LATIGLOSS

MKTC001

Copyright © LATI S.p.A. 2007

12 October 2007

ENGINEERING THERMOPLASTIC STRUCTURAL COMPONENTS AND DESIGN: THE WINNING COUPLE IN THE FURNITURE SOLUTIONS A hinge system for the vertical opening doors in high-end kitchen cabinets: metal alloy replacement with high aesthetic Structural Thermoplastics save weight and costs.

PROBLEM OVERVIEW Reinforced thermoplastics are among the most popular materials used in the growing metal replacement activities.

Almost any industrial sector has been impressed by the advantages of injection mouldable plastics and related cost savings with respect to metal processing.

Performance gap between engineering compounds and metal alloys has also been narrowing during the last decade thanks to the continuous research and development progress in the field of reinforced polymers and related process technologies.

a clear concept describing a rather complicate device, obtained by the mean of an extended engineering and design procedure.

The whole system is composed by different parts: • •

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A second plate keeping in place all the parts;

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A safety cover enclosing the hinge system;

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A third plate constrained to the moving door via the leverages.

The first plate onto which all components are mounted;

PROCESSING THE PLATE

A multiple leverage system whose movement is smoother thanks to a braking gas piston;

The target focused on EFFEGI was to replace zamak alloys to cut weight and cost of metal components.

Advanced plastics are daily job for LATI, one of the most important independent European compounders, and the here discussed EFFEGI BREVETTI project development testifies how fruitful can be a tight partnership between 60 years experienced material experts and smart designers, skilled in the field of top notch furniture engineering.

THE PROJECT IN ITSELF A sophisticated hinge system moving the vertical opening doors of hanging wall units dedicated to high-end kitchens:

Fig. 1: the complete hinge system

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MKTC001

Copyright Š LATI S.p.A. 2007

12 October 2007 geometric features of the plate as well as in the very quick gate freezing rate, a phenomenon leading to a severe reduction of packing pressure efficiency during the last phase of the moulding process The most relevant problem was the failure of the plastic plate during preloading trials.

Fig. 2: the reengineered part

All the parts belonging to the hinge system were produced with metal and it is evident how interesting savings might ensue from the introduction of mouldable technopolymers in the project.

relatively small load applied to the part.

The first part to be reengineered was the large locking plate that is the element featuring all the constraints for the remaining moving parts.

bad surface finish, insufficient dimensional stability, poor overall performance.

Applied forces generated by the gas piston were causing breakage the part ends because of bad reinforcing fibre orientation and cold weld lines, a well known issue dramatically dropping success ratio also among the best mechanical performing compounds.

For this reason plastic compounds gave no satisfactory results at the beginning of the metal replacement process:

The main reason for these problems had to be found in

FIRST APPROACH: MOULDING ISSUES AND PART FAILURE First steps in project development were guided by the need of maintaining the existing equipment already used to cast metal parts.

The plate was currently moulded by injecting zamak through two wide but thin gates placed along the side of the part cavity.

Geometry, ribs and thicknesses were designed for metal thus no optimization work had been performed because of the

Fig. 3: the feeding system layout

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MKTC001

Copyright Š LATI S.p.A. 2007

12 October 2007 - excellent dimensional stability, even in case of problematic geometries as plates or not stiffened flat surfaces similar to the here discussed part LATIGLOSS 66 is based on polyamide 66 and for this reason processing conditions are much more friendly for moulding machine and equipment because lower pressures and temperatures are required to transform the raw material.

It is evident how lower processing and manufacturing induced costs lead to a more competitive marketing price for the finished products.

MATERIAL CHOICE

Fig. 4: the failure region

Top mechanical performance and outstanding surface finish: two mandatory requirements that can hardly be satisfied at the same time because of the poor aesthetics deriving from glass fibres, often blooming on the surface of reinforced compounds.

This is a very common issue, reducing feasibility of structural parts also supposed to offer a flawless glossy surface.

First trials have been carried out using reinforced aromatic polyamide but a definitive solution has been found in the LATIGLOSS compounds whose formulation provides: - top mechanical properties thanks to the presence of 50 and 60% glass fibres, a reinforcement chosen for specific structural use - perfect surface finish, featuring glossy and homogeneous aspect.

The proprietary matrix formulation provides shiny and bright colours, free of all typical defects due to the high amount of glass or carbon fibres

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MKTC001

Copyright © LATI S.p.A. 2007

12 October 2007

STRUCTURAL ANALYSIS, GEOMETRY OPTIMIZATION

movement is therefore to be considered.

As polymers must be introduced in structural dedicated projects, the first step is to verify if plastic compounds can withstand boundary conditions and applied loads in the course of the whole lifetime.

The plates produced with the zamak mould were not able to withstand even the static trial and the piston broke the shell and the locking bosses because of the momentum generated by its thrust – more than 80 kgs – imposed to the supports.

This passage is fundamental in order to bring improvements directly into the part geometry before the tool is cut.

Finite element simulations correctly identified the weakest

Fig. 5: a complete hinge overview

region as well as the fatal stress amount.

Failure was due to the flexural stress deriving from the piston position rather than from the imposed tensile forces.

The second step was to deeply investigate the plate behavior to creep phenomena generated by internal continuous stresses due to the piston force.

The calculation here discussed has been split into two main branches: 1 – a static evaluation of the capability of the plate to resist to the force developed by the gas piston used to smooth the opening/closing movement of the door 2 – a life-expectancy forecast, based on a ten years period and keeping track of the thrust developed by the piston also when the door is closed and no Fig. 6: structural analysis: loads and constraints

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MKTC001

Copyright Š LATI S.p.A. 2007

12 October 2007

To simulate the applied constraints occurring when the plate is fixed to the piece of furniture, the part has been linked to an ideally rigid surface.

Results showed that, even if the plate might withstand the thrust of the piston, it would bend in a remarkable way within ten years, hence its functional purposes would be strongly reduced.

It was then evident that geometry modifications were necessary to improve the overall performances of the part and FE simulations might confirm immediately whether the taken direction was

Fig. 7: reinforcing ribs layout

correct or not.

All over the 3D geometry adequately positioned and dimensioned ribs have thus been distributed, wall thicknesses have been revised trying to exploit the benefits deriving from strong fibre orientation along useful directions.

Resulting stresses have been vastly reduced with the improved geometry:

Fig. 8: original geometry: creep deformations

Fig. 9: original geometry: stresses

- the overstressed region where breakage occurred turned out into a resistant area where calculated Von Mises stress had been cut by more than 50%, passing from 100 to fairly more than 40 MPa

Fig. 10: modified geometry: stresses

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MKTC001

Copyright Š LATI S.p.A. 2007

12 October 2007 Simulation results confirmed how process requirements of LATIGLOSS materials are similar to those of ordinary glass reinforced polyamide 66 compounds featuring a considerable amount of fibers.

Fig. 11 :modified geometry: creep deformations

Also outstanding surface finish can be obtained by regular mould temperature, i.e. 80-90°C. The calculation showed an easy and complete feasibility of the plate without falling into issues due to remarkable viscosity of the melt polymer and following high melt temperatures needed to fill the cavity, as may occur when PPA and other aromatic polyamides are transformed.

- life expectancy could be satisfied

thanks to a consistent reduction of deformations induced by creep phenomena.

stiffening solutions on the molded part.

It was found how the cause of deformations in molded parts had to be sought in the fiber

Calculated out-of-plane displacements were as small as 0.2 mm after 10 years of continuous use

MOLDFLOW ANALYSIS AND MOULDING PROCESS OPTIMIZATION A structural part like this plate must offer top mechanical performance as well as best planarity.

As foretold, at project startup clearances and tolerance imposed to the finished part had to be obtained by the mean of the already available molding tools.

For this reason LATI performed a complete screening of the molding process by finite element fluiddynamic simulation relying on the Moldflow software.

Injection, packing and consequent deformations on the plate have been studied, carefully evaluating the impact of processing parameters and structural

Fig. 12: fluid-dynamic analysis: fiber orientations

This engineering job provided clear and helpful indications about correct improvements to be applied.

orientation tensor describing local stiffness all over the plate, specially along structural stiffening ribs.

Fig. 13: computer calculated molding warpage

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MKTC001 The simulation turned out into a powerful tool to define adequate solutions consisting into an appropriate review of wall thicknesses and introduction of flow leaders, which were tuned to manage local linear shrinkage values.

Successful molding sessions were achieved thanks to LATI technicians’ survey, whose duty included fine molding machine tuning to obtain the very best out of the LATIGLOSS raw material.

Its improved planarity means better assembly of the plate to the piece of furniture, and easier

Copyright Š LATI S.p.A. 2007 fastening of the leverage system to pins and bosses.

EXTENSION OF METAL REPLACEMENT As the first metal replacement attempt was successfully accomplished, EFFEGI quickly decided to export this winning solution to all the other part of the whole hinge system and metal to plastics conversion is almost total today.

The superb aesthetic aspect of the molded parts and overall outstanding mechanical performance allow EFFEGI to

12 October 2007 implement the LATIGLOSS compounds into both structural parts and covers, without loosing appeal or reliability with their Customers whose expectations can never be let down. Global chemical and thermal performance of LATIGLOSS products push parts performance far beyond the limits imposed by working conditions and life expectancy.

Another exciting example of how a close partnership between enthusiastic designers, material experts and a good engineering team can win the hardest marketing challenges.

Fig. 14: from zamak to thermoplastic compounds

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Copyright Š LATI S.p.A. 2007

12 October 2007 Fig. 15: Computer designed part

EFFEGI BREVETTI Effegi Brevetti was founded in 1964 by Fiorello Giovanetti.

From the beginning our mission has been to supply the furniture industry with unique advanced solutions, in terms of concept and design. These solutions allow diversification and add value to every company’s product range, with the added pleasure of using them.

We design, develop and produce advanced and sound technological solutions in order to solve the most complex of technical problems. Our Research and Development team, are highly skilled and motivated and are very aware of customers requirements, they are able to identify and propose useful solutions.

Every year we continuously offer new products to the marketplace, today more than 30 products have been registered and patented by the company.

In addition we collaborate with some of the best known Italian industrial designers; in fact we believe that a component, or a fastening attachment must combine functionality and style, so that it enhances the design of the furniture.

In early 2007 we launched the EVO part into the marketplace.

EVO has evolved from a clear concept: to realize a design suitable for common applications, aimed at a wider market whilst achieving price stability.

The component has been developed for hanging wall units in high-end kitchens, and also furniture with flap fittings, and vertical and oblique opening doors.

The component located inside the furniture is mounted with one drilled hole for four different types of opening with perfect surface finish integration, even with openings close to each other.

The openings allow an excellent accessibility to the storage areas, due to a lot thought being given to the hinge system which permits lower stress in the opening and locking phases. The locking is also made easier by a piston.

EVO component performance is high even in terms of moving capacity: they are able to move doors that weigh up to 17 kgs.

In order to retain these features and to contain costs, EFFEGI BREVETTI is looking for innovative and different materials to utilise instead of Zamak or castings, which limit surface finish and design aspects.

With an Engineering thermoplastic material, characterised by high mechanical performance and all the advantages of lower cost colour management, we are able to use a product with an outstanding surface finish and uniqueness. One which has been fully used by designers in order to characterize and to add value to different furniture ranges.

The product design group is directed by Studio Paolo Nava Architetto.

Today we are determinedly and coherently carrying on the study and development of new cutting edge application solutions and are continually investing in the growth of our human resources.

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