Knitectonics
Chapter IV
Digital Machine
digital machine
Our digital explorations began with simulation of the knitting action and fabric behavior, which eventually became our primary design tool. In the initial phase of digital simulation, our decoding system could simulate different yarn with varying properties, openings, different patterns and solidification, under the effect of gravity and time. Our first prototype of the machine, the rectilinear machine, helped us to speculate the real scale deployment of the system, but the simulation was primarily focused on fabric behavior and patterning and not on the machine itself. After conceptualizing the hexagonal machine (a physical prototype of which was not feasible), to explore systemic aspects and topological complexity it became imperative to construct a digital machine. The challenge was to create a simulation system that digitally imitate all parts of the machine and their actions, which together would create a knitted structure. The parts of the machine executing different functions were split into tasks in the simulation system, such as the tracks, the yarn feeder and the bridge connections. These were digitally developed individually and later combined together to form the complete system. We scripted the simulation in Java language (since it is object oriented) using an open source software ‘Processing’. For simulation of physics (environment, particles, springs) an additional library ‘Toxiclibs’ by Karsten Schmidt was used.
Machine Prototype Detail
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Knitectonics System Anatomy Needle The needle is the smallest performing component of our mechanic system. It inter loops the yarn to create the knitted fabric, while holding the knot for inter looping the next set of knots. The needle thus holds the fabric and releasing of this knot creates holes in the fabric. Bed of Needles The Bed of Needles is a segment of the track, which is a support base for the needles. Each bed has a certain number of needles and a “bridge� at the beginning of it. Bridges The bridge is a point where beds of a certain tracks are linked. These also become the connection points with other tracks. Track The track is a combination of six needle beds and its needles and it carries the information required to create a specific machine i.e. the radius, total number of needles and position. These parameters then determine the specifics of the bed and the needles. Each track has six beds and thus six bridges, every 60 degrees, which connect to other tracks. Knitting Action The knitting process on a physical knitting machine involves each needle to create a loop. This loop is retained until the yarn interloops to create a new loop, following which it is dropped to create
Track T0 Bed B0 B1 B2 B3 B4 B5
Bridge point
Bed
Needles
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Bridge Br0 Br1 Br2 Br3 Br4 Br5 Needle n0 n1 n2 n3 n4 n5
digital machine
the fabric. So each knot is singularly active on the needle and once it is off the needle as a part of the fabric, it is under collective action. In the simulation, each knot on the needle is represented by a ‘particle’. These ‘particles’ are then dropped just like the knots and the resultant fabric can be described as a ‘number of particles’ connected with ‘springs’, which are the digital equivalent of the yarn. Knitted Fabric Each yarn used in knitting has specific properties and it was imperative to embed this data into the simulation to get a real picture of the material behavior. As the knitted fabric falls with gravity and so the behavior of the yarns governs the behavior of the fabric. So apart from the colour, in the simulation script each yarn was imparted the following characteristics. Physics The knots of the fabric are represented by ‘springs’ from the physics library of ‘Toxiclibs’. These ‘springs’ are subjected to forces of gravity and other springs around them, as the knots are relational and impact each other. Yarn Strength The yarns are differentiated by the strength of the ‘spring’ of each yarn. Spring strength is defined in a range of maximum stretch and maximum compress and has an ideal rest position, such that the springs under all forces are always attempting to come to that rest position. Yarn Weight As the force applied on an object in the product of its mass and the gravitational acceleration, to calculate the force on the yarn this information is required. The gravity is declared as a global variable in the script and weight of each yarn is established in yarn properties. Digital Interface Track 01 Video Controls Activation
Settings Display Head Functions Yarn Functions Solidification Files Export
Controls Movement Speed
Fabric H1
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Knitting Head 1
Knitectonics
Knitted fabric before attachment
Fabric attached to the ground
Tension difference created by variation of speed of movement
Machine Dynamics In conventional knitting, the machine is stationary and the knitted fabric is pressed under rollers and pulled down. In our conceptual machine, the machine moves up while knitting and gravity and ground are utilized to attach and tense the fabric. The following functions are used for simulating real time dynamics of the system. Fabric Attachment This function allows us to attach the fabric to the ground or any other horizontal plane and the distance after which it attaches can be set on the interface. Here the first row of ‘particles’ on the needles of the machine are attached to corresponding attachment points on the attachment plane. Machine Movement This operation enables us to move the machine vertically upwards. The movement speed can be adjusted as per the tension required; a tight knit fabric would require a high speed whereas at a slow speed the knit would be loose. Tension Tension is an absolute necessity for analogue knitting and is done by using weights and rollers in machine. In the digital system, the tension derived is a combination of machine movement speed and the friction caused by the attachment plane. 99
digital machine
Model in process of solidification (blue segment)
Materiality In our analogue experiments, we studied the implications of knitting multiple yarns simultaneously. Being in the realm of fiber composites, matrix materials for solidifying the yarns were used and eventually, we explored the possibility of the fiber and matrix combination in a single material i.e. the pre-impregnated yarn. These were integrated into the simulation also. Multiple Yarns Each single yarn had selected properties: color, rest position, weight, strength etc. For combining multiple materials, the simulation creates a new material with a distinctive identity and colour and combines the rest position, weight and strength of all the different yarns used. Solidification This function imitates the machine and instigates the process of solidification of the yarn after it has been knit. The time between the knitting and solidification can be regulated on the interface. For solidifying a knot, the simulation freezes the springs of the ‘particles’ involved. Pre-Impregnated Yarn
Model with 3 different yarn materials
The knitted fabric can be soft and rigid, hence our digital system also needed the flexibility to selectively solidify a specific yarn and not all yarns like the solidification function. This way the simulation takes into account the structural pre- impregnated yarns. 100
Knitectonics
Two Tracks To understand the bridge function, we consider the minimal setup of two machines. The yarn heads carry the yarn and drop particles and springs along the track. The two tracks can be isolated, with two yarn heads knitting two tubes. On introducing the bridge function, the yarn head can move from one track to another. The bridge activation and routine can be predefined on the script or can be modified in real time on the interface. With two machines, the yarn head can either bridge to knit a larger perimeter or cross- bridge to knit and stitch two tubes together. Routines of bridge activation – deactivation and bridge- cross bridge, facilitate us in creating connections, bifurcations and topologies. 101
digital machine
Head Sequences
Sequence 0
Sequence 1
Sequence 2
Sequence 3
Further improvements in the machine design led us to the deduction, that the bridge was not required as a physical element; but rather as an action of the yarn head. At any connection point of two tracks in the hexagonal circle packing grid, the yarn head could perform any of the four prescribed actions. We refer to these actions as ‘sequences’. Sequence 0: The ‘sequence 0’ is a command for the yarn head to bypass a connection point. Sequence 1: The ‘sequence 1’ is a command for the yarn head to return back from a connection point. Sequence 2: The ‘sequence 2’ is a command for the yarn head to bridge across a connection point. Sequence 3: The ‘sequence 3’ is a command for the yarn head to cross- bridge at a connection point. It is important to note here, that the ‘connection point’ connect two needles on one track, to corresponding two needles on the other track. So in sequence 2, the yarn head bridges two needles located in parallel, to give a larger perimeter as a result. Whereas in sequence 3, the yarn head bridges across two needles located in diagonal and stitches the two cylinders together. Each yarn head can hence be prescribed a routine of ‘n’ number of sequences and this routine can then repeat endlessly. We added another command ‘sequence 9’ as a void function, which can be put in a routine to instruct the yarn head to move to the next sequence function. 102
Knitectonics Three Tracks
Track has been drop (See red dots above)
The complexity of the digital system is augmented as the number of tracks increases. Certain system operations can be best demonstrated with multiple numbers of tracks. For example the implications of the initiation point of the heads, dropping of needles of a track, needle bed and bridge, using different segment locations of the tracks, attachment control and lastly exploring the topologies created by multiple configuration of tracks. Head Starting Point In this configuration there is an external perimeter and an internal perimeter, enclosed within the three tracks. The starting point of the yarn head on the external perimeter versus the internal perimeter, can yield diverse results. As the yarn head path is prescribed by the routine of sequences, the knitted outcome is specific to the initiation point in the configuration of tracks. Dropping Knots From our analogue machine experiments we knew that the knit density can be changed and holes can be created by dropping of knots from the needles. The idea of the digital machine is to experiment with topology and openings at an appreciable scale, so we focused on dropping knots not for single needles, but for a group of needles. The simulation system gives us the possibility of dropping a whole track or a certain needle bed of the track or just the bridge, as per the design prerequisite. On the tab ‘track functions’ of the interface, the drop track, bed or bridge function can be activated. The slider then enables us to locate and preview the track, bed or the bridge to be dropped. 103
digital machine
Variable Perimeters As mentioned earlier, there is an external perimeter and an internal perimeter enclosed within the tracks in a hexagonal grid. These perimeters- the track itself (large perimeter) and the interstices created (small perimeter) can both be employed as paths for the yarn heads. Interestingly, the speed of machine movement becomes critical here as each cycle of the larger perimeter takes five times the time required to complete a knitting cycle on the smaller perimeter, either causing the knit on the inside to be very loose or the knit on the outside to be very tense. This can be countered by increasing the number of heads on the larger perimeter. The interstices give the opportunity to vary the enclosed knitted volumes and could help us create structural elements, sub divisions or shafts. Attachment control Along with all the above functions in the digital system, the option to attach or not attach at any specific moment and the possibility to attach to the ground or another horizontal plane, opens up a new domain of topologies and morphologies. For instance, knitting on a track for a certain height and attaching it to the ground plane gives us a simple tube. But after that height, if more tracks are added to increase the perimeter without attaching them to a horizontal plane and moving the tracks vertically at a reasonable speed, we can achieve cantilevers with interesting cross sections. Thus, facilitating us to realize most of the tasks dealt with conventional materials and machines in architecture. 104
Knitectonics
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Frozen Fibers S a n h i t a C h a t u r v e d i [India] E s t e b a n C o l m e n a r e s [Colombia] T h i a g o M u n d i m [Brazil]
Tutors
Marta MalĂŠ-Alemany Jeroen van Ameijde Daniel Piker
www.knitectonics.com
Machinic Control 2.0 Design Research Lab v13 Archit ectural Association London Phase II Copyright Š Frozen Fibers 2011, otherwise indicated and used only for academic purposes.