Arrk made a close-up comparison to show resolution and accuracy of the 5 most common Rapid Prototyping technologies in Australia and New Zealand.
FDM - Fused Deposition Modelling:
FDM is a layering process, it uses a filament of actual thermoplastic that is melted and extruded through a tiny nozzle. The nozzle draws the 2D cross-section of the part and then criss-crosses inside to fill in the volume.
The material properties are better than other rapid prototyping processes. However, due to voids and imperfections in interlayer adhesion, it does not match the strength of the base engineering resin. Therefore, if you require engineering prototypes for functional testing, you are better to use Rapid CNC or Rapid Plastic technologies to provide you with more accurate results.
FDM's weakness is resolution and accuracy of small features. This is primarily why Arrk does not offer it as a service.
Objet 3D printing:
Objet 3D printing is a newcomer to the rapid prototyping industry. However, it is gaining ground rapidly for concept modelling applications. Objet 3D printing uses multiple jets to deposit UV-curable liquid in remarkably thin layer thickness, which gives the models great Z axis resolution.
Objet 3D printing’s strength is its ability to reproduce fine detail definition and its wide range of hard and soft rubber-like materials, with a medical and food-grade material option.
Objet 3D printing weakness is that these materials are functionally limited and not suitable for high impact or heat testing.
SLS - Selective Laser Sintering:
SLS has been in existence for many years. Selective Laser Sintering builds models layer-by-layer with a bed of thermoplastic powder. Each layer of fresh powder is sintered (slightly melted) together using a high-power laser. Then a fresh layer of powder is rolled onto the surface so that the process can be repeated for the next cross-section.
Selective Laser Sintering (SLS) parts are typically strong and exhibit material properties that come close to the base material. They are an good choice for parts requiring strength and toughness, and can be used in high temperature tests. The weakness of SLS is its inability to do fine details and its coarse surface finish.
SLA - Stereolithography Apparatus:
SLA technology uses an optical configuration, with a UV laser solidifying epoxy liquid layer-by-layer. This process is suitable for both small, detailed parts or large parts, with machines available containing build platforms up to 1800x800x800mm in size.
Stereolithography Apparatus (SLA) technology has been around for a long time and consequently a lot of time and money has been spent in improving the mechanics of the material.
Whilst the flexural strength of SLA material has improved, SLA prototypes still have limited functionality and not suitable for high temperatures or impact tests.
Z-Corp is a 3D printer for concept modelling. The print heads jet out a binder onto a bed of powder in multiple layers to form 3D parts. One unique feature of some Z-Corp machines is their ability to make multi-coloured parts directly in the machine using coloured binders.
The materials used are starch based and once the model is built they are dipped into a glue to strengthen the surface. Despite this, the parts remain fairly fragile and thin wall-sections easily crumble and break.