Stereolithography

Stereolithography (SLA) is often considered the pioneer of the Rapid Prototyping industry with the first commercial system introduced in 1988 by 3D Systems. The system consists of an Ultra-Violet Laser, a vat of photo-curable liquid resin, and a controlling system.
 

A platform is lowered into the resin (via an elevator system), such that the surface of the platform is a layer-thickness below the surface of the resin. The laser beam then traces the boundaries and fills in a two-dimensional cross section of the model, solidifying the resin wherever it touches. Once a layer is complete, the platform descends a layer thickness, resin flows over the first layer, and the next layer is built. This process continues until the model is complete.
 

Once the model is complete, the platform rises out of the vat and the excess resin is drained. The model is then removed from the platform, washed of excess resin, and then placed in a UV oven for a final curing. The model is then finished by smoothing the "stair-steps."
 

Resolution
Standard SLA parts are manufactured using the standard layer resolution of .005".   High Resolution parts, parts with very small features and details, are manufactured using a layer resolution of .002", and a high-res laser spot size of .003".

Materials
The materials used by SLA equipment are epoxy-based resins that offer strong, durable, and accurate models. It is ideal for form, fit, and function testing as well as for visual aids and patterns for tooling. In many cases, SLA is capable of reproducing snap fits. In general SLA materials have a low heat tolerance with typical heat deflection temperatures are around 110-120ºF. Standard tolerances are ± 0.005" for the first inch, and ± 0.002" in/in on most parts and features. These characteristics make SLA an excellent all-round choice for prototypes.

SLA Material Properties