of scalability of the model, where everything can be scaled with comparable properties.

figure 3.12 3D Printed Canal House by DUS architects is a progressive research aiming at 3D printing a full-size house, exhibiting the results from combining tradition and innovative technologies

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The printed chunks constituting the house contain hollow areas for pipes and wirings, designed to be later filled with a second reinforcement and insultion material. Both digital software and physical testing are constantly employed and improved for structural aspects, in collaboration with engineers from Tentech. The design teams have experimented supporting elements that developed inclined shafts, and to improve overall structural performances, some elements are shaped with folds. The latest printed structural elements contain a double layer of shafts, in perpendicular directions, to improve structural behavior. Every pieces of the Canal House Project is printed thanks to the so called KamerMaker, literally â&#x20AC;&#x153;room makerâ&#x20AC;?, a large-scale version of a portable desktop 3D printer. It is contained in a movable shipping container and is the result of the collaboration between Ultimaker, Fablab Protospace and

DUS Architects, among others. The printer is approximately 6 m high and can print objects as large as 2.2 x 2.2 x 3.5 m3, allowing architects to fabricate entire 1:1 scale components directly employable as building elements. The granulate material that feed the KamerMaker, is a bioplastic called Macromelt, a type of industrial glue. It is made of 80% of vegetal oil and melts at 170 degrees celsius: being homogeneous and stable, but also sustainable, of biological origin, and melting at relatively low temperature, the product developed by the german chemical firm Henkel, meets all requirements of the architects. (DUS Architects, 2014) At the moment plastics proved to be the most immediate material for additive manufacturing developments, but the aim of the research is different from simply demonstrating the potential of plastics for housing construction, and architects and constructor plans to test and compare a wider range of materials for the printing process.

figure 3.13 Top: 3D Printed Canal House features a large-scale 3D printer, located on the construction site and exhibiting every printing process to the public. Down: The concrete casting: increases the compressive structural capacity and joins the separate pieces together through inclined shafts

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3.4 MONOLITHIC STRUCTURES A rather ambitious approach towards 3D printing in architecture is the idea of using additive fabrication to print massive monolithic structures, with the aim of constructing entire buildings using such a technique. Every project

however retains its peculiar features, aiming at stressing on different perspectives: complexity and definition of printed parts, large fabrication scale or speed of production.

3.4.1 DIGITAL GROTESQUE - HANSMEYER, DILLENBURGER Zurich, 2013 Existing large-scale 3D printing technologies can only print simplified shapes with rough details, while high-resolution possibilities are limited in print spaces, material properties and high costs. Hansmeyer and Dillerburger research focuses on recent developments on sand-printing technology, presenting a specific experiment, Digital Grotesque project, which tries to exploit the full potential of the technique. As a fictive narrative space, the project is less concerned with functionality than

with the expressive formal potentials of digital technologies. It examines new spatial experiences and sensations that these technologies enable. Digital Grotesque is a realized space, consisting of two individual halves that form an aggregate volume: the grotto. It is a cubical mass, but its interior reveal an intricate geometry of millions of design facets. The structure is divided in eight elements, each restricted to the maximum dimension of a 120 x 120 cm pallet, where they can be though

figure 3.14 Digital Grotesque project focuses on the recent developments on sand-printing technology and tries to exploit the full potential of this technique

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easily transported. Each section’s weight was minimized in order to make them more compliant and to reduce the load of the overall structure: thickness of the wall was reduced to one centimeter in non-critical areas and each piece has been hollowed out. Moreover they have printed details for lifting and for joining with neighboring pieces: truncated cones for vertical alignment, horizontal and vertical shafts, allowing reinforcements and bars for lifting. Digital Grotesque has been designed through an algorithmic procedure called “meshgrammars”, which procedure consists of rules that articulate the structure out of a primitive input form, by recursively splitting surfaces. The process allows for highly specific local conditions with complex topologies to be generated. (Hensmeyer, Dillenburger, 2013) The final mesh, consisting of 260 million points, was printed with the sand-printing

technology by VoxelJet, which combines high accuracy and resolution with a large printable space: the structural capacity of this fabrication technology is of 220-250 N/cm² bending strength, with a resolution up to 0.13mm layer height and a speed of 3 cm per hour for a 4 x 2 meter layer area. (Hensmeyer, Dillenburger, 2014) The project demonstrates the potential and precision of sand-printing technology, which allows otherwise nearly-impossible designs and details. With the technology used cost of complexity disappears, and at the same time opens of infinite possibilities both in aesthetics, functional and structural fields of design. On the other side some challenges remain, such as a need for deeper studies on materials and binder in use, to generate stronger, lighter and more durable components for complex non-standardized architectures.

figure 3.15 The project demonstrates the precision and the potentials of sand-printing technology and the possibilities it offers in terms of complexity, reduced fabrication cost and aesthetics.

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3.4.2 VILLA ROCCIA PROJECT | JAMES GARDINER, D-SHAPE Porto Rotondo, 2009-2012 Sand has been used for a large-scale 3D printing project by D-Shape, company and technique developed in 2004 by the Italian engineer Enrico Dini. The founder of the enterprise lodged his first construction 3D printing technique patent in 2006, when the project relied on synthetic resins to selectively bond sand within a build platform. This production process is similar to others in the design of 3D geometries as the printing itself resembles that of an inkjet printer. The system works with the injection of a sand and epoxy resin bond that combine together in layers of 5â&#x20AC;&#x201C;10 mm and do not require the use of additional structures to support the printed object. The machine has an aluminum structure of 6 by 7.5 by 7.5 m that creates a gantry crane construction system. The possibilities of fabrication are therefore reduced to an area of 6 by 6 m with a height that theoretically

is limitless, though determined by the selfsupporting characteristics of the structure. The geometrical data from the design project is verified by finite element software, and if necessary, optimized for production. As in desktop 3D printers, a STL file is transferred to a computer that manages the machine and can begin the layer printing process. A second patent (Dini, 2010) was then registered, moving from epoxy resins, which was creating maintenance problems because it was sticking to anything, including the machine itself, to inorganic binders, which operate through chemical reaction, to bind sand into synthetic stone material. This was a significant shift for the potential of the process, moving away from high cost, problematic and toxic process toward a more environmental and cheaper fabrication, thanks to the new feedstock materials: sand and oxides, and chlorides derived from seawater.

figure 3.16 The innovative technique D-Shape developed by Enrico Dini utilizes inorganic binders to stick sand particles together into a homogeneous synthetic mass. The technology has been developed for the needs of large-scale printing and the application in the construction sector

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The significant innovation by the D-Shape system is in formulating specific materials that are suitable for the needs of large-scale printing and the application in the construction sector. The high curing periods are achieved through spraying the material using three hundred nozzles. The sand is deposited in layers, while a second spray adds a fluid component that infiltrates within the granular material, and through a catalytic reaction, forms a homogeneous mass. Enrico Diniâ&#x20AC;&#x2122;s printing technique has the great advantage of providing support for overhanging geometries, as sand is selectively transformed to stone within a bed of untouched sand, allowing freeform 3D geometries to be produced. Limitations in this technology are today the strength of materials and printing resolution of approximately 5dpi (20mm in the X and Y axis and 5 mm in the Z axis). (Dini, 2010) The D-shape process has since now been tested on architectural scale in two applications, Radiolaria, a 10 meters tall sculptural pavillion designed by Andrea Morgante, and Villa Roccia Project. This projects commenced in 2009 as a

design for a newspaper article about D-Shape by James Gardiner. The design inspiration for the design is the rock formation characteristic of the project area, Sardinia, from the long tradition of rock houses of the region but aligned to the design practices of Gaudi, through seeking to understand and respond. to forces operating on the building, designing to enable production and also attempting to synthesise a relationship between man, technology and nature. The principal goal for the Villa Roccia was to create an architecture able to take advantage of the opportunities inherent in the D-Shape printing technique, through a responsive design which fit solution to a range of inputs, such as structural load, thermal comfort requirements or sun-shading. Due to size restriction of the machine, the design had to be conceived as an assembly of different elements. Taking bones as a structural reference, Gardiner envisioned post-tensioned rods inside the printed structure, to allow it to resist both to compression and tension. In the end just to parts over the entire design has been prototyped, still quite far from having

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a fully functional behaviour and aspect. The first is the Roccia Column, which has been printed off-site in 14 different pieces, each approximately 250 mm in height. Internal conduits has been integrated for post-tensioned steel cable reinforcement. The second project is the Roccia Assembly, which represents an area of the Villa. It has been designed and developed with parametric softwares, trying to balance between the original concept of rock erosion and the idea of performance optimization. In particular, TopOpt software has been used in the attempt of using Topological Optimization strategies for structural optimization, and

then through Rhino and Grasshopper joints and details has been parametrically added to the design. Unfortunately, different reasons contributed to the not fabricating of the Villa apart from one cutaway section, printed in four pieces. These projects highlight some interesting potentials of the technology, from the possibility of creating very complex shapes and to drastically optimize them to the closeness between design and fabrication. Parallelly many downsides are still limiting the technology at the moment, from the material strength to the printing definition.

figure 3.17 Left: Dimensional check of a series of sections of the Villa Roccia project. Right: Detailed digital model of one of the modules of the project. It comprises openings for pipes and post-tensioned rods, a joinery and tagging system of each piece

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3.4.3 CONTOUR CRAFTING | BEHROKH KHOSHNEVIS Los Angeles, 1998 A different approach to face the challenge of building a 3D printed architecture have been addressed by the Contour crafting experimental project, being developed since 1998 by Professor Behrokh Khoshnevis, director of the Center for Rapid Automated Fabrication Technologies (CRAFT) at the University of Southern California (USC) in Los Angeles. This system is recognized as a milestone in the attempt to transfer rapid production technology to the construction scale and offers a solution to the manufacturing of an entire structure in a single day by utilizing direct layer production that avoids extended installation times and reduces production costs by 75%. The technology is defined as a hybrid automated fabrication technique that is combining an extrusion process that is forming the object surfaces and an injection filling process to build the object core. The extrusion nozzle is equipped with a top and side trowel

which collaborate to create a smooth outer and top surface of each layer. Additionally, the side trowel could be deflected in order to shape a non-orthogonal surfaces, or at the same time, allow for thicker material deposition while maintaining a smooth surface finish. (Khoshnevis, 2014). A great advantage of this process is the possibility for a thick layer deposition, which in most processes is physically impossible, like in the cases of using a laser or adhesive liquids which cannot penetrate deep enough into the powder in order to solidify it. The thicker material deposition cuts the production time significantly, which is an essential issue for large-scale additive manufacturing. A wide choice of semi-fluid materials could be used, such as polymers, ceramics, composite wood materials, mortar, cement, concrete and other materials, that once deposited by a nozzle are able to quickly solidify and resist pressure from the weight of the structure itself. The

figure 3.18 Contour crafting is an experimental project developed by professor Behrokh Khoshnevis, that utilizes thick layer deposition of semi-fluid materials which reduces production time significantly

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forms created through this technique are selfsupporting during the fabrication process, and therefore additional structure is not necessary thanks to the quick curing times, which can be controlled by chemical additives. Currently, the Contour Crafting technology can build a 185 m2 house with all utilities for electrical and plumbing systems in less than 24 h.

Based on these characteristics, the system presents a notable advantage in respect to other construction methods, especially in terms of production costs (reduction of manual labor and materials), environmental advantages (given the absence of waste materials) and quicker manufacturing times considering the lack of temporary supports.

figure 3.19 Left: The system offers a solution to the manufacturing of an entire structure in a single day by utilizing direct layer production. Right: The hybrid automated fabrication technique combines extrusion process for printing the objectâ&#x20AC;&#x2122;s surfaces and an injection filling process for the core.

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3.4.4 CONCRETE PRINTING | LOUGHBOROUGH UNIVERSITY Loughborough, 2006 A similar technique for a different goal has been under development at the Additive Manufacturing Research Group (AMRG) at Loughborough University in the United Kingdom since 2004, within the Wolfen School of Mechanical and Manufacturing Engineering. Under the leadership of Rupert Soar and Richard Buswell, the Concrete Printing project was first conceived under the name “Freeform Construction”, with the assembly of the first machine starting in 2006. The opportunities for re-design of complex assemblies into integrated panels is the main area in which the research team has focussed, rejecting the idea of printing a monolithic structure for the entire building.First attempts in the developing such a field has been the ‘homeostatic wall and later the “Wonderwall concept” (Buswell et al., 2007). These concept designs focus on adding performance and functionality to walls, while reducing the number of materials and construction trades

required. Additional value added functions include optimisation of structural, acoustic, thermal and ventilation properties. Although construction performance based design research has continued for many years within the AMRG such design strategies were not tested as part of the recent ‘Freeform wall’ prototype (De Kestelier and Buswell, 2009). Fabrication with the Concrete Printing machine works on the basis of selective deposition of a paste material through an extrusion nozzle, similarly to Contour Crafting project. The major difference between Contour Crafting and Concrete Printing is in the nozzle: the latter is designed to have the capacity to vary its resolution to allow the deposition of both bulk materials and fine detail within the same process. (Buswell et al., 2007) With a build volume of 2m x 2.5m x 5m the Concrete Printing machine is designed for the fabrication of panels and large building components rather than whole buildings, with

figure 3.20 The Concrete Printing project investigates the possibilities to use selective deposition techniques to re-design complex assemblies into integrated panel systems rather than printing monolithic structures

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added value, functionality and capabilities over traditional construction techniques. The materials used to date by the Concrete Printing team have included cement basedmortars and gypsum materials with the use of commercially available binders for transforming the paste to solid, these materials are deposited in layers of between 6-9mm in thickness. The team is working toward the integration of support material that would

allow for the creation of overhangs and true 3D freeform geometry. (Le et al., 2011) The majority of test pieces examples demonstrated using the Concrete Printing technique, as much as Contour Crafting, have been to date 2.5D geometries, rather than real 3D freeform elements, which are supposed one of the main advantages of additive fabrication processes.

figure 3.21 Left: The concept design focuses on adding performance and functionality to walls such as optimisation of structural, acoustic, thermal and ventilation properties. Right: The technology is based on selective deposition of paste material through an extrusion nozzle.

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3.4.5 3D PRINTED HOMES | WINSUN DESIGN ENGINEERING CO. Shanghai, 2014 Although Contour Crafting and Loughborough University have done the first steps into concrete 3D printing years ago, in 2014 the Chinese company WinSun Design Engineering Co. reached the goal of completing a concrete 3D printed building. The idea comes from the need of China to give housing to the immense population continuously growing in the country, creating spread problems of overpopulation. (Wang 2014) The massive 32m by 10m by 6m machine sprayed a special mixture derived from cement and construction waste to build the basic components of the house, layer by layer. (Balinski, 2014) Each building with a size of approximately 195 m2, they are built with recycled materials, allowing for a minimal budget realization, with a cost of less than $5,000 a unit. The project is still far from being competitive

in a design perspective, but itâ&#x20AC;&#x2122;s a clear demonstrations of the economical advantages additive manufacturing could bring to the building construction field and the fast development and spreading of the technology around the world. In the first days of 2015, WinSun revealed two apparently extraordinary examples of 3D printed constructions: they have built the highest 3D printed building, a 5-storey residential house and the worldâ&#x20AC;&#x2122;s first 3D printed villa. The villa measures 1,100 square meters and even comes complete with internal and external decorations. According to Ma Yi He, CEO of WinSun, waste from recycling construction and mine rest produces a lot of carbon emissions, but with 3D printing, the company has turned that waste into brand new building materials. He also affirms that this process also means that construction workers are at less risk of coming into contact with hazardous materials or work

figure 3.22 Chinese company WinSun Design Engineering Co. reached the goal of completing the first concrete 3D printed building utilizing a massive 32 by 10 by 6 m machine which sprays a special mixture of cement and construction waste

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environments. WinSun estimates that their 3D printing technology can allow for savings between 30 and 60% of building materials and production times by 50 to even 70% reduced, while decreasing labor costs by 50 up to even 80 %. In their vision, future applications include 3D printed bridges or tall office buildings that can be built right on site. The premises seem particularly appealing, but reality is quite different. In the first instance, not the whole building has been 3D printed, but just part of the walls have been produce with WinSun new additive machines, whereas internal partitions, details and especially every horizontal elements has been produced with traditional techniques. Apart from the company ideas, FDM with cement still presents several problems: cement

takes a while to cure, and using a faster curing cement is problematic because the nozzle becomes jammed. Thus extruding layers outside a fraction of the width of the previous layer means that the material will begin to droop and creep before it solidifies. Although benefits of such a project can be already useful in emergencies situations, supplying fast and cheap shelters in case of natural disasters or overpopulation issues, as big and tall as WinSun buildings are, none of them extrude anything appealing or beautiful. They are straight, flat and completely plain. Once finished, the only indication that they were 3D Printed would be the finger-thick layer lines. Overhangs and complex forms are nearly impossible and represent a serious limitation of WinSun technology.

figure 3.23 Left: The company has estimated savings between 30 and 60% of building materials and production time reduced up to 70% compared to traditional construction methods. Right: One of the main limitations is the impossibility to fabricate complex and customized forms.

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3.5 MOLDINGS The following examples are focused on the integration of additive manufacturing more on the construction process than on the final architecture itself. In particular both Philippe

Morel and Gramazio and Kohler focuses on the fabrication of molds for concrete casting, with two distinct approaches.

3.5.1 CONCRETE CASTING | PHILIPPE MOREL Paris, 2014 Advances in the science of making concrete have led to a new class of cement composites called ultra-high performance concrete, or UHPC. The durability of UHPC makes it an ideal material for use in solutions as critical as highway infrastructure repair and replacement. While it has been around for nearly 15 years, itâ&#x20AC;&#x2122;s only now finding acceptance among architects. Additive manufacturing constantly opens up new application fields in architecture. In the beginning of 2014 architect Philippe Morel from Studio EZCT Architecture & Design

Research in Paris revealed his project of printed sand molds to be used in combination with the ultra high-strength concrete. The research activities of the EZCT focus on the search for lighter and filigree concrete structures that will provide a completely new level of design freedom in architecture in the future. Using the example of the UHPC exhibit, seen at an architecture trade fair in the FRAC Centre in OrlĂŠans until the end of March 2014, thanks to Voxeljet sand printers, a total of 130 sand mold

figure 3.24 Concrete casting is a project developed by Philippe Morel for fabricating sand molds with Voxeljet sand printers to be used in combination with ultra high-performance concrete (UHPC).

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halves for the concrete cast has been produced. After printing, the inside and outside of the various halves were infiltrated with epoxy resin and were subsequently glued together in order to achieve a very fine concrete structure. This process was followed by casting using ultrahigh performance concrete, and the assembly of the individual parts. Philippe Morel only partially removed the sand molds from the part to demonstrate how

the complex UHPC structure was created. The architect believes that the direct 3D printing of parts made of ultra-high performance concrete and bypassing the use of sand molds will be the only alternative to this production method in the future. To turn this vision into reality, Voxeljetâ&#x20AC;&#x2122;s development departments have already been studying the 3D printing of concrete materials for some time. (Voxeljet, 2014)

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3.5.2 MESH-MOULD | GRAMAZIO KOHLER RESEARCH, ETH Zurich, 2012-2014 A different research line has been followed by the ETH Zurich research unit lead by Gramazio and Kohler in the project Mesh-Mould, which addresses the 1:1 construction aspects of loadbearing structures. Considering the use of standard industrial robots with its limited payload capacities, however with a high capacity for precise spatial coordination, an optimal use of the machine requires construction processes with minimal mass transfer and a high degree of geometric definition. (Gramazio and Kolher, 2014) Afterwards, in collaboration with Sika Technology AG as an industry partner and expert in cementitious materials, the fabrication of formwork for material efficient , thus geometrix complex concrete elements constitutes the focus on their investigation: Mesh-Mould project combines formwork and reinforcement into one single robotically fabricate construction system.

The research decision to concentrate on the fabrication of formworks lead to the technology known as ‘leaking formwork’, where concrete is poured into a corrugated formwork that is built up from perforated flat plastic panels and enables the erection of straight and single curved walls. The concrete then bulge through the holes covering the formwork, with a subsequent manual trowelling of the surfaces, creating the final smooth concrete surface. Gramazio and Kohler implemented this technique through the use of extruded polymers, precisely controlled by the robot, in order to create the required meshes and liberate the formwork from geometric constraints. The use of thermoplastic polymers, such as used in conventional 3D printers, allows precise control over material’s hardening behaviour. (Gramazio and Kolher, 2014) The shift from layer-based material deposition to spatial extrusion has several

figure 3.25 Mesh-Mould is a project developed by Gramazio & Kohler research unit in ETH Zurich and addresses the 1:1 construction aspects of loadbearing structures. Mesh-Mould combines formwork and reinforcement into one single robotically fabricated construction system.

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noteworthy implications, such as the reduction of fabrication time, making the process feasible for application in construction at the large scale. A study of the forces that act on the structure allows to design a variable-density mesh, improving strength and reducing material use. This applies for the static case after concrete has cured, but even for dynamic loading during the concrete pouring process itself. Moreover, the forces-driven distribution of the structure has the potential for co-extruding a strong filament such as carbon, glass, bamboo or basalt, enabling the structural activation of the mesh, making it working for high-tensile forces and suitable for the replacement of the conventional steel reinforcement. (Gramazio and Kolher, 2014) Simultaneously the robotic freeform meshes fabrication allows for the integration of cavities for lighter porous structures, or even to generate advanced material effects, for example by

keeping the concrete from reaching all the parts of the mesh. Such possibilities could not be achieved by means of conventional mouldbased formwork systems. Mould-Mesh project envisions also the scalability of the process, by parallelisation of different working robots, reducing time and number of separate tasks, thus risks on the building site. As the robots directly extrude the reinforcing formwork in-situ, several of these crafts and professions involved can be folded into one, allowing a higher product complexity while simplifying the process itself. The unification of the two conventionally separate requirements of concrete â&#x20AC;&#x201C; the reinforcement and the formwork â&#x20AC;&#x201C; into one single robotic fabrication process, can produce an additive and waste-free, material-efficient and geometrically unconstrained method of fabricating complex non-standard concrete constructions (Hack and Lauer, 2014).

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3.6 THE DIFFERENT DIMENSIONS OF 3D PRINTING IN ARCHITECTURE Different materials, different printing processes, different applications in architecture: from the overview of the case studies it is evident that a vast range of approaches has been considered and tested. Which is the relation between technology and application? Is there an approach which best capitalise on additive manufacturing potentials? From the examples studied is evident how the final output is often strictly limited by the technology, not only in dimension, but also as far as material is concerned. For instance, James Gardiner and Enrico Dini collaboration on Villa Roccia project is highlighting how the machines influence the final result: 6x6x6 meters are the maximum dimensions of the printed elements, and the sand material together with the binding process does not yet have such performances that allow for an end-use project. However, it is

not immediate to find a comprehensive pattern of correlation between approach and choice of technology used. It is noticeable that SLS technology has been adopted in projects which required good material performances, high precision but a small scale of application: this is the case of joints, where a structural integrity coupled with a good precision is required. On the other side projects that envision a future of 3D printed houses, such as WinSun Designâ&#x20AC;&#x2122;s buildings or Freeform Construction research, take advantage of fast and quite rough printers which use a traditional building material such as cement, trying to implement the technology for their purpose. It is interesting the case of Digital Grotesque by Hensmeyer and Dillerburger, which aim is to demonstrate the potential and precision of sand-printing technology and 3D printing fabrication in general, that

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allows otherwise nearly-impossible designs and details. The architects idea seems a good approach towards an additive manufacturing technology that is everything but fully developed: envisioning a possible future of 3D printed buildings, taking advantage of the most proper technology to show the upper hands of a printed architecture, leaving all the downsides apart for a moment, confident in the drastic technology development in act in these years (Hansmeyer, Dillerburger, 2013). As already expressed analysing different additive techniques, materials are a fundamental aspect in the use of 3D printing. Therefore, the study of material solutions is in most of the projects an active part of the research. Three distinct approaches has been explored: in some projects existing materials for 3D printing have been studied and used; this is the case of Digital Grotesque and of the two plastic pavilions. Differently, in other projects materials already used in additive fabrication has been modified,

implemented and adapted to best suit the project and the architectural scale, such as the customized sand conceived by Rael and San Fratello for the fabrication of the Quake Column or the reinforced plastic developed by DUS Architect for the Canal House in Amsterdam. The last approach is the attempt of developing new materials for additive fabrication in the attempt of matching traditional manufacturing ones; an example are the cements studied by the Loughborough University or by the Contour Crafting project team. This vast set of perspectives brings out questions about which is the most proper combination of technology, material and application towards the use of 3D printing in architecture. Nevertheless, it is quite problematic to identify a unique approach as the right one to use additive manufacturing in constructions. The continuous and fast development of the technology in act could bring to new and unexpected results for a determined

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approach which at the moment may seem not very promising, such as improvements in the concrete printing process, at the moment rough and limited, might be a revolution for constructions. In general, we can say that intrinsic properties of 3D printing, such as freedom in form complexity and design customization, suggest

the use of additive technology for highly variable parts or designs otherwise impossible to be fabricated with traditional manufacturing processes: this approach would allow to capitalise on potentials of the technology and to stimulate new ideas for architects and a new language in design.

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REFERENCES Arup (2014) Construction steelwork makes its 3D printing premiere. http://www.arup.com/News/2014_06_June/05_June_Construction_steelwork_makes_3D_ printing_premiere. Accessed 21 August 2014. Balinski B. (2014) Chinese company 3D prints 10 houses in a day from recycled material. In: Architecture & Design, Cirrus Media. http://www.architectureanddesign.com.au/news/chinese-company-3d-prints-10-houses-in-aday-from Accessed on 25 May 2014 Buswell R., Soar C., Gibb A., Thorpe T. (2007) Freeform construction: Mega-Scale Rapid Manufacturing for Construction. Automation in construction, 16 (2), pp. 224-231. Elsevier De Kestelier, X and Buswell, R (2009) A digital design environment for large-scale rapid manufacturing, ACADIA 09: reForm: Building a Better Tomorrow - Proceedings of the 29th Annual Conference of the Association for Computer Aided Design in Architecture, pp.201-208. Dini E. (2010) What is D-shape. http://www.d-shape.com/cose.htm Accessed 6 June 2014 DUS Architect (2014) 3D Print Canal House. http://3dprintcanalhouse.com/. Accessed 21 August 2014.

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Gramazio F., Kohler M. (2014) Made by Robots: Challenging Architecture at a Larger Scale. vol. 84, issue 3, pp. 44-53. John Wiley & Sons, London. Le, T.T., Austin, S.A., Lim, S., Buswell, R.A., Gibb, A.G.F. and Thorpe, A. (2011) High-performance printing concrete for freeform building components, fib Symposium Prague 2011, Concrete engineering for excellence and efficiency. Hack N., Lauer V. (2014) MeshMould. Robotically Fabricated Spatial Meshes as Reinforced Concrete Formwork. In: Gramazio F., Kohler M. (2014) Made by Robots: Challenging Architecture at a Larger Scale. vol. 84, issue 3, pp. 44-53. John Wiley & Sons, London. Hansmeyer, M., Dillenburger, B. (2013) Towards a Micro-tectonic in Architecture. In Serbian Architectural Journal. Khoshnevis, B. (2014) Contour Crafting. http://www.contourcrafting.org/. Accessed 12 October 2014. Naboni, R., Paoletti, I. (2014) Advanced Customization in Architectural Design and Construction. Springer Verlag. Peters, B. (2012) Building bytes. 3D printed bricks. http://buildingbytes.info/. Accessed 18 October 2014. Sabin J., Miller M., Cassab N., Lucia A. (2014) PolyBrick: Variegated Additive Ceramic

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Component Manufacturing (ACCM). 3D Printing. vol. 1, No.2, DOI: 10.1089/3dp.2014.001. Mary Ann Liebert, INC. Smith | Allen (2013) Echoviren. In: ArchDaily. http://www.archdaily.com/419306/echoviren-smith-allen/ Accessed 14 December 2014. Van der Kley M. (2014) Project Egg. http://projectegg.org/project-egg/. Accessed 11 January 2015. Voxeljet (2014) Casting of Concrete. http://www.voxeljet.de/en/case-studies/case-studies/casting-of-concrete/. Accessed 7 October 2014. Wang L (2014) Chinese company assembles 10 3D-printed concrete houses in a day for less than $5,000 each. In: Inhabitat. http://inhabitat.com/chinese-company-assembles-ten-3d-printed-concrete-houses-in-oneday-for-less-than-5000-each/winsun-3d-printed-houses-7/, Accessed 30 May 2014

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“In Her [nature’s] inventions nothing is lacking, and nothing is superfluous.” Leonardo da Vinci

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4.1 MATERIAL IMPLICATIONS IN ARCHITECTURAL DESIGN Building construction strategies in terms of materials appear to be mostly wasteful, with a great dispersion of resources and energy. The construction industry has always been dependent on discrete solutions for distinct functions. Building skins can be considered a substantial case of this issue. Glass and steel retain seriously different structural and environmental properties which demand for different performance requirements. Diversity corresponds to a huge increase in costs and production complexity, and it is typically mass-produced, not customised. Can additive manufacturing technology open up a era of new possibilities for architects to think, but also to design and produce definitely optimized and fully customized buildings? The study of architectural design and fabrication methods have historically evolved

together. From adobe brick construction dating before 7500 B.C. to today’s additive manufacturing technologies, fabrication techniques have developed alongside design strategies and architectural styles. New design expressions have advanced innovation in construction techniques, while new fabrication technologies have inspired designers and architects to further push the envelope of design. This historical perspective allows us to distinguish between fabrication technologies that merely make the construction process more efficient, and others that fundamentally transform our way of thinking about building and buildings (Oxman et al., 2013). In the beginning of his history, man was taking advantage of natural shelters, living in caverns, without having any notion of “construction”. Human development brought man to build,

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using natural materials, such as wood and rocks, his own houses. To improve quality and performances of the building, man started creating specific materials for construction by mixing natural resources, such as for clay, and then, later, cements. Lately metal alloys, polymers and plastic materials have been developed, widening the range of opportunities for architects and engineers to improve design and performances of buildings. The evolution

of architectural design has always been coupled with a technological development of fabrication and building processes but also by an evolution in materials engineering for constructions. Design is generally intended as the shaping of material at the macroscopic scale through form. Its evolution has been influenced directly by the advancement of our methods of form representation. Computation has provided the most radical shift in our methods of prescribing

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volume, providing a set of tools that abstracts form to a dimensionless and absolute state. The complexity of representation is no longer defining what can be rendered, but rather it is our ability to understand and take advantage from the language of construction, to translate those inputs in the representation and then render the representation with the least tolerance (Oxman, 2011). If material is considered through a structural hierarchy, the act of

designing synthetic material is enforcing control over these structures at various dimensional scales to exhibit properties of our choosing. From the last decade, a new approach towards design, known as material â&#x20AC;&#x2DC;material-orientedâ&#x20AC;&#x2122;, is focusing on studying materials properties and natural precedents, to inform design and embed those notions, such as mechanical behaviors of a material, in order to improve performances. This approach take advantage of computational

figure 4.1 ICD/ITKE Research Pavilion 2010 demonstrates an alternative approach to computational design: the generation of form is directly driven and informed by physical behavior and material characteristics

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design tools to make digital analysis and exploit the results in such a way that form is directly driven and informed by physical behavior and material characteristics. Any material construct can be considered as resulting from a system of internal and external pressures and constraints, which determine its physical form. In the physical world material form is always inseparably connected to external forces, in the traditional design process form and force are usually treated as separate entities, as they are divided into processes of geometric form generation and subsequent simulation based on specific material properties. As a proof of concept, for the construction of the ICD/ITKE Research Pavilion 2010, developed by Achim Menges and his researchers at ICD in Stuttgart, Germany, the design team researched on the properties of plywood, which resulted in a bending-active structure made entirely of extremely thin plywood layers, which computationally embed the anisotropic fibrous composition of wood into design strategy and take advantage of its elasticity along the fibers to fabricate and construct such a lightweight

structure (Menges, 2012). Additive-based methods of construction guarantee perhaps the most direct route of physically rendering forms shaped by digital tools (Duro-Royo et.al., 2014). A great asset of 3D printing is that it offers the possibility to control every single voxel of the object produced directly from the digital model. Indeed thereâ&#x20AC;&#x2122;s a direct correspondence between digital 3D model and physical object, since the informations for the machines are directly extracted from the digital environment. The minimal unit of the process can be identified as the voxel, the three-dimensional equivalent of the pixel. A voxel represents a single sample, or data point, on a regularly spaced, three-dimensional grid, corresponding to the overall volume of the digital model. This data point can consist of a single piece of data, such as its dimension, or multiple pieces of data, such as colours, or different material properties. Additive fabrication allows to directly transfer those data into physics. The voxel dimension thus corresponds to the resolution of the machine, and sets the final definition of the object. This straightforward link

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between digital and physical, between bits and atoms, enables a more complex and outright control over the fabricated objects. Hence, this set of technologies has the potential to go two step further than traditional methods. With such a fabrication process it is not only possible to generate every kind of complex shape without any additional production complication or costs increase, but it is also viable to freely organize internal material distribution over the volume, according to desired parameters. This allows for complex internal geometries but also for 3D grading of different materials over the volume.

While in the past the predominant optimization technique was to design form as a function of material, graded building components might offer an entirely new approach: the design of material as a function of form (Heinz, 2011). It is therefore possible to identify different optimization approaches, implying mutations at varying scales: those which imply a modification in the external shape of the analysed object or system, and those which entail an heterogeneity or anisotropy across the volume, under the form of geometrical variation or material properties mutation.

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4.2 MACRO-SCALE MATERIAL ORGANIZATION: TOPOLOGY OPTIMIZATION Topological optimization is a mathematical approach that aims at optimizing material layout within a given design space, for a given set of loads and boundary conditions such that the resulting layout meets a prescribed set of performance targets. Topology optimization software systematically analyzes the stresses on these shapes and then removes the most superfluous material from the design. This process is repeated over and over by the software until the target amount of material is reached, and by the end the computer design leaves only a skeletal structure. The advantage of parts made with topology optimization is therefore that the same strength characteristics can be created with less material, and this yields a greater strength to weight ratio, an important property across most industries, from automotive, to aerospace, but also architecture

and building construction. As a practical example, structural rib elements in an Airbus wing designed with topology optimization saved over 500kg in structural weight, which translates to significant cost savings. (Jaffe, 2013) If it is such a valuable process why has it not been implemented in the field of architecture to a much higher degree? In last decades architects made an important step towards recognizing the relationship of topological optimization and nature through simple studies of structural elements commonly used in traditional building methods. They have discovered through the use of advanced software programs that living structures found in nature are inherently optimized to make use of the least amount of material for â&#x20AC;&#x153;the given design space, set of loads, boundary conditionsâ&#x20AC;? and function. The computing power to run topology optimization

figure 4.2 Generico Chair designed by Marco Hemmerling reveals potential for an ideal 3D-printing-technology application as it allows for an optimal distribution of materials

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software became available in the 1990â&#x20AC;&#x2122;s, but the technology did not spared as imagined by its creators. Reflecting on its limited success twenty years ago today, it is worth noting that the real difficulty wasnâ&#x20AC;&#x2122;t in designing parts, but in producing them. Three-dimensional designs created in such a way were often highly irregular with strange voids and curved interior surfaces, making them all but impossible to machine or cast using traditional manufacturing methods (On3DPrinting, 2014).

However, with the increasing development of additive manufacturing makes producing highly complex building elements as easy as producing straight, right-angled beams. Topology optimization can be now increasingly adopted and coupled with additive processes to capitalize on both design, analysis and fabrication innovations. Traditionally, in the design of the topology of a structure we are interested in the determination of the optimal placement of a given isotropic

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material in space, i.e., we should determine which points of space should be material points and which points should remain void, without material. We may think of the geometric representation of a structure as similar to a

black-white rendering of an image. In discrete form this then corresponds to a black-white raster representation of the geometry, with voxels given by the finite element discretization.

figure 4.3 The image shows the stress lines of a bone structure that is inherently optimized to reach maximum performance with minimal resources

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4.3 MICRO-SCALE MATERIAL ORGANIZATION Additive processes has the potential to fabricate volume optimized until the scale of the voxel, almost without restrictions in terms of discretization. Moreover this fabrication techniques may open to a different approach towards the results of topological optimization: in fact with the increasing advancement in additive manufacturing technologies, it is more and more accessible the possibility to vary properties, such as stiffness, opacity and so on, to printed material, or even shift between different materials, for instance plastic together with metal alloys. This variation at the micro-scale may results in a gradual variation of the geometry, of itâ&#x20AC;&#x2122;s thickness or even in the properties along the volume, switching from a 0-1 design optimization to a gradientbased domain optimization, with intermediate densities between white and black, the full

and void areas usually taken into consideration during topology optimization analysis. Until today, the research around anisotropy and heterogeneity as a generative means to create form is still rather limited and unexplored, in the digital computational modelling environment and therefore in possible productions and applications. The implications of controlling material heterogeneity at building scales from a design perspective are immense, especially in terms of efficiencies and effectiveness of both products and processes and their capacity to respond to external local requirements and pressures. But moving from substance variation to formal expression and from material to construction scale seems a long and difficult process. Additive-based fabrication might be the suitable solution for the production of such complex, non-standard micro-structures.

figure 4.4 Normal human vertebral bone structure showing micro-scale material organization

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4.3.1 HETEROGENEITY Comparing manmade fabricated materials to many natural materials, particularly in the plant world, the latter often mechanically outperform some of the most common materials used by engineers and architects (Oxman, 2010 b). What are the aspects that make natural materials so effective? Niklas, in his Plant Biomechanics: An Engineering Approach to Plant Form and Function, determines that organisms are guided by the laws of physics and chemistry and as such they have evolved and adapted to mechanical forces in a manner consistent with the limits set by the mechanical properties of their materials (Niklas, 1992). Moreover, in the plant world particularly it is often the case

that material properties influence the plantâ&#x20AC;&#x2122;s mechanical behavior. Niklas demonstrates, for instance, that the nutshell of the macadamia is as hard as annealed, commercial grade aluminum, resists twice the force necessary to fracture metals of various types, and is stronger than silicate glasses, concrete, porcelain, and domestic brick. Hence the mechanical behavior of any single biological material is defined by multiple properties, not all of which can be maximized. Each material is used according to its particular qualities and the types and magnitudes of the mechanical forces it must sustain (Oxman, 2010 b). In The Mechanical Properties of Natural

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Materials, Gibson explores various classes of natural materials, analysing the relation between their composite and cellular microstructures and their exceptionally high values of mechanical performance (Gibson, 1995). The function of these natural materials exploits their exceptional structural properties: woods and palms resist bending and buckling, silk stores elastic strain energy, muscle stores and releases elastic strain energy during locomotion, and so on. When considering beams and plates of a given stiffness or strength, or columns of a given buckling resistance, woods, palms and bamboo are among the most efficient materials available:

such relations have significant implications for the design of mechanically efficient engineering materials (Gibson, 1995). Common to all these examples are the exceptional properties of natural materials arising mainly through novel microstructures for efficient engineering materials. Hence natureâ&#x20AC;&#x2122;s structures are not much unique for their material properties but more for their arrangement within the natural composites, which give rise to such a vast range of properties. As Neri Oxman affirms in her doctorate thesis, we may affirm that material structure is an important design property of natural structures, as well as a significant body of design knowledge (Oxman, 2010 a).

figure 4.5 Functionally graded concrete developed by the Institute for Lightweight Structures and Conceptual Design (ILEK) at the University of Stuttgart.

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4.3.2 ANISOTROPY Traditionally, we tend to classify materials, along with their various properties, either as structural or as functional (Stoneham and Harding, 2003). Structural materials are mainly employed for their mechanical properties, whereas functional materials have different other uses, relative to thermal, optical, electrical properties, or combinations between them. It is however quite challenging to distinguish between structural and functional materials in nature, as most biological materials such as wood can be both structural, supporting the branches of a tree, and functional, pumping water up to the leaves, with different scales for these different roles. Nature achieves such integration by varying the materialâ&#x20AC;&#x2122;s properties and introducing in it directional changes relative to their functions. This ability is termed anisotropy, which is, generally speaking, defined as directional dependency. It is expressed as a given difference in a materialâ&#x20AC;&#x2122;s

physical property (absorbance, refractive index, etc) when measured along different axes (Bar-Cohen, 2006). In design, examples vary depending on the type of property being examined and the manufacturing technology applied to manipulate material organization. Over the last decade, advancements in textile design have proved the distinctive role fibers play in the design of products and environments. Certainly, anisotropy is one of the most relevant properties for a designer operating at the heart of contemporary design culture. Its many potential interpretations as a method for controlling material organizations seem incredibly promising in an age where developments in material science impact processes and products in design (Oxman 2010, b). It may be not so visionary to consider this new realm of engineering materials a precious resource for the architect, moving from the idea of material selection to that of material design.

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4.4 VARIATIONS IN GEOMETRY In nature, shape is cheaper than material, yet material is cheap because it is effectively shaped and efficiently structured. Microstructural organization of material is a widely present characteristic in the natural environment: material is concentrated in regions of high strength and dispersed in areas where stiffness is not required. Additive manufacturing is a unique fabrication technology, yet thanks to its precious ability to allow for variation in shape without increasing production complexity and costs, it probably is the most suitable technology for a complete optimization without the need of discretization and approximation with respect to the digitally designed 3D model, partially closing the gap between natural and artificial realms in terms of performance-driven fabrication. The opportunity of nature to gradually change performances by way of locally optimizing regions of varied external requirements, similarly to bones ability to

remodel under altering mechanical loads or the wood’s capacity to modify its shape by way of containing moisture is facilitated fundamentally by its ability to simultaneously model, simulate and fabricate material structures, it’s creating intricate and peromative systems (Oxman, 2011). Such a dynamic and iterative model can not be directly implemented in the built environment, but it could be integrated during the design process in order to iteratively find the optimal solution that best fulfill multiple performative requirements. Geometrical variation inside a building structural element has been investigated by the german researcher Daniel Büning. His research started in 2011 trying to understand the possibilities of applying additive manufacturing in the construction field and how to enhance construction processes through 3D printing in combination with different digital simulation processes. Büning’s idea is to look at natural

figure 4.6 Natural column project designed by Daniel Buning is an architectural free-form column with an internal three-dimensionally graded heterogeneous microstructure, derived through a structural simulation process

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elements such as bones, which have the exterior hull shape and an internal hull inhomogeneous microstructure with the intent to emulate not just the optimized freeform envelope, but also the internal logic of structural performance cavities (Daniel BĂźning in: Wheeler A., 2014). The Natural Column is one of the architectâ&#x20AC;&#x2122;s attempts to experiment onto the generation of shape through a structural optimization process, coupled with a research on the inner microstructure, further optimized according to structural needs. This means that in an iterative computational process material is taken away in areas of the object, where it is structurally not needed, and at the same time this procedure saves weight and material, which is what makes it interesting from a sustainability perspective. The interior organization results a three-dimensionally graded heterogeneous area characterising an object with high structural performance to material saving ratio. The internal structure is made of X shaped quadrangular cells, due to the structural capacity of the shape, further implemented into the topology optimization process. On top

of the optimization he created a feedback loop so that the numeric values contained in each structural cell for local stiffness, density and deflection are extracted and fed back into the process, to control radii and material usage of the substructure. The architect is thus facing a multiple optimization problem, which he solved by creating a periodic and stacked internal structure, varying thickness diameter of each quadrangular cell with respect to the locally detected stress value. His approach, as the architect himself says, is still far from natural non-periodic configuration (Daniel BĂźning in: Wheeler A., 2014). The Natural Column is printed in blocks by the huge Voxeljet printer, through an SLS process. This research outlines a novel digital workflow for the design, simulation and fabrication of large-scale architectural elements that are additively manufactured. Moreover the Natural Column project highlights the advantages of additive manufacturing by triggering its real potentials (for the creation of complex internal structures within an object) and enhance industrial sequences and design processes to

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create more digitally informed, sophisticated and cost efficient products (Daniel BĂźning in: Wheeler A., 2014). It is thus possible, for example, to think about a wall consisting purely of one material, such as concrete, which fulfils all of the requirements of a building envelope. This solution has different positive effects, both increasing valuable usable floor space, significantly improving the recyclability of the building component, in comparison to a typical Exterior Insulation and Finishing System (EIFS), which usually consists of dozens of different materials, definitely bonded together in such a way that make separation and recycling is almost impossible. Through the a graded transition from a dense supporting outer layer to a highly porous insulating inner layer, purely mineral-based outer wall elements can be achieved which are only a quarter of the wall thickness of comparably high-performance insulating concretes (Heinz, 2011). The insertion of a tight interdependency between form, performance and matter points to an enhanced, more sustainable and environmental-friendly manufacturing cycle.

Continuously decreasing tolerances and increasing fidelity of additive layer systems is going to create new opportunities in design and construction. Among them thereâ&#x20AC;&#x2122;s the ability to design below the macroscopic scale, resulting in the design and engineering of hybrid materials where every micron has been studied and optimized during the process (Beckett and Babu 2014). This is what Richard Beckett of the Digital Manufacturing Centre (DMC), a laboratory based in the Bartlett School Of Architecture, has been studying in last three years together with Sarat Babu of Betatype studio, trying to explores the potential of a new architecture that enclose different scalar levels, from meter to micrometre. The Interface/4 is a 1:1 scale prototype sponsored by EOS and Netfabb, part of an ongoing series of experiments trying to explore how optical variability can be achieved through localised channeling and diffracting material structures. The approach enables a high degree of flexibility in response to a site context without

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the need for the gross volume of the shape to change, but rather, the envelope can be adapted to respond through the broad range of optical and mechanical possibilities. Constructed of laser sintered nylon, the mock-up consists of over a hundred components with ten different structural geometries leading to the majority of the structure achieving a thickness of 1 mm, maintaining a structural stiffness-to-weight ratio that enables practical application within its spatial boundary. The architects designed four different levels, primary structure, secondary structure, surface and filter, to emphasize the possibilities of local variation along the surface. The entire prototype was built in a single laser sintering tank in over 4700 120Îźm layers and took five days to build the entire model and

thought for near site production. The polymers sintering process enables thou the production of materials with comparable properties to engineering-grade plastics. At the same time, the unique feature of the process produces stable structures with wall thickness as fine as 400 micrometres (Beckett and Babu, 2014). The complex modelling of surface and interior part of the project show how the challenge for additive manufacturing is not just in the underlying technology, but the improvement of design skills, in software but nevertheless in the conception of design, as a multi-scalar complex apparatus, which presents complexity and massive data flow but offer infinite new possibilities for designers (Beckett and Babu, 2014). The revolution in manufacturing is thou limited without a revolution in design processes.

figure 4.7 Interface /4 is a design developed by Richard Beckett and his team. The interface explores how optical variability can be achieved through localised channeling and diffracting material structures and is constructed of laser sintered nylon

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4.5 VARIATIONS IN MATERIAL INTRINSIC PROPERTIES The ability to strategically use and employ relationships between the spatial organizations of materials and their intrinsic properties across various scales will possibly enable the future description of material properties in terms of architectural parameters, qualities and applications. Moreover, as heterogeneity, anisotropy and multi-functionality, which are representative results of the adaptivity of the morphology, become designable, the ability to independently arrange material properties and develop structural materials with largely superior properties corresponding to their environment could be achieved (Oxman, 2010 b). For instance, by grading the interior porosity of structural building components, material properties can be precisely matched to the actual applied loads. In current architectural design fabrication does not exist a rapid

prototyping technology which allows for a continuous variation of material properties such as strength, density and elasticity as gradients across surface or volume of functional components. Such modifications can be hardly achieved as discrete changes in physical behavior by producing multiple components with different properties and distinct separation between different materials. Such a process generally result in material waste and lack of functional precision (Oxman, 2010 b). That is what Neri Oxman of Mediated Matter Group in MIT, Boston, along with her research on Material-based Design Computation method and techniques, developed the â&#x20AC;&#x153;Beastâ&#x20AC;?, a case study demonstrating the possibilities of additive manufacturing and material properties variation. A single continuous surface acting both as structure and as skin is locally modulated

figure 4.8 Beast is a prototype for a chaise lounge designed by Neri Oxman. It combines structural, environmental, and corporeal performance by adapting its thickness, pattern density, stiffness, flexibility, and translucency to load, curvature, and skin-pressured areas respectively

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to satisfy load-bearing and comfort functions respectively. Oxman and her team designed, analysed, and fabricated the chaise combining structural, environmental, and corporeal performance by adapting its thickness, pattern density, stiffness, and translucency to load, curvature, and skin-pressured areas. Different algorithms were generated corresponding to each of these potentially conflicting variables, such that stability is negotiated with a sense of comfort upon surface contact, and structural integrity with visual and sensual experience. The cellular pattern applied to the furniture is designed to increase the ratio of surface area to volume in areas optimized for a sense of comfort. Analysing anatomical structures that cause concentrated pressures, the chaise becomes softer and flexible where pressure needs to be relieved. The relative volume of each cellular cushion is locally informed by pressure data averaged with values that represent structural support and flexibility. Global and local mean curvature values inform its density, such that denser, smaller cells are organized

in areas of steep curvature, whereas larger cells are found in areas of shallow curvature. The chaiseâ&#x20AC;&#x2122;s natural relation of structural and sense datum is propagated in variable polymer composites, offering a wide range of physical properties. Through these algorithms force conditions naturally propagate functionality. Stiffer materials are positioned in surface areas under compression, and softer, more flexible materials are placed in surface areas under tension. The surface patches are printed in 3D, using a new multi-jet matrix technology which simultaneously deposits materials of different properties in correspondence to structural and skin-pressure mappings (Oxman, 2010 b). Moreover, Oxman and her team are currently exploring a novel material deposition 3D printing technology, that can offer gradation control of multiple materials within one printing process, to save weight and material quantity together with reducing energy inputs. She called such an experimental technology â&#x20AC;&#x153;Variable Property Rapid Prototypingâ&#x20AC;?, able to fabricate a continuous gradient material

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structure, potentially optimized to fit structural performances with efficient use of materials, reduction of waste and production of highly customized features. Such an approach aims at significantly reducing material and energy

waste by constructing structures with varied properties which would allow for lighter and stronger material, as well as avoiding the use of not necessary material.

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REFERENCES Bar-Cohen, Y. (2006) Biomimetics : Biologically Inspired Technologies. CRC/Taylor & Francis, Boca Raton, FL. Beckett R., Babu S. (2014) To the Micron: A New Architecture Through High-Resolution Multi-Scalar Design and Manufacturing. In: Sheil B. (2014) Architectural Design. Special Issue: High Definition: Zero Tolerance in Design and Production. vol.84, issue 1, pp. 112-115. John Wiley & Sons, Ltd., London. Duro-Royo J., Zolotovsky K., Mogas-Soldevila L., Varshney S., Oxman N., Boyce M., Ortiz C.(2014) MetaMesh: A Hierarchical Computational Model for Design and Fabrication of Biomimetic Armor Surfaces. Computer-Aided Design, Elsevier , Vol. 60, pp. 14â&#x20AC;&#x201C;27. Gibson, L. J., Shercliff, H. R. (1995) The mechanical properties of natural materials. II. microstructures for mechanical efficiency, Proceedings Lond. AR. Soc., Vol. 1, pp. 141â&#x20AC;&#x201C;162. Heinz P., Herrmann M., Sobek W. (2011) Functionally Graded Building Components. University of Stuttgart Institute for Lightweight Structures and Conceptual Design. Production procedures and fields of application for functionally graded building components in construction. Zukunft Bau, ILEK. Jaffe, B. H. (2013) Topology Optimization in Additive Manufacturing: 3D Printing Conference (Part 5). http://on3dprinting.com/2013/04/23/3d-printing-conference-5-topology-optimization/ Accessed 8 December 2014

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Menges, A. (2012) Material Computation: Higher Integration, in Architectural Design: Morphogenetic Design, Menges A. ed., Wiley, vol. 82, no. 2, pp. 14-21. Niklas, K. J. (1992) Plant biomechanics : an engineering approach to plant form and function. University of Chicago Press, Chicago. On3DPrinting (2014) Airbus Envisions a 3D Printed Future. http://on3dprinting.com/2014/04/04/airbus-describes-3d-printed-future. Accessed 12 December 2014. Oxman N. (2010) (a) Material-based Design Computation. Ph.D. thesis, MIT Oxman N. (2010) (b) Structuring Materiality: Design Fabrication of Heterogeneous Materials. In Architectural Design, Special Issue: The New Structuralism: Design, Engineering and Architectural Technologies, Oxman Rivka, Oxman Robert (eds.), vol. 80, no.4, pp. 78-85, London. Oxman N. (2011) Variable Property Rapid Prototyping. Journal of Virtual and Physical Prototyping (VPP), 6:1, 3-31 Oxman N., Laucks J., Kayser M., Tsai E., Firstenberg M. (2013) Freeform 3D Printing: toward a Sustainable Approach to Additive Manufacturing. Green Design, Materials and Manufacturing Processes published by Taylor & Francis , ISBN: 978-1-138-00046-9. Stoneham A., Harding, J. (2003) Not too big, not too small: The appropriate scale. Nature Materials, Vol. 2, No. 2, pp. 77â&#x20AC;&#x201C;83.

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Wheeler A. (2014) An Interview with Daniel BĂźning - Talking 3D Printing, Art & Architecture. 3D Printing Industry. http://3dprintingindustry.com/2014/07/13/interview-daniel-buning-talking-3d-printing-artarchitecture/. Accessed 8 January 2015.

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5.1 DESIGN ASSUMPTION After the review and acknowledgment derived from the study of the state of the art in technology and applied researches concerning additive manufacturing for architecture, from an insight on the potentials of control over material organization, and from the personal experience with producers and practitioners in the field, I will discuss my personal approach

towards the use of 3D printing in architecture. In particular, in the next paragraphs will focus on the area of application into the building and the scale of fabrication. The final aim of the project is therefore to propose an experimental application of additive manufacturing in architecture.

5.1.1 DIRECT DIGITAL MANUFACTURING Additive manufacturing has been used for years to make prototypes, visual models or mold masters but only in last decade it has been increasingly adopted as a direct manufacturing process, producing an end, ready for use, product. Research into the field is evolving towards incorporating sophisticated materials and material organization methods within the

fabrication process. Companies and research groups that are at the forefront of this research appear to be incrementally growing: MarkForged (Greg Mark, Boston) has developed a method to 3D-print carbon-fiber and tough plastic reinforced composites. Parallelly, as already presented in previous chapters, additive fabrication with metals has become possible, inspired by manual spray welding.

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Oxford Performance Materials, from South Windsor, Connecticut, has developed OXFAB, an engineering resin for SLS 3D printing with enormous mechanical strength, heat resistance and biocompatibility properties (OPM, 2014). Advances in structural material deposition empower the use of an increasing number of high-end materials with exceptional properties and make AM a possible and promising manufacturing technology that goes well beyond prototyping (Duro-Royo et al., 2014). As demonstrated in the review of case studies, many attempts have already been done to benefit from this set of techniques in architecture, with different approaches and different technological solutions. The primary advantage of a direct use of printed parts is that their fabrication is freed by constraints imposed by traditional manufacturing processes, such as injection molding or die casting. With such a technology available for use, many of the â&#x20AC;&#x153;factsâ&#x20AC;? that are taken from granted during the effort of designing, manufacturing and assembling are being altered. The application of additive processes does not imply a global replacement of traditional manufacturing, but it is more an alternative that could bring

improvements into the field of constructions. Regulations and requirements makes additive fabrication in architecture developing slower than in other sectors, economic, political and technical implications of such a change are creating frictions and delayings research upon it, since big construction companies have well established factories as well as procedures that grants them a relevant market with relevant profits. However, the enormous shift have the potential of creating a completely new ways of thinking, new processes, modified work flows and innovative procedures. A direct application of additive processes presents a radical departure that allows designers, engineers and manufacturers to do what was previously impractical or impossible. This is opening the door for new designs, new markets and new business models. It is a radical departure that affects more than design and manufacturing engineering. It has broad impact throughout the entire organization. The thesis will therefore try to study a novel approach towards the use of additive manufacturing for a direct application in architecture.

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5.1.2 ARCHITECTURAL APPLICATION: BUILDING SKIN Among the set of cases, different applications in the building has been conceived and tested, from joints to vertical structural elements to entirely 3D printed homes. The facade of a building is the interface between outside and inside, between public and private domains. The skin influences both appearance and performance, determining visual identity, character and functional effectiveness of the building. These distinct features continuously inspire new design ideas and technical developments for the architecture of tomorrow. Building envelopes must respond to multiple and increasing demands. Technical requirements are all directed at those fields relevant to human comfort within the built environment, such as visuals, acoustics and safety. Parallelly performance criteria are directed by the increasing need to reduce carbon emissions, both in construction and during the lifecycle of the architecture. Nevertheless building skins design is increasingly demanding for variation, from simple and flat facades, to

curvy and folding envelopes, from the use of integrated lighting systems to colors, textures and responsive systems. Finally, since vertical construction carries with it the design constraint of self-loading, itâ&#x20AC;&#x2122;s important that materials, in addition to being strong, should be light (Niklas, 1992). All these issues are bringing to a continuous broadening of the range of materials and production processes used and studied for building skins. Additive manufacturing technology gives the possibility to freely distribute material where needed, without increasing time and cost with the increasing geometrical complexity of the construction, thus guaranteeing great design freedom and allowing completely customized and optimized architectures. This degree of freedom given by additive manufacturing processes is a potential breakthrough in facades design, setting every design concept and idea at the same level of fabrication complexity, allowing designers to forget about costs and production limitations.

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5.1.3 ARCHITECTURAL PRINTING SCALE: THE COMPONENT Examples has been shown of the scaling-up of current technologies to try to meet size and time requirements for building construction, as well as examples which try to take advantage of existing industrial or even desktop 3D printers to create different sizes components for buildings. A great issue arises facing the use additive manufacturing to construct full-scale architecture: existing large-scale 3D printing methods can only print highly rough shapes with absence of details, while existing highresolution technologies have limited printing space, slow printing processes, most materials have weak properties for structural purposes, and generally high costs. (Hansmeyer et al., 2013) Nevertheless, existing additive processes would allow the production of highly detailed, light and transportable components, potentially capitalising on additive manufacturing great possibilities in terms of design freedom and variation. On the one side it is true that printing entire buildings might imply a faster production

process, grant also better solidity to the construction, as well as avoiding connections problems. albeit with existing constructionscale printing processes, mainly based on crane technologies, a huge, expensive and inaccurate printer would be needed. Hence, the state of the art of the technology suggests that, particularly at the moment, the most suitable solution that allow to take more advantage of it, is to work at the scale of the construction component. Shorter production process, higher detailing possibility, dimensional limits of most machines and transportation issues are the main advantages. Ideal dimensions for future developments may be modules or panels between one and three meters as maximum size. This size give more freedom of design onto the single panel, as well as reducing weak connections with respect to a smaller tiling. At the same time such a restrained dimension allow for easy transportation and maneuverability. For the

figure 5.1 The image shows a design proposal for Civil Courts of Justice building in Madrid by Zaha Hadid architects accentuating environmentally adaptive faรงade

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aforementioned reasons, along the experiments of the thesis a component-based 3D printing architecture will be envisioned. Building with the use of components imply different questions. First of all, discussing about performative envelopes, it is crucial the issue of tessellation. How to subdivide a facade in components without losing those performances implemented in the design? Tiling is necessarily all around us: it is the act of rationalizing highly complex form by breaking it up into smaller, continuous, smaller components that are geometrically congruent to their neighbors. Traditionally, in the synthetic world, tiling implies geometrical considerations traditionally defining choices, followed, afterwards, by behavioral and performance constraints and material choices (Oxman, 2009). A rationalization of the overall geometry itâ&#x20AC;&#x2122;s often entailed, mainly because of fabrication limits, but with additive manufacturing technology such limits are overtaken, thus tiling could even become a benefit more than a disadvantage. If well planned, tiled objects can be easily designed and assembled. However, a

geometric-centric view of tiling, whereby a predefined form determines the shape, size, and organization of tiles, has victimized the field of digital design. In this environment, form finding is thus restricted to the relationship between structure and geometry (and/or fabrication); it does not generally entail and incorporate the expression of material properties and behavior, as well as assembly or overall geometry considerations. Newly developed digital design tools, such as parametric and computational softwares, allows for the study and definition of a likely infinite range of possible subdivision of the facade surface. In her doctorate thesis, Oxman envisions four drivers for tessellation: curvature, assembly, performance and material (Oxman, 2010). Curvature-based tessellations are those informed by the geometrical features of the overall surface to be tiled; more generally I suggest to define it surface-based tessellation. Examples comprise the size-variation transformation of polygonal elements as a function of the type and degree of curvature: smaller polygons can be located in regions of high curvature, whereas larger cells are

figure 5.2 Arachne is a prototype design for armor by Neri Oxman. Soft and flexible materials are combined and distributed following continuous web morphology to accommodate for multiple functions such as protection, enhanced movement, flexibility and comfort

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positioned in regions of low curvature. Differently, assembly-based tessellation are defined by fabrication constraints. This is related to the dimension and geometry restrictions of production machines, as well as, in case of repetitive fabrication, in which the size of each polygon is equal to all others, the polygonal tiling would be symmetrical across all directions. In other cases, the number of discrete measurements defined by the logic of assembly informs cell size and distribution. Performance-based tessellations embed a set of performance criterias which guides the subdivision process. They can vary according to type and magnitude of mechanical loads or heat flux, but also light irradiance and wind loads. In such cases the variation of cell size and density is deriving from an analysis of the desired guiding performance (they can even be more than one), resulting though in a function of force vectors emulating magnitude and

direction of reaction forces. Finally, material-based tessellation acts assigning physical features to areas of the surface based on the analysis of stress, strain, temperature flux and other performative features. Mechanical material properties might govern form, size and density of tassels. The main difference of this approach is that it relates to the surfaces as a substance with an heterogenous composition domain. The tessellation is informed by the location of the set of elements according to mechanical behavior. Such a typology of tessellation refers to the performative approach for its guiding driver of analysis, but embedding physical properties into the model. This kind of approach must deal with both design and fabrication limitations, which restrict possibilities of materic variation into the production process, but also does not allow full integration of physical properties of materials in the digital design phase.

figure 5.3 The GEOtube Tower proposal is a scale model for a Vertical Salt Deposit Growth System for Dubai. The modelâ&#x20AC;&#x2122;s modular components were fabricated using translucent salt material developed by Emerging Objects, a subsidiary of Rael San Fratello

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5.2 FABRICATION CONTEXT Every architect has to deal with physical concept models and maquettes since the beginning of his academic career, often requiring a consistent quantity of effort and creativity to shape and render a project into physical object. Additive manufacturing in last two decades has been increasingly used for this purpose. My knowledge of this technology was limited to such an application until I started using 3D digital modelling and parametric softwares, which give the possibility to control not only the design of complex shapes, but also to discretize them and prepare files for fabrication. Additive technologies are thus among those fabrication

techniques which may take advantage of such digital tools that enable complexity, and vice versa, since often it is still difficult to give form to complex digital models via subtractive machines. Hence, in May 2014, I started investigating into the world of 3D printing, understanding soon that bibliographic research was not enough to have an exhaustive comprehension of the topic. The following paragraphs will describe my personal experience with machines, services, but also producers and practitioners in the field of additive manufacturing.

5.2.1 3D HUBS SERVICE My first direct practice with the 3D printing realm was partially indirect. I used the service 3D Hubs to print a physical model for a design

studio. 3D Hubs is the worldâ&#x20AC;&#x2122;s largest network of 3D printers, a collaborative production platform for 3D printer owners (Hubs) and makers. It

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allows transactions between 3D printer owners and people that want to make 3D prints. 3D Hubs is an online service where every 3D printer owner can register and set his availability to print for anyone else. This is a fascinating opportunity that highlight the economic potential of additive manufacturing. Anyone can earn money by

simply owning a 3D printer and a whole new market is created. The experience I had was incredibly positive, since in three days, without doing anything more than uploading online the digital model, I had my complex buildings printed and ready to be showcased at the exam.

5.2.2 PIÙ LAB WORKSHOP The first real approach with a 3D printer was instead on July 15, 2014, at Più Lab, a laboratory in the Department of Chemistry, Materials and Chemical Engineering “Giulio Natta” of Politecnico di Milano. Directed by Prof. Ing. Marinella Levi, the laboratory aims at exploring FFF desktop 3D printing through a multidisciplinary approach that combine engineering and design, studying materials and machines but also applications and innovations possible thanks to this technology. To diffuse the 3D printing culture in Politecnico di Milano, Più Lab hold introductory workshops where they explain the theoretical basis of the technology

but also let students work with machines and make their own (first) 3D printed objects. The participation to the workshop allowed me facing for the first time the vast potentials of filament fused fabrication and 3D printing in general, in particular letting me understand how small it is the gap between digital and physical with such a fabrication technique. At the same time this first experience made clear that it is not possible to 3D print everything nor it is fast the printing process itself.

figure 5.4 +LAB is a team of designers and engineers at the Chemical and Materials Engineering Department of Politecnico di Milano, setting their research on innovative materials for the purposes of additive manufacturing

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5.2.3 MAKERBOT Z18 From the end of July 2014, thanks to Professor Paoletti, I had the chance to work several months with a Makerbot Z18 plastic extrusion 3D printer. The experience started from the unpacking of the machine and its first setup. A deeper study on the machine started in October, and since the beginning it was clear that 3D printing is not as easy as it may seem from outside, taking about two weeks to understand how to control the dozens of settings available during the slicing operation. Many tests has been conducted to analyse different aspects, opportunities and limits of the machine: different layer heights thus different finishings, control of supports for overhanging parts, prints with different materials has been explored. From these tests resulted that the proprietary Makerbot slicing software was limiting the control over the machine, in particular it was not possible to create open curves or points if not included in a closed mesh. Hence, in order

to have a complete control over the printer, analysing software-generated command-lines, I worked on a script that allows to generate the list of commands for the printer (equivalent of the G-Code), directly from the parametric tool Grasshopper. This code would have opened new opportunities in the use of the printer, giving the possibility to avoid the often imprecise slicing passage. Unfortunately, such a work would have required months to reach a complete precision and control of all measures and settings. In general, during the period of use, the Makerbot Z18 3D printer, although gave me the opportunity to print some qualitative pieces, put in evidence most of the limits of FFF technology as it is at the moment of writing. Printing error and failures are still too common on such machines, the control of supports on the software does not grant sufficient results after printing, with difficulties in removal and consequent poor finishing, thus drastically

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limiting shape possibilities for overhanging parts. Moreover, each object requires even drastically different settings from the others,

costing time in the setup and often more than one print to get acceptable results.

5.2.4 VISITING THE ITALIAN 3D PRINTER PRODUCERS To have a more complete awareness of what 3D printing is and to hear ideas and opportunities from experts in the field, we contacted main italian producers of plastic extrusion 3D printers. This meetings resulted important also for the project, since the idea was to create a sort of ‘Printing Factory’, consisting of a series of 3D printers working at the same time on the components which constitutes the pavillion, emphasizing on the big change in the production chain that additive manufacturing can bring: groups of small and inexpensive machines can work at the same time to produce elements for construction. The first visit was done in the headquarter of WASP, close to Ravenna. WASProject was born in 2009 from a challenge that art throws to science: finding solutions to make dreams

true. Under the inspiring guidance of Massimo Moretti, founder and main developer of the project, starting from the small format 3D printer, WASP is trying to develope a printer capable of laying down clay or concrete, to move into a bigger printer for houses with a very low cost. They’re idea is that thanks to 3D printing is possible to transform slums into natural villas. WASP headquarter comprise a office where, as Moretti explained as, workers and everyone who has ideas to be developed can share information and knowledge about 3D printing, and an assembly and testing area, where machines are assembled and tested. Thanks to Massimo Moretti, we had the chance to see both small plastic and clay machines and the huge 6 meters ‘Big Delta’ clay and concrete printer in action, discussing

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about their technical features and the directions of their future research. The Big Delta still show limits as far as precision is concerned, in particular after drying. Moreover the process has important limitations in shape and overhanging parts generation. Hence, theyâ&#x20AC;&#x2122;re working both on materials, studying everyday new clay and concrete mixtures, and printer technology to improve printing quality and speed. The second visit was kindly offered by Maximilian Turchi, founder of Kloner, a semiprofessional plastic extrusion 3D printer

producer. Kloner both project and fabricate its printers, thus we had the chance to visit the laboratory where printer parts are produced. The company was originally producing biomedical machines, but in 2012, as Maximilian explained, the increasing interest in 3D printing around the world was a great opportunity and he decided to design, starting from his biomedical machines, his own 3D printer, to prototype parts, for his and other companies. His engineering attitude is evidently transferred into production and marketing methods. The

figure 5.5 The 6-meters huge â&#x20AC;&#x2DC;Big Deltaâ&#x20AC;&#x2122; clay and concrete printer developed by the Italian producer WASP in action

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company does not work to sell machines, but to offer high quality 3D printers to it costumer. By the end of January 2015 we also had the chance to visit offices and laboratory of Sharebot, the biggest producer of desktop 3D printer in Italy, located in Nibionno, close to Lecco. The company has dramatically expanded its market in 2014, and starting from plastic extrusion 3D printer, they also expanded their technology, researching on SLA and DLP machines.

These visits granted me a broader knowledge of what is the potential impact of additive manufacturing in the italian, and worldwide, industry and economy. Moreover the possibility to test and see different machines allowed to have a deeper understanding of the actual technological potentials and limitations of both filament and clay extrusion 3D printing. Finally, the inspiring discussions with producers offered new points of view about the idea of a 3D printed architecture.

figure 5.6 Kloner is an Italian plastic extrusion 3D printer producer run by Maximilian Turchi

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REFERENCES Duro-Royo J., Zolotovsky K., Mogas-Soldevila L., Varshney S., Oxman N., Boyce M., Ortiz C.(2014) MetaMesh: A Hierarchical Computational Model for Design and Fabrication of Biomimetic Armor Surfaces. Computer-Aided Design, Elsevier , Vol. 60, pp. 14–27. Hansmeyer, M., Dillenburger, B. (2013) Towards a Micro-tectonic in Architecture. In Serbian Architectural Journal. Niklas, K. J. (1992) Plant biomechanics: an engineering approach to plant form and function. University of Chicago Press, Chicago. OPM (2014) OXFAB™ Industrial Parts. http://www.oxfordpm.com/industrial_parts.php. Accessed 27 December 2014. Oxman N. (2009) Material-Based Design Computation: Tiling Behavior. ACADIA 09: reForm( ) – Building a Better Tomorrow. Proceedings of the 29th Annual Conference of the Association for Computer Aided Design in Architecture (ACADIA), Chicago, Illinois, 22-25 October., ISBN 978-09842705-0-7 Oxman N. (2010) The New Structuralism: Design, Engineering and Architectural Technologies. Architectural Design, Special Issue:, vol 80, issue 4, pp. 78-85. John Wiley & Sons, Ltd., London.

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“A revolution in manufacturing is thou limited without a revolution in design processes.” Beckett, 2014

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6.1 GOALS The following experiment is part of a broader research currently being developed by ACTLAB. The main goal was the definition and the fabrication of an innovative construction system for building skins which mechanical behaviour has been optimized in a lightweight multiperformative structural model with the use of layer-based technology. The project attempts at capitalising on of the main advantages of additive manufacturing, i.e. the possibility to fabricate literally infinite number of different components with no significant increase in cost and production time together with the potential of creating complex hollow shapes otherwise impossible with traditional techniques.

These characteristics, intrinsic to the technology, brought to novel ways for implementing optimization processeses in the fields of architecture and construction. Additive manufacturing gives the possibility not only to design but also to produce optimized heterogeneous and anisotropic structures which respond to a system of forces and targets. The main focus of the following experiment though has been the development of a comprehensive parametric process of iterative analysis and optimization rather than the fabrication of a final product. Subsequently, the innovative methodology would be implemented into the design of a temporary 3D printed pavilion which has been also the occasion to investigate the research line.

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6.2 ASSUMPTIONS As already discussed in the first part of the thesis, we are nowadays witnessing a constant evolution of 3D printing technologies. The current ongoing research on materials adapted for the needs of additive manufacturing, brings at our disposal novel high-performance materials with stronger chemical, physical and mechanical properties. Based on these advances in the field, we can assume that future developments would bring improvements also in terms of layer bonding resistance, flexural strength, resistance to environmental factors or flammability. Another fundamental factor being under development is the potential to print full-

scale objects. Several projects are already taking advantage of scaled versions of desktop plastic 3D printers, with a printing volume of more than a cubic meter. In the near future these bigger machines could become a standard in the field, thus allowing fabrication of larger components for construction. Furthermore, the process of layered manufacturing would become faster and more stable, offering bigger freedom and higher level of precision. These advancements combined with the fact that different patents on additive manufacturing technologies would expire, offers a future drastic reduction of costs of both machines and materials.

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6.3 OPERATIVE FRAMEWORK 6.3.1 MATERIAL SYSTEM The definition of a proper material system is fundamental for the efficient development of a lightweight system. Currently, plastics such as ABS, PLA, acrylate, photopolymer, polyamide (nylon), epoxy, polycarbonate and PMMA (acryl glass) are used for additive processes. Material mixtures might be modified for specific applications like aeronautical engineering, in order to impart specific properties on the materials. Polyamide, for example, was modified so that it could be classified as ‘incombustible’ and therefore used for aeroplanes. Some of these techniques have been later introduced to the general AM market bringing high performance plastics at our disposal. The introduction of these novel plastic materials opens up new potential applications for architecture and more specifically for building façades.

In this specific case, the skin system would be entirely fabricated with polylactic acid (PLA), one of the most widely used plastics in fused filament deposition 3D printing. PLA is a biodegradable thermoplastic aliphatic polyester derived from renewable resources, such as corn starch or sugar cane. This makes it more environmental-friendly and suitable for a trial and error research methodology. It is harder than ABS (a oil-based plastic largely used in both injection moulding and additive manufacturing), melts at a lower temperature (around 180°C to 220°C), and has a glass transition temperature between 60-65 °C. The tensile strength of PLA can be attested around 50 MPa, whereas for ABS it is 33 MPa. However there is not yet a strict standardization in the production, and even two material reels from the same producer can have different mechanical and thermal characteristics.

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Finally, itâ&#x20AC;&#x2122;s important to mention that additive manufacturing technology implies that material is deposited layer upon layer, thus generating slight discontinuities (depending on the accuracy and optimization of the process) and weaker

bonding between layers. Hence, although PLA has bigger boundary resistance than other materials, 3D printed objects have anisotropic behavior, being stronger perpendicular to layers than parallel to them.

6.3.2 FABRICATION AND SOFTWARE FRAMEWORK As already discussed in Chapter 5, the fabrication of small-medium building components seems to be most appropriate one, taking into consideration the current level of development of additive technologies and the balance required between precision and manufacturing speed. In this case, the active research has been developed mainly using a Makerbot Z18 3D printer, that, although being the biggest consumer desktop 3D printer available on the market, set the boundaries for fabrication to its 31,2 x 31,2 x 45,7 cm printing volume. This turned out to be one of the design constraints that has been considered during optimization process, in particular during the tessellation phase.

The Z18 3D printer itâ&#x20AC;&#x2122;s a traditional plastic extrusion 3D printer with X and Y axis movement of the printing head and Z axis movement of the build plate. Its innovative feature is that it is completely closed allowing a control of the temperature inside the build chamber, which may grant better results in particular for big objects. Unfortunately the Z18 machine has many limitations and problems which often led to failures and rarely allowed to take advantage of the remarkable printing volume. Among them it is worth to mention the slowness of the process, which is one of the limitations of big size FFF 3D printing in general. The 3D modelling software Rhinoceros coupled with its open-source parametric

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plugin Grasshopper and a series of add-ons for it has been used to design and analyse tests and models. In particular Grasshopper plugin Millipede was used for the mechanical analysis. Mesh-fixing processes are done with MeshMixer and NetFabb Basic. For the slicing Makerbot

Desktop has been largely used, but also Cura has been tested. Due to some limitations and constraints of these slicing softwares, a script for generating the G-Code directly from Grasshopper has been developed and tested.

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6.4 TOP-DOWN SHAPE DEFINITION The final aim of the project was the development of an experimental operative workflow more than of a discrete end-use product. Since the set of parametric operations defined throughout the research should be applicable to any kind of rational or freeform shape, the general form of the pavilion has not been set as a main focus. Hence, I opted for working on a closed shape which grants sufficient overall stability. Its genesis derives from hyperbolic-like structures. The hyperbolic structures have a negative Gaussian curvature. This means they

curve inward rather than outward or being straight making them superior in stability towards outside forces than â&#x20AC;&#x153;straightâ&#x20AC;? buildings. However, I shaped a considerable curvature of the section thus increasing the overhanging angle. This revealed a relevant quantity of stresses that I used to base mechanical analysis and optimization on. The temporary pavilion is going to have an ellipsoid base with radiuses 1 m and 1.2 m, a top ellipsoidal ring of 3.2 and 2.7 meters and the smaller part is described by a circle of 1.2 m radius. The total height of the design is 4.25 meters.

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6.5 TOPOLOGY ANALYSIS The overall form has been then analysed for mechanical optimization. The methodology of computation used is based on Solid Isotropic Material with Penalisation (SIMP) topology optimization method, generating informations regarding the layout of material for a given set of loads and boundary conditions such that the resulting layout meets a prescribed set of performance targets. This is distinct from shape optimization since typically shape optimisation methods work in a subset of allowable shapes which have fixed topological properties, such as having a fixed number of holes in them. In some cases, proposals from a topology optimisation, although optimal, may be expensive or infeasible to manufacture. These challenges can be overcome through the use of manufacturing constraints in the topology optimisation problem formulation. Using manufacturing constraints, the optimisation yields engineering designs that would satisfy practical manufacturing requirements. In some cases, additive manufacturing technologies are used

to manufacture complex optimized shapes that would otherwise need manufacturing constraints. Topology optimisation has been implemented through the use of finite element methods for the analysis. To be able to manage inputs and outputs of the analysis and create a linear workflow from shape to optimization to construction components, the analysis has been implemented using Millipede plugin for Grasshopper, the main digital working environment for the project. Millipede is a structural analysis and optimization component that allows for very fast linear elastic analysis of frame and shell elements in 3D, 2D plate elements for in plane forces, and 3D volumetric elements. All systems can be optimized using builtin topology optimization methods and have their results extracted and visualized in a variety of ways. In the experiment I opted for using the built-in topological analysis for frames and shells, which elaborates any surface and analyses it given a set of loads and boundary conditions.

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6.5.1 SHELL TOPOLOGY ANALYSIS VARIABLES A series of variables have been set to define the system. Throughout the research, many attempts have been done to understand the best settings that could bring to a considerable optimization of the structure. Topology optimization is often used to give general directions during the design phase, rather than to produce a buildable and functionally sized object. For my experiment, is was fundamental to get analysis results and to interpret them in order to inform the base surface, starting point of my exploration. For this reason some values might have been oversized, with the purpose of emphasizing results, such as stresses and material distribution. Furthermore, the software enabled me to define the material properties. Since finding reliable data about PLA was quite difficult, I used the mechanical properties of Glass Reinforced Plastic (a type of high-grade plastic) as a reference for the experiment (E=2.6x1010 Pa,

v=0.28, p=1800 kg/mÂł). Another variable that has been taken into account in the computation process is the thickness of each element of the system. At the same time, one of the objectives of the project was to optimize this parameter in function of the results of the analysis. Hence, after different attempts and evaluation of the results, I opted for an ambitious dimensioning of the structural thickness of 5 cm. A relevant issue when topology optimization method is concerned, is the evaluation of the self-weight of examined region. For this purpose, in Millipede software it is introduced a Self Weight Coefficient. It is a number that multiplies all the loads due to the self weight of the structure. For most optimization problems it should be set to 0 as it can induce a non-convergent feedback behavior in the optimization algorithm: as material gets redistributed, the weight distribution changes as well, which results in changes in the optimal

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solution. However, for the purposes of the research, it has been of great importance to consider how the structural skin can sustain itself, or the directions and distribution of weightâ&#x20AC;&#x2122;s forces. That is one of the main reasons why the topological analysis for frames and shells has been used, which does not automatically redistribute material thus does not induce errors in the evaluation of weight distributions during iterations. Topology optimization methods aim at optimizing material distribution given a target density. My intention was not to directly apply the material reduction resulted from analysis, but to have informations to inform my optimization methods. Different target densities have been considered before attesting at 0.5 as the best solution, which grants both stable results with different shapes and clear indications as a result. A characteristic of SIMP method of topology optimization is that material density is penalized (i.e. the density is raised to some large exponent, say >=3) in order to discourage the formation of intermediate densities (i.e. between 0 and 1) that have no real physical significance in

structural optimization. Millipede implemented this function, and after different tests on the shape, between 1.5 and 3 (smaller or larger values always brought to failures in the analysis) the coefficient gave almost the same results. The last parameter to be set directly into the Millipede engine is the number of iterations of analysis and optimization it runs. Generally, with the final settings of all aforementioned variables, I found good and defined results with around 100 iterations. An important external factor that mostly determined the definition of the result and time of analysis, is the mesh definition. Giving a coarse mesh would result in an inaccurate and not reliable optimization, whereas a too precisely defined mesh - in a very long time of analysis. Different tests have been made, which shows big differences in the definition of results. The final choice for this experiment, since many trials were needed, has been to use a medium resolution, able to give consistent results but also acceptable computation times.

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6.5.2 INTERPRETATION OF THE TOPOLOGICAL ANALYSIS The iterative computational analysis of Millipede gives a number of informations regarding stresses on the structure. The main result of stress analysis is an optimized quantitative layout of material over the shape, which removes material in less stressed areas (black areas) and reinforce areas where stresses are relevant (white areas). Such an approach, however, parallelly produces a field of forces, which describes quantity and direction of stresses along the volume. This component calculates the two principal stress lines emanating from a single point. Stress lines are curves that at each point are tangent to one of the principal stress directions. For every cell of the mesh Millipede generates planes at every center with axes aligned with principal stress directions, together with the normal displacement in that point [m], and the

Estimated Maximum Von Mises stress for all layers of each quad [N/m2]. Moreover, an Optimization Factor, a number from 0 to 1, designate the relative strength of thickness multiplier during the optimization process. This mathematical model must then be translated into a tectonic which properly responds to the informations given. For this purpose, quantitative informations and vectors have been interpreted to inform the initial surface and generate a new structural layout. To do that, stress lines have been filtered by the the material layout, in order to obtain a series of curves representing the main directions of forces in the most stressed areas. This procedure allowed me to reparametrize the hyperboloidal surface I started from, obtaining a new isocurves layout. Isoparametric curves, commonly named as isocurves, are curves of constant

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u- or v-value on a surface. Rhinoceros software uses isocurves and surface edge curves to visualize the shape of NURBS surfaces.

Therefore, the resulting surface integrates quantitative and qualitative informations from the analysis and will guide the consequent multi-scalar optimization

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6.6 PERFORMATIVE TESSELLATION As already mentioned, working on performative envelopes made by small scale components, the issue of tessellation is crucial. Tiling is a necessity that cannot be avoided when implementing additive manufacturing techniques, making the resulting component more stable and accurate. Nevertheless, a tessellation allows for easy and compact production lines, and reduce at the minimum transportation costs and maneuverability risks. The question arising is how to subdivide a facade in components without losing those performances implemented in the design. Can tessellation become a reinforcement rather than a weakness for the building envelope? A performative optimization of the overall shape is not much effective if not supported by an appropriate tessellation, able to respond to the system of forces acting on the structure. Along with the experiment, the attempt is of calibrating the tessellation system in order to

respond mechanical requirements, basing the process on FEM analysis results. The system has been developed by means of subdivision of the previously informed surface. Similarly to form optimization, different approaches have been developed as far as tessellation is concerned. However, its logic is always informed by the rebuilt isocurves of the volume, creating more rigidity and strength to parts that undergo major stressing. After various attempts with triangular, hexagonal, stellated and other tessellations, I found out that none of them was keeping trace of the direction of loads, transferring them directly to the ground. Moreover, for the mechanism of layering on which additive manufacturing is based on, the printed pieces are much stronger perpendicular to the layers than parallel to the layers as they can split along layer boundaries. For these reasons I developed a curvilinear

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tessellation that directly follows the values of the re-parametrized surface. The algorithm is thus generating tiles that are always perpendicular to the direction of stresses. Moreover, I integrated in the discretization

process all geometric and dimensional limits imposed by the fabrication process of plastic extrusion 3D printing and in particular by the Z18 machine used for testing. Every printed piece should thus be fitting a bounding box

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that correspond the printing dimensions of the machine, i.e. 30,5 x 30,5 x 45,7 cm and, since supports generation is affecting time and cost of the object, and also model precision and finishing, implementing in the algorithm

a control over the maximum printing angle. This is the angle that occurs between printing plane and the vector between one layer and its precedent, that generally should not be over 45Â° to assure a good level of accuracy.

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6.7 MULTI-SCALAR OPTIMIZATION OF THE STRUCTURAL PATTERN 6.7.1 THICKNESS OPTIMIZATION In order to optimize the mechanical behavior of the designed skin, a further step is the operation of informing and optimizing the general thickness of the geometry, according to analysis results. The reparameterized surface integrates mapped densities as well as stress directions, giving the opportunity to optimize form both according to density and to stress directions. Different trials have been made with two distinct approaches. The first one is the development of a script that corrugates the skin according to isocurves density and follows their direction, thus giving rigidity

in more stressed parts and being always parallel to stress direction. A different approach has been followed in the second set of trials. Density informations given by Millipede are mapped onto the isocurves and the initial surface has been thickened according to these values, producing as a result a volume which is thicker where more material is needed, i.e. structural areas, and thinner in areas where there is minimal stress. The script I generated allows to parametrize the minimum thickness, and to map the domain of initial values on a new domain which defines minimum and maximum displacement of the volume

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with respect to the initial surface. The second approach turned out to be more appropriate and clean with respect to the field of application. In particular,

when the complexity of the stress pattern is higher, the curve-corrugation approachâ&#x20AC;&#x2122; does not result in a precise and appropriate model.

6.7.2 MICRO-STRUCTURAL ORGANIZATION A tessellation of a construction system is generating a series of discontinuities in the transfer of loads, resulting in potentially weak points, particularly where the connections are located. Moreover, traditional construction techniques hardly enable the possibility to optimize quantity and direction of resistant sections along a volume. In other words, generally traditional fabrication methods do not allow the control of heterogeneity and anisotropy of material. As already discussed, additive manufacturing allows the fabrication of hollow pieces, and moreover it enable the production of an internal microstructure which responds to different factors. This may help to reinforce pieces when discontinuities and connections are concerned, at the same time guaranteeing a substantial material saving and reduction of weight, very important when structural skins are considered. Moreover, a broader research is currently focusing on the possible

integration of different performances besides mechanical ones, such as visual screening or thermal insulation. Hence, the generation of different patterns have been attempted, each of them guaranteeing a different visual filter, volume to area ratio and mechanical behavior. The process of micro-structure generation is computationally controlled by the data receive from analysis, tessellation and further external factors (e.g. solar irradiation). Nevertheless the whole process is controlled to match fabrication constraints. In fact plastic extrusion machines, as already described before, have hurdles when the angle between one layer and the previous one is too small,which means that the material does not have enough base to adhere on. This means that generated micro-structural patterns should not have horizontal elements. The goal of having a lightweight structure and the idea of a possible integration of visual

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control in the process led to the decision of focusing on permeable patterns, thus avoiding continuous surfaces and using pattern composed of frames elements. To better control angles the final decision was to focus on octahedron as main volumetric cell

to describe the three-dimensional pattern. Varying direction and density of the pattern reflects natural systemsâ&#x20AC;&#x2122; ability to optimize material distribution reacting to different systems of stresses and external influences (e.g. bones, trees, etc.).

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6.8 FINAL RESULTS AND FUTURE DEVELOPMENTS The final result of this thesis is an hybrid computational workflow of analysis and optimization, which balances between different targets and boundary conditions. First and foremost, every optimization choice has been set in the domain of additive manufacturing. Every step includes a control check that enables a supervision over both maximum dimensions of printed pieces and minimum definition of printed elements but also a control to avoid overhanging parts. Furthermore, since additive manufacturing produces anisotropic objects due to the comparatively weaker bonding links between layers, a tessellation process has been defined and informed in order to achieve direction of the layers always perpendicular to local stresses. Moreover, the computational process includes a multi-scalar optimization algorithm

that, working with topology optimization mechanisms, informs the transition from a concept model to a construction model. The tessellation of the design is thus a variable dimension and direction tiling system which responds to the technological boundary conditions, but also reacts to mechanical stresses, varying its density and directions. The algorithm consequently organizes material distribution at the macro-scale in a heterogeneous way, thickening the input model where major stresses are located. It also organizes micro-structural patterns along stress directions, increasing density as a reaction to stresses and orienting towards force directions. This process can be further developed and integrated in different ways. A first step towards the definition of a construction system, would be the development of an appropriate assembly

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system. Joints could be completely integrated in printed components, or different hybrid solutions can be found combining 3D printed joints with traditional screwing and binding systems. Along with the integration of joints in the components, the micro-structural behavior would respond and adapt to stress analysis of the joints, correspondingly reinforcing defined fracture areas. Another interesting implementation of this method, being the main objective of a collaboration on a broader research together with ACTLAB, is to integrate multiple performances into the optimization process. This is a particularly compelling approach to be applied on building skins, since envelopes are filters between external and internal environment, and both thermal performances, visual impact and light filtering can be performative aspects to be controlled. A third interesting research line is the possibility given by more expensive additive machines to work with different materials, which opens incredible potentials in the definition and fabrication of heterogeneous and anisotropic performative systems.

Besides the possible directions of research, the computational workflow described can be further improved and extended. Actual 3D modelling softwares are simply describing the external surface of an object and do not allow the complete exploitation of three-dimensional space and the possibility to model internal parts of hollow objects.This makes the process of working into a multi-scalar environment slow and complicated. Moreover the description of complex shapes relies vastly on intricate and heavy meshes, limiting the analysis and computational process. For this reason two researchers from Harvard University are working on the development of an innovative 3D modelling software dedicated to multi-materic 3D printing. The software is called Monolith and is a volume modelling software which gives the opportunity to manipulate three dimensional images made of voxels. Therefore the user can define rasterization patterns with variable degrees of optical and elastic anisotropy. This is another step towards a dedicated modelling environment that will unlock the infinite range of possibilities given by 3D printing.

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ON THE IMPACT OF DIGITAL FABRICATION: Bollinger K., Grohmann M., Tressmann O. (2010) Structured Becoming: Evolutionary Processes in Design Engineering. In: Oxman R., Oxman R. (2010) The New Structuralism. AD, vol.80, No. 40. John Wiley & Sons, London. Naboni, R., Paoletti, I. (2014) Advanced Customization in Architectural Design and Construction. Springer Verlag. Reiser J., Umemoto N. (2006) Atlas of novel tectonics. Princeton Architectural Press, New York. Troxler P. (2013) Making the 3rd industrial revolution. In: Walter-Herrmann J, BĂźching C (ed) FabLabs: Of machines, makers and inventors, Transcript Publishers, Bielefeld. ON THE ADDITIVE MANUFACTURING TECHNOLOGY: 3D Prototypes and Models (2013) 3D Printing Materials, Terminology and Specifications. http://3dprototypesandmodels.com.au/3d-printing-terminology-specifications. Accessed October 2014. 3T RPD Ltd (2013) Metal Additive Manufacturing (AM) using Direct Metal Laser Sintering (DMLS). http://www.3trpd.co.uk/dmls.htm. Accessed 18 October 2014.

247

BIBLIOGRAPHY

Barnatt, C. (2013) 3D Printing: The Next Industrial Revolution. CreateSpace Independent Publishing Platform. Barnatt, C. (2014) 3D Printing. http://www.explainingthefuture.com/3dprinting.html. Accessed 14 September 2014. Canessa, E., Fonda, C., Zennaro M. (2013) Low-cost 3D Printing for Science, Education & Sustainable Development. ICTP - The Abdus Salam International Centre for Theoretical Physics, Trieste. Deekard, C. R. (1989) Method and apparatus for producing parts by selective sintering. US Patent: 4,863,538. The University of Texas System, Austin, Tex. Gibson I., Rosen D., Stucker B. (2014) Additive Manufacturing Technologies. Springer, NYC. Karunakaran, K.T. et al (2012) Rapid manufacturing of metallic objects, in Rapid Prototyping Journal. Lipson H., Kurman M. (2013) Fabricated: The New World of 3D Printing. John Wiley & Sons Ltd., Chichester. Local Motors (2015) 3D Printed Car. www.localmotors.com/3d-printed-car. Accessed 12 February 2015. OPM (2014) OXFABâ&#x201E;˘ Industrial Parts. http://www.oxfordpm.com/industrial_parts.php. Accessed 27 December 2014.

248

Torabi, P., Petros, M., Khoshnevis, B. (2014) Selective Inhibition Sintering: The Process for Consumer Metal Additive Manufacturing. 3D Printing and Additive Manufacturing. September 2014, 1(3), pp. 152-155. University of Texas at Austin (2013) Selective Laser Sintering, Birth of an Industry. http://www.me.utexas.edu/news/2012/0712_sls_history.php. Accessed 27 November 2014. Wikinvest (2014) Stratasys, Annual Report. http://www.wikinvest.com/stock/Stratasys_(SSYS)/Products. Accessed 29 December 2014. ON THE ADDITIVE MANUFACTURING FOR ARCHITECTURE: AGB.com (2014) 3D Printed House: Could It Be A Sustainable Solution for Future Construction in Asia? http://www.asiagreenbuildings.com/3d-printed-house-sustainable-solution-futureconstruction-asia/. Accessed 17 October 2014. Arup (2014) Construction steelwork makes its 3D printing premiere. http://www.arup.com/News/2014_06_June/05_June_Construction_steelwork_makes_3D_ printing_premiere. Accessed 21 August 2014. Balinski B. (2014) Chinese company 3D prints 10 houses in a day from recycled material. In: Architecture & Design, Cirrus Media. http://www.architectureanddesign.com.au/news/chinese-company-3d-prints-10-houses-in-aday-from Accessed on 25 May 2014

249

BIBLIOGRAPHY

Buswell R., Soar C., Gibb A., Thorpe T. (2007) Freeform construction: Mega-Scale Rapid Manufacturing for Construction. Automation in construction, 16 (2), pp. 224-231. Elsevier Data Clay (2013) Building Bytes. http://www.data-clay.org/projects/Building%20Bytes/index.html. Accessed 12 January 2015. De Kestelier, X and Buswell, R (2009) A digital design environment for large-scale rapid manufacturing, ACADIA 09: reForm: Building a Better Tomorrow - Proceedings of the 29th Annual Conference of the Association for Computer Aided Design in Architecture, pp.201-208. Dini E. (2010) What is D-shape. http://www.d-shape.com/cose.htm Accessed 6 June 2014 DUS Architect (2014) 3D Print Canal House. http://3dprintcanalhouse.com/. Accessed 21 August 2014. Emerging Objects Corp. (2014) Emerging Objects. http://www.emergingobjects.com/. Accessed 12 September 2014. Gramazio F., Kohler M. (2014) Made by Robots: Challenging Architecture at a Larger Scale. vol. 84, issue 3, pp. 44-53. John Wiley & Sons, London. Le, T.T., Austin, S.A., Lim, S., Buswell, R.A., Gibb, A.G.F. and Thorpe, A. (2011) High-performance printing concrete for freeform building components, fib Symposium Prague 2011, Concrete engineering for excellence and efficiency.

250

Lim, S., Buswell, R.A., Le, T.T., Austin, S.A., Gibb, A.G.F. and Thorpe, A. (2012) Development in construction-scale additive manufacturing processes, Automation in Construction, Vol. 21, Issue 1, pp.262-268. Hack, N., Lauer, W.V. (2014) Mesh-Mould: Robotically Fabricated Spatial Meshes as Reinforced Concrete Formwork. In Architectural Design. Made by Robots: Challenging Architecture at a Larger Scale. Vol. 84, Issue 3, pp.44-53. John Wiley & Sons Ltd., London. Halterman, T., (2014) Philippe Morel Uses 3D Printing for Concrete Structures. http://www.3dprinterworld.com/article/philippe-morel-uses-3d-printing-for-concretestructures. Accessed 5 October 2014 Hansmeyer, M., Dillenburger, B. (2013) Towards a Micro-tectonic in Architecture. In Serbian Architectural Journal. Hansmeyer, M., Dillenburger, B. (2014) Digital Grotesque. http://www.digital-grotesque.com/#5. Accessed 18 October 2014. Khoshnevis, B. (2014) Contour Crafting. http://www.contourcrafting.org/. Accessed 12 October 2014. Massie, C. (2014) Skanska Aims to Commercialize 3D Printing with Concrete. http://www.architectmagazine.com/technology/skanska-aims-to-commercialize-3d-printingwith-concrete_o.aspx. Accessed 27 November 2014.

251

BIBLIOGRAPHY

Novedge (2014) Conversations on 3D Printing and Architectural Design. http://blog.novedge.com/2014/12/conversations-on-3d-printing-and-architectural-design.html. Accessed 12 November 2014 Peters, B. (2012) Building bytes. 3D printed bricks. http://buildingbytes.info/. Accessed 18 October 2014. Sabin J., Miller M., Cassab N., Lucia A. (2014) PolyBrick: Variegated Additive Ceramic Component Manufacturing (ACCM). 3D Printing. vol. 1, No.2, DOI: 10.1089/3dp.2014.001. Mary Ann Liebert, INC. Smith | Allen (2013) Echoviren. In: ArchDaily. http://www.archdaily.com/419306/echoviren-smith-allen/ Accessed 14 December 2014. Sher, D. (2014) Emerging Objects is Building the Future One 3D Printed Brick at a Time. http://3dprintingindustry.com/2014/11/18/emerging-objects-3d-printing/. Accessed 14 November 2014. Strauss, H. (2012). AM envelope: The potential of additive manufacturing for facĚ§ade construction. CreateSpace Independent Publishing Platform. Van der Kley M. (2014) Project Egg. http://projectegg.org/project-egg/. Accessed 11 January 2015. Vinnitskaya, I. (2012) KamerMaker: Mobile 3D printer inspires potential for emergency relief architecture. http://www.archdaily.com/274798/kamermaker-mobile-3d-printer-inspires-potential-foremergency-relief-architecture/. Accessed 28 October 2014

252

Voxeljet (2014) Casting of Concrete. http://www.voxeljet.de/en/case-studies/case-studies/casting-of-concrete/. Accessed 7 October 2014. Wang L (2014) Chinese company assembles 10 3D-printed concrete houses in a day for less than $5,000 each. In: Inhabitat. http://inhabitat.com/chinese-company-assembles-ten-3d-printed-concrete-houses-in-oneday-for-less-than-5000-each/winsun-3d-printed-houses-7/, Accessed 30 May 2014 Wheeler A. (2014) An Interview with Daniel BĂźning -Talking 3D Printing, Art & Architecture. 3D Printing Industry. http://3dprintingindustry.com/2014/07/13/interview-daniel-buning-talking-3d-printing-artarchitecture/. Accessed 8 January 2015. Winston, A. (2014) Arup unveils its first 3D-printed structural steel building components. http://www.dezeen.com/2014/06/11/arup-3d-printed-structural-steel-building-components/. Accessed 17 September 2014 ON OPTIMIZATION: Brackett, D., Ashcroft, I., Hague, R. (2011) Topology optimization for additive manufacturing. Twenty Second Annual International Solid Freeform Fabrication Symposium. pp. 348-362. Austin, Texas, USA.

253

BIBLIOGRAPHY

Gu, Wenjiong (2013) On Challenges and Solutions of Topology Optimization for Aerospace Structural Design. 10th World Congress on Structural and Multidisciplinary Optimization. Orlando, Florida, USA. Jaffe, B. H. (2013) Topology Optimization in Additive Manufacturing: 3D Printing Conference (Part 5). http://on3dprinting.com/2013/04/23/3d-printing-conference-5-topology-optimization/ Accessed 8 December 2014 On3DPrinting (2014) Airbus Envisions a 3D Printed Future. http://on3dprinting.com/2014/04/04/airbus-describes-3d-printed-future. Accessed 12 December 2014. ON MATERIAL ORGANIZATION: Bar-Cohen, Y. (2006) Biomimetics : Biologically Inspired Technologies. CRC/Taylor & Francis, Boca Raton, FL. Beckett R., Babu S. (2014) To the Micron: A New Architecture Through High-Resolution Multi-Scalar Design and Manufacturing. In: Sheil B. (2014) Architectural Design. Special Issue: High Definition: Zero Tolerance in Design and Production. vol.84, issue 1, pp. 112-115. John Wiley & Sons, Ltd., London. Beckett R. (2015) Interface /4. http://www.richard-beckett.com/interface-4.html. Accessed 8 January 2015. Duro-Royo J., Zolotovsky K., Mogas-Soldevila L., Varshney S., Oxman N., Boyce M., Ortiz C.(2014)

254

MetaMesh: A Hierarchical Computational Model for Design and Fabrication of Biomimetic Armor Surfaces. Computer-Aided Design, Elsevier , Vol. 60, pp. 14â&#x20AC;&#x201C;27. Gibson, L. J., Shercliff, H. R. (1995) The mechanical properties of natural materials. II. microstructures for mechanical efficiency, Proceedings Lond. AR. Soc., Vol. 1, pp. 141â&#x20AC;&#x201C;162. Heinz P., Herrmann M., Sobek W. (2011) Functionally Graded Building Components. University of Stuttgart Institute for Lightweight Structures and Conceptual Design. Production procedures and fields of application for functionally graded building components in construction. Zukunft Bau, ILEK. Menges, A. (2012) Material Computation: Higher Integration, in Architectural Design: Morphogenetic Design, Menges A. ed., Wiley, vol. 82, no. 2, pp. 14-21. Niklas, K. J. (1992) Plant biomechanics: an engineering approach to plant form and function. University of Chicago Press, Chicago. Oxman N. (2009) Material-Based Design Computation: Tiling Behavior. ACADIA 09: reForm-() Building a Better Tomorrow. Proceedings of the 29th Annual Conference of ACADIA, Chicago, Illinois, 22-25 October 2009. Oxman N. (2010) (a) Material-based Design Computation. Ph.D. thesis, MIT Oxman N. (2010) (b) Structuring Materiality: Design Fabrication of Heterogeneous Materials. In Architectural Design, Special Issue: The New Structuralism: Design, Engineering and Architectural Technologies, Oxman Rivka, Oxman Robert (eds.), vol. 80, no.4, pp. 78-85, London.

255

BIBLIOGRAPHY

Oxman N. (2011) Variable Property Rapid Prototyping. Journal of Virtual and Physical Prototyping (VPP), 6:1, 3-31 Oxman N., Laucks J., Kayser M., Tsai E., Firstenberg M. (2013) Freeform 3D Printing: toward a Sustainable Approach to Additive Manufacturing. Green Design, Materials and Manufacturing Processes published by Taylor & Francis , ISBN: 978-1-138-00046-9. Stoneham A., Harding, J. (2003) Not too big, not too small: The appropriate scale. Nature Materials, Vol. 2, No. 2, pp. 77â&#x20AC;&#x201C;83.

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CHAPTER 1 Figure 1.1 Traditional supply chain vs. 3D printing supply chain Figure 1.2 Some statistics on additive manufacturing (3D printing) CHAPTER 2 Figure 2.1 Filament Sculptures designed by generative artist Lia who has been exploring the possibilities of thermoplastic extrusion by defining the location of the printhead, the speed of the movement and the amount of filament that should be extruded Figure 2.2 The Replicator 2 - a market-leading desktop 3D printer from Makerbot Industries (MBI) Figure 2.3 A model printed with a do-it-yourself color blending extruder using a single hot-end with multiple driven feeds Figure 2.4 A design from the 3D Woven collection of functional 3D printed ceramics by Olivier van Herpt which features a weave pattern reminiscent of artisan-made work

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Figure 2.5 Ceramic 3d printing project developed by Unfold in 2009 features a custom software that allows detailed line level control, unlocking a new form language in 3d printing Figure 2.6 A 17 year old developed a prototype for the first desktop based metal 3D printer and launched a Kickstarter campaign to fund the production Figure 2.7 One of the major producers in the field of layer-based manufacturing, voxeljet, has developed a new method for 3D printing which uses phenolic resin binders (Phenolic-Direct-Binding). The picture shows their printing process with temperature management Figure 2.8 American firm 3D Systems has used 3D scanning technology and selective laser sintering combined with robotics in order to create the first exoskeleton to help paralysed patients Figure 2.9 Stereolithographic printer. The viscosity and surface tension of photopolymeric liquids allowed the development of machines where the fabricated object is held upside down in the polymer bath Figure 2.10 Japanese company Unirapid Inc developed a small SLS 3D printer called Unirapid III. The image is an example of its possibilities: a small cube 2.5 x 2.5 x 2.5 mm printed in high resolution with ABSsimilar material for 32 minutes

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Figure 2.11 A sculpture by Amanda Darby developed through digital light processing using the Envisiontec Perfactory 3D printing system Figure 2.12 A design for a helmet called Pneuma 1 designed by Neri Oxman in collaboration with Prof. W. Craig Carter from MIT. Novel multi-material 3-D printing technologies along with new design features such as bitmap printing and property textures have been developed to support material performance and expression CHAPTER 3 Figure 3.1 A close-up image of the 3D-printed steel joint developed by Arup, revealing the complex geometry and the customized design Figure 3.2 Left: Original steel joint produced with traditional technologies; Right: Arup optimized Steel joint fabricated with Direct Metal Laser Sintering (DMLS) additive technology Figure 3.3 The steel canopy framework system which forms a group of branched columns designed by Fletcher Priest Architects

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Figure 3.4 The picture shows the rooftop steel joint covered with the 3D printed polyamide sheaths Figure 3.5 Digital model of the system integrating columns within the 3D printed shroud for the structural joints Figure 3.6 Top: A new technique for fabricating ceramic structural components through the use of desktop additive manufacturing machines developed by Brian Peters (DesignLab Workshop) Down: It takes around 15 minutes to print the parametrically designed bricks Figure 3.7 Nonstandard ceramic brick components for mortarless assembly developed by Sabin Design Lab, in Cornell University Figure 3.8 Quake Column is made of 3D-printed interlocking components, creating a seismically resistant structure Figure 3.9 Left: The project is the result of a long research focusing on the idea of reusing waste and turning it into effective construction material Right: The bricks are hollow and moulded with handles so that they can be easily assembled Figure 3.10 The site-responsive, mimicking 3D printed architectural installation, named Echoviren, designed by the Californian studio Smith | Allen

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Figure 3.11 The ProjectEGG pavillion has been developed as an â&#x20AC;&#x153;openâ&#x20AC;? process involving people from the 3D-printing community from all around the world and as a result comprises 4760 different components Figure 3.12 3D Printed Canal House by DUS architects is a progressive research aiming at 3D printing a full-size house, exhibiting the results from combining tradition and innovative technologies Figure 3.13 Top: 3D Printed Canal House by DUS Architects features a large-scale 3D printer called Kamermaker which is located on the construction site, and exhibits every printing process to the public. Down: The image shows the two fold function of the concrete casting: to increase the compressive structural capacity and to join the separate pieces together through inclined shafts Figure 3.14 Digital Grotesque project focuses on the recent developments on sand-printing technology and tries to exploit the full potential of this technique Figure 3.15 The project demonstrates the precision and the potentials of sand-printing technology and the possibilities it offers in terms of complexity, reduced fabrication cost and aesthetics. Figure 3.16 The innovative technique D-Shape developed by Enrico Dini utilizes inorganic binders to stick sand particles together into a homogeneous synthetic mass. The technology has been developed for the needs of large-scale printing and the application in the construction sector

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Figure 3.17 Left: Dimensional check of a series of sections of the Villa Roccia project Right: Detailed digital model of one of the modules of the project. It comprises openings for pipes and post-tensioned rods, a joinery and tagging system of each piece Figure 3.18 Contour crafting is an experimental project developed by professor Behrokh Khoshnevis, that utilizes thick layer deposition of semi-fluid materials which reduces production time significantly Figure 3.19 Left: The system is a fundamental attempt to transfer rapid production technology to the construction scale and offers a solution to the manufacturing of an entire structure in a single day by utilizing direct layer production Right: The hybrid automated fabrication technique that combines extrusion process for printing the objectâ&#x20AC;&#x2122;s surfaces and an injection filling process for building the objectâ&#x20AC;&#x2122;s core. Figure 3.20 The Concrete Printing project investigates the possibilities to use selective deposition techniques to redesign complex assemblies into integrated panel systems rather than printing monolithic structures Figure 3.21 Left: The concept design focus on adding performance and functionality to walls as additional functions include optimisation of structural, acoustic, thermal and ventilation properties. Right: The technology is based on selective deposition of paste material through an extrusion nozzle which has varying printing resolution capacity. This allows the deposition of both rough materials and fine detail within the same process.

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Figure 3.22 Chinese company WinSun Design Engineering Co. reached the goal of completing the first concrete 3D printed building utilizing a massive 32 by 10 by 6 m machine which sprays a special mixture of cement and construction waste Figure 3.23 Left: The company has estimated savings between 30 and 60 percent of building materials and production time reduced up to 70 percent compared to traditional construction methods Right: One of the main limitations of the WinSun technology is the impossibility to fabricate overhangs or complex and customized forms. Figure 3.24 Concrete casting is a project developed by Philippe Morel for fabricating sand molds with Voxeljet sand printers to be used in combination with ultra high-performance concrete (UHPC). Figure 3.25 Mesh-Mould is a project developed by Gramazio & Kohler research unit in ETH Zurich and addresses the 1:1 construction aspects of loadbearing structures. Mesh-Mould combines formwork and reinforcement into one single robotically fabricated construction system. CHAPTER 4 Figure 4.1 ICD/ITKE Research Pavilion 2010 demonstrates an alternative approach to computational design: the generation of form is directly driven and informed by physical behavior and material characteristics

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Figure 4.2 Generico Chair designed by Marco Hemmerling reveals potential for an ideal 3D-printing-technology application as it allows for an optimal distribution of materials. Figure 4.3 The image shows the stress lines of a bone structure that is inherently optimized to reach maximum performance with minimal resources Figure 4.4 Normal human vertebral bone structure showing micro-scale material organization Figure 4.5 Functionally graded concrete developed by the Institute for Lightweight Structures and Conceptual Design (ILEK) at the University of Stuttgart. Figure 4.6 Natural column project designed by Daniel Buning is an architectural free-form column with an internal three-dimensionally graded heterogeneous microstructure, derived through a structural simulation process. Figure 4.7 Interface /4 is part of an ongoing research on the design potential of additive manufacturing developed by Richard Beckett and his team. The interface explores how optical variability can be achieved through localised channeling and diffracting material structures and is constructed of laser sintered nylon Figure 4.8 Beast is a prototype for a chaise lounge designed by Neri Oxman. It combines structural, environmental, and corporeal performance by adapting its thickness, pattern density, stiffness, flexibility, and translucency to load, curvature, and skin-pressured areas respectively.

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CHAPTER 5 Figure 5.1 The image shows a design proposal for Civil Courts of Justice building in Madrid by Zaha Hadid architects accentuating environmentally adaptive façade Figure 5.2 Arachne is a prototype design for armor by Neri Oxman. Soft and flexible materials are combined and distributed following continuous web morphology to accommodate for multiple functions such as protection, enhanced movement, flexibility and comfort. Figure 5.3 The GEOtube Tower proposal is a scale model for a Vertical Salt Deposit Growth System for Dubai. The model’s modular components were fabricated using translucent salt material developed by Emerging Objects, a subsidiary of Rael San Fratello Figure 5.4 +LAB is a team of designers and engineers at the Chemical and Materials Engineering Department of Politecnico di Milano, setting their research on innovative materials for the purposes of additive manufacturing. Figure 5.5 The 6-meters huge ‘Big Delta’ clay and concrete printer developed by the Italian producer WASP in action Figure 5.6 Kloner is an Italian plastic extrusion 3D printer producer run by Maximilian Turchi

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ACKNOWLEDGEMENTS First and foremost I would like to express my deepest appreciation and thanks my advisors Prof. Ingrid Paoletti and Arch. Roberto Naboni. They introduced me to parametric design and digital fabrication during my academic career and then gave me the opportunity to collaborate in research and project development on these themes. They generously shared their office, machines, time and most of all their profound knowledge during thesis development, allowing me to grow on both professional and personal level. I extend my appreciation to Mariela Tsopanova and Maya Zheliazkova for their precious help, their suggestions and inspiring discussions in the last year. The most sincere gratitude goes to Giorgia, for the presence, love, patience and support she never get me feel the lack of. Finally, a special thanks to my family, which gave me the possibility of being here and sustained me in every step I have ever taken.

Luca

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