Stereolithography (SLA) is an additive manufacturing process using a vat of liquid UV-curable photopolymer "resin" and a UV laser to build parts a layer at a time.  To create each layer, the laser traces a part cross-section pattern on the surface of the liquid resin. Exposure to the UV laser light cures, or, solidifies the pattern traced on the resin and adheres it to the layer below.

After a pattern has been traced, the SLA elevator platform descends by a single layer thickness, after which a resin-filled blade sweeps across the part cross section, re-coating it with fresh material. On this new liquid surface, the subsequent layer pattern is traced, adhering to the previous layer. A complete 3D part is formed by this process.

Stereolithography requires the use of support structures to attach the part to the elevator platform and to maintain the integrity of the geometry.  This is done to counteract deflection due to gravity, and to accurately hold the 2-D cross sections in place.  Supports are generated both automatically and manually during the preparation of 3D CAD models.  After building, parts are cleaned of excess resin support structures by immersion in a chemical bath, then cured in a UV oven.