Stereolithography, or STL, is an additive technology which uses a UV laser to create parts from a UV curable liquid within an SLA, or Stereolithography Apparatus, system.

For a part to be created using STL, a 3D model of the desired part must first be created, after which the 3D data is seperated into a group of 2d layers of the entire part. These layers typically range from 0.10mm to 0.050mm in thickness (although a resolution of 0.050mm in thickness is usually used) and this group layers is called called "slice data." The slice data is then fed into the SLA system and the actual fabrication process begins. The platform is first lowered into the vat of clear, liquid plastic photopolymer. The polymer used is sensitive to ultraviolet light, allowing the polymer to solidify when it is exposed to the light provided by the UV laser and the materials used in this process range from soft durable plastic to hard plastics. The ultraviolet laser traces and selectively solidifies the first layer within the resin onto the platform, which is currently submerged one layer under the resin. http://cadmodels.org/?q=Stereolithography