What are the Different Types of Rapid Prototyping?
Stereolithography (SLA) or Vat Photopolymerization
This fast and affordable technique was the first successful method of commercial 3D printing. It uses a bath of photosensitive liquid which is solidified layer-by-layer using a computer-controlled ultra violet (UV) light.
Selective Laser Sintering (SLS)
Used for both metal and plastic prototyping, SLS uses a powder bed to build a prototype one layer at a time using a laser to heat and sinter the powdered material. However, the strength of the parts is not as good as with SLA, while the surface of the finished product is usually rough and may require secondary work to finish it.
Fused Deposition Modelling (FDM) or Material Jetting
This inexpensive, easy-to-use process can be found in most non-industrial desktop 3D printers. It uses a spool of thermoplastic filament which is melted inside a printing nozzle barrel before the resulting liquid plastic is laid down layer-by-layer according to a computer deposition program. While the early results generally had poor resolution and were weak, this process is improving rapidly and is fast and cheap, making it ideal for product development.
Selective Laser Melting (SLM) or Powder Bed Fusion
Often known as powder bed fusion, this process is favoured for making high-strength, complex parts. Selective Laser Melting is frequently used by the aerospace, automotive, defence and medical industries. This powder bed based fusion process uses a fine metal powder which is melted in a layer by layer manner to build either prototype or production parts using a high-powered laser or electron beam. Common SLM materials used in RP include titanium, aluminium, stainless steel and cobalt chrome alloys.
Laminated Object Manufacturing (LOM) or Sheet Lamination
This inexpensive process is less sophisticated than SLM or SLS, but it does not require specially controlled conditions. LOM builds up a series of thin laminates that have been accurately cut with laser beams or another cutting device to create the CAD pattern design. Each layer is delivered and bonded on top of the previous one until the part is complete.
Digital Light Processing (DLP)
Similar to SLA, this technique also uses the polymerisation of resins which are cured using a more conventional light source than with SLA. While faster and cheaper than SLA, DLP often requires the use of support structures and post-build curing.
An alternative version of this is Continuous Liquid Interface Production (CLIP), whereby the part is continuously pulled from a vat, without the use of layers. As the part is pulled from the vat it crosses a light barrier that alters its configuration to create the desired cross-sectional pattern on the plastic.
Binder Jetting
This technique allows for one or many parts to be printed at one time, although the parts produced are not as strong as those created using SLS. Binder Jetting uses a powder bed onto which nozzles spray micro-fine droplets of a liquid to bond the powder particles together to form a layer of the part.
Each layer may then compacted by a roller before the next layer of powder is laid down and the process begins again. When complete the part may be cured in an oven to burn off the binding agent and fuse the powder into a coherent part.
Applications
Product designers use this process for rapid manufacturing of representative prototype parts. This can aid visualisation, design and development of the manufacturing process ahead of mass production.
Originally, rapid prototyping was used to create parts and scale models for the automotive industry although it has since been taken up by a wide range of applications, across multiple industries such as medical and aerospace.
Rapid tooling is another application of RP, whereby a part, such as an injection mould plug or ultrasound sensor wedge, is made and used as a tool in another process.