While stereolithography (SLA) is the oldest of all the 3D printing technologies, it remains the gold standard for overall accuracy, surface finish, and resolution. It uses an ultraviolet laser focused to a small point, drawing on the surface of a liquid thermoset resin. Where it draws, the liquid turns to solid. This is repeated in thin, two-dimensional cross-sections that are layered to form complex three-dimensional parts. Material properties are typically inferior to those of selective laser sintering (SLS), but the surface finish and detail are unmatched.
Selective laser sintering (SLS) uses a CO2 laser that draws onto a hot bed of thermoplastic powder. Where it draws, it lightly sinters the powder into a solid. After each layer, a roller lays a fresh layer of powder on top of the bed and the process repeats. Since SLS uses actual engineering thermoplastics, its 3D-printed parts exhibit greater toughness.
Selective laser melting (SLM) is a specific 3D printing technique, which utilizes high power-density laser to fully melt and fuse metallic powders to produce near net-shape parts with near full density (up to 99.9% relative density).
Multi Jet Fusion MJF is an industrial 3D printing process that produces functional prototypes and end-use production parts develpoed by HP.
FDM stands for Fused Deposition Modeling, alternatively referred to as fused filament fabrication (FFF), is the most common 3D printing technology available on the market. FDM printers operate with extruders that are compatible with thermoplastic filaments.