SLS 3D printing

SLS 3D printing (selective laser sintering) is a powder bed additive process in which a laser sinters plastic powder, most often polyamide PA12 or PA11 (nylon 12 or nylon 11), layer by layer. The unsintered powder acts as a natural support, so even very complex geometries can be printed without support structures.

The biggest strength of SLS printing is the mechanical properties of the finished parts, which come close to those of injection molded parts made from a similar material. The parts are tough, heat resistant and, compared with FDM printing, much less anisotropic (their properties are similar in all directions, though not identical). That makes SLS a good choice for functional prototypes and for parts where mechanical durability matters.

SLS printing suits mechanically loaded functional prototypes, parts with complex internal channels or lattice structures, small batches of production parts, and fast production without investing in a mold.

The surface of SLS parts is matte and slightly porous. It can be further treated by bead blasting, dyeing or chemical vapor smoothing, which improves appearance, cleanability and, to some extent, mechanical properties. The technology costs more than FDM or SLA, but the parts are mechanically more robust.

SLS is a good fit for functional prototypes that have to withstand real loads: snap fits, clips, housings, brackets, air ducts, or assemblies with moving parts printed in one piece. Because no supports are needed, it also handles geometrically complex parts with internal cavities well.

Another common use is low-volume production of tens to hundreds of parts, where an injection mold does not pay off yet, or bridge production until the mold is ready. The build volume can be filled with many parts at once, which lowers the cost per part.

SLS parts have a rougher, porous surface that absorbs dirt and liquids. Watertight or food-contact applications require additional treatment and verification. Thick, solid sections can warp and shrink, so it is better to design walls of uniform thickness (typically around 1 to 3 mm) and to hollow out bulky volumes.

Enclosed cavities need escape holes so the powder can be removed; otherwise it stays trapped inside. For moving joints printed in one piece, allow a clearance of at least a few tenths of a millimeter. Ask your supplier about the specific material (PA12, PA11, filled grades), color, surface finish and the achievable accuracy for the given part size.