FDM 3D printing is a technology that works both horizontally and vertically, where an extrusion nozzle moves over a build platform. The process involves the use of thermoplastic material that reaches melting point and is then forced out, to create a 3D object layer by layer.
Stereolithography (SLA or SL) also known as stereolithography apparatus, optical fabrication, photo-solidification, or resin printing) is a form of 3D printing technology used for creating models, prototypes, patterns, and production parts in a layer by layer fashion using photochemical processes by which light causes chemical monomers and oligomers to cross-link together to form polymers.
Selective laser sintering (SLS) is an additive manufacturing (AM) technique that uses a laser as the power source to sinter powdered material (typically nylon or polyamide), aiming the laser automatically at points in space defined by a 3D model, binding the material together to create a solid structure.
Electron Beam Melting, like SLS and DMLS, belongs to the powder bed fusion family. However, in contrast to other metal AM technologies, which use a laser as their heat source, EBM uses a high-power electron beam to melt layers of metal powder. The melted layers of metal powder are then fused together to create a metal part.