By guest author Bridget Butler O’Neal from 3D Print Board
Designer Mark Beecroft of the Manchester Metropolitan University School of Art has been exploring the potential of 3D printing in industrial knitting in his recently published paper, ‘Digital interlooping: 3D printing of weft-knitted textile-based tubular structures using selective laser sintering of nylon powder.’
The technology of 3D printing is perfectly suited to this type of textiles manufacturing, and specifically, using selective laser sintering (SLS) in the fabrication of tubular forms of varying sizes. The use of 3D printing is also appropriate for the production of apparel as the technology has lent so much already to the bold realm of fashion, from dresses to bathing suits to shoes.
With the accompaniment of CAD-based programs, knitting manufacturers can easily create interloping structures that loop and extend with the proper elasticity.
“By 3D printing knit-based structures it’s possible to embed knit’s inherent properties of stretch and flexibility, whilst exploiting the mechanical properties of the material used to print with,” states Beecroft.
While previous research into 3D printing knitting structures has been performed, it mainly pertained to non-continuous, linked geometries. Here, Beecroft examines the use of 3D printing continuous fiber type geometries and testing resulting structures that are both single- and double-face. Evaluation of each structure includes checking how well they handle being compressed and extended, along with total flexibility.
SLS with nylon has historically been known as an excellent combination, resulting in:
- Good mechanical properties
- Good flexibility
- Good labelling quality
- Good detail
Some SLS printers (but not the one used in the experiment) can also handle polyurethane plastics (TPU) well—notably exemplified in 3D fashions by Iris van Herpen and Julia Koerner.
The knit structures studied by Beecroft were 3D printed on an EOS Formiga P110, with Nylon PA12 as the selected material, requiring no extra supports apart from loose powder, and offering the required stability and strength.
“Once printed each of the tubes were tested to determine their compressed and extended length, this was achieved by compressing each of the tubes by hand to the minimum length without deformation of the loops and recording the measurement,” states Beecroft. “Each tube was then extended by hand to the maximum length without deformation of the loops this measurement was then recorded.”
“Following this, each tube was tested for stretch capability by manually stretching each tube over a cardboard cone structure with a minimum diameter of 25 cm and a maximum diameter of 55 cm. The stretching over the cone was repeated 10 times to test stretch and recovery properties of each tube. Finally, each tube was manually manipulated by bending and folding by hand to test for overall flexibility and ability to return back to original form.”
The structures showed good recovery after compression, along with the proper flexibility (We would be curious to see how long this property will last). Beecroft was encouraged by the study, stating that it shows the potential for 3D printed tubular knit structures.
“However, a limitation of this research is the lack of standards or defined test procedures suitable for testing 3D printed textile-based structures,” concluded Beecroft. “The author is planning to carry out further research to test the durability of these printed structures in a controlled laboratory environment to test tensile strength, elongation and load to the breaking point.”
“This research has shown that SLS is a suitable manufacturing process to achieve flexible tubular knit-based structures using Nylon (PA12) powder. Further research into other flexible powder material such as TPU would be of interest to test the mechanical behaviour of the material, in combination with the knitted structure’s inherent properties of stretch and flexibility. This would enable a comparative study to be made between Nylon (PA12) and TPU.”