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 stereolithography model is
then finished by smoothing the "stair-steps."