Three dimensional (3-D) printing, potential footwear applications and Materials

3-D  printing

Three dimensional (3-D)  printing is one of the cornerstones of modern 'additive' manufacturing processes  where an object is formed through the successive addition of  just enough material to make  it. Additive processes are those that join  materials to make an object as with the  layers of 3D printing rather  than the subtractive  processes of traditional  machining  using lathe, mill and drill  which  removes material. A worker  starts with a large  piece of material ( perhaps leather, wood or metal ) out of which the cuts drills or curves a much smaller product. He discards  the excess material  that is removed, most  of which may never be reused. Additive processes allow a product which exists only  as a CAD or data file on a computer to be output directly to a  machine that will  form the item entirely automatically and  with minimal waste.

3D printing technology

All 3D printing uses an additive process. The difference between  thee most common  technologies used in the industry are how the  layers are built. Essentially, there  are four main types of additive manufacturing  that  fall under the umbrella term  3D printing..

1. selective  laser sintering ( SLS)
2. Fused deposition modeling ( FDM)
3. inkjet 3-D
4. Stereslithography (SLA)

Applications

Three dimensional printers help designers, developers  and researches as their  ideas can be made into  digital designs and  then printed in a short time. If  adjustments  are needed designs  can be easily changed and then reprinted three dimensional printers can also  be used  to  print new  replica parts for machines or a specialized part  required to  adopt  a  current machines to a customers specific needs. The use of 3D printing is finding applications in  many aspects of  lie  such as  art, architecture, fashion design, interior design, engineering and prosthetic production etc.

potential  footwear applications

3D printing technology  is already  used to create viable prototypes  of new designs SLS and 3D inkjet printing  can both be used to  create durable (but non flexible) prototypes  that can be passed around at a  design meeting to  view  the aesthetics, colors and style  of  a  shoe complete  in every detail.

Previously, these concept shoes would have been either a simple drawing or a slow and carefully made  model. It  is easy to realize the savings in  both  time and effort and  the advantage of having a three dimensional and  tangible item that can be handled and assessed .

Models can be produced in a wide range  of colors  and materials of different  texture can  be simulated using the high  resolution of 3D printing  materials to recreate the wave and  stitching of various  fabrics.. 

It is now even possible create models that can be tentatively checked for fit the limitations or a full assessment being the  rigidity of the material which  be  affect the comfortable ingress of the foot.

While it is possible to create a model of any type of  shoe, particularly suit the production of  rigid  or stiff soled footwear - such as women's high -heeled shoes and student football boots. when rigid footwear is modelled, the printed results looks, fits behaves almost exactly like the production footwear, albeit  it is more brittle and less durable.

Footwear that  will  be flexible when commercially  produced can be modelled using these 3D printing methods in very  intricate detail right down  to stitching detail and apparent creases in the  reproduction fabric, but will  not  flex  or move like the real thing. 

This opens up  to designers the possibility of creating unique innovative  footwear  with designs  so intricate  as to preclude  their  manufacture by conventional means. These  shoes could  be  both handled  and  warn even if  they survive only one or  two journeys up and down  the catwalk. Some methods can create soft  and flexible models that  represent soling material, as well as  whole  shoes constructed from  rubbery or pliable  material.

It is surely will not be to long before complete shoes can be printed  especially  something simple such as  a one piece, moulded  type of footwear. This concept of footwear on demand is appealing to many and is likely to be one that has great commercially value. Customers could have their feet sent to a 3D printer that creates their exact size, taking into account he unique physical  characteristics of  their foot. This access  to  perfectly tailored footwear  could mean a big improvement in performance  particularly for those  involved in sports.  such an improvement could especially  be seen if he materials used in the  printing process  could be customized  to produce a level of flexibility that perfectly suited  the weavers and their chosen  sports.

Materials

In 3D printing, there  are many  materials can be used. The  most commonly used materials are as follows:

a) General purpose plastics which are  affordable  durable and easily available for  example acrylonitrile butadiene - styrene (ABS) and polylactic acid (polylactide)  know  as PLA.

b) high detail  resin  which can  be used to produce intricate and detailed designs with a smooth surface finish. 

c) SLS nylon used to make functional prototype from lasted sintered  nylon.

d) Fibre reinforced resin for engineering parts said to be as strong as  metal but at  the price of plastic. 

e) rigid opaque plastic, to  make realistic prototype with  high detail and accuracy.  

f) Transparent plastic from which see through  part can be printed.

g) Engineered polypropylene  used to make durable prototype  that behave  and look like polypropylene.

h) Engineered ABS, for high precision  designs and injection moulds  with the toughness  of ABS.

i) heat resistant plastics, with  thermal resistant  prototypes  up to 80^o C.

k) Industrial  metals  include  graphene , carbon fibre, silicon, regolith, wood, glass, nylon,  paper and cement polymer.

Advantages and disadvantages:

There  are clean  and definite benefits resulting from the use of 3D printing methods  than traditional subtractive technologies. It is important  to  lander stand that 3D printing is  still a  developing technology. As such it  comes with  benefits, but it  is still not at the level to take over from traditional  footwear  manufacturing methods. 

Thee  advantages  of 3D printing are that  complex  design can be created without tools or  moulds, which produces less waste. Designs can be customized and seen as  physical prototype  within a couple of  hours due  to the rapid  speed of 3d printing.

However,, there are some drawbacks to  using  3D printing. Although there  are many materials available  to use  the choices are still limited compared  to conventional product materials colors and finishes.  The material also have a limited amount of strength and the process  offers a lower level of precision. The main disadvantage  is having higher costs for large production. This will improve as  the price of  pinners  an  raw materials  continues to  decrease while  at the same time thee  range of  efficient production expected to increase.

1. Selective Laser Sintering (SLS)

In the selective laser sintering process, a digital CAD file output to a machine.. This directs a laser beam to  move backwards and forwards over the surface of a bed of powder, fusing it into a solid  form where it is hit by the laser. This process  is  repeated layer  by layer with the  powder bed being lowered by a fraction of millimeter after each  layer is fused  the  fresh powder deposited  on  to and  leveled by a sliding blade. 

The  advantage of  the SLS  process  is that the item being created is both supported and  increased  by the bed of powder enabling shapes  of highly complex geometry  to be produced. SLS forms  rigid, hard  structures which are  released  from the  powder bed at  the end of  the process.  Unused powder  is sifted and returned to the machine ready for the next batch of  products  to be made.

As the  technology develops,  an increasing  variety of powdered  substances  are becoming available for use in SLS machines, in addition to  the most  commonly used plastic materials.

2. Fused deposition modeling (FDM)

Thee process that  most people associated with the term 3D printing is used deposition modeling. FDM machines deposit from a heated nozzle  a  liquefied thermoplastic material that  hardens almost immediately after extension. A micro-controllable gantry or work  platform on  which the end probe is formed is moved back add forth relative to the position of the dispensing nozzle, so that an object can  be formed by the gradual building up of layers  of material. A high-level of precision is possible  allowing for creation of very delicate shaped, as each layer can be as fine as 0.05 mm.