SLS stands for selective laser sintering, a process patented by Carl Deckard in 1989 and a trademark of 3D Systems, which acquired the DTM Corporation of Austin, TX, and the SLS process in 2001. This is a process where a laser traces a beam onto the surface of a container of fusible powder. The laser heats the particles of powder and sinters them together into a solid section. An elevator drops by a small increment and another layer is sintered to the preceding layer. The process builds in layers, similar to stereolithography, except using dry powder instead of liquid polymer as a medium. The SLS process does not require the use of support structures as in stereolithography and FDM, as the part is supported by the uncured powder material as it is lowered into the powder chamber.

One advantage to the SLS process is its versatility. Almost any material that can be powdered and sintered may be used to produce a part. Parts made from sintered nylon, for example, are quite tough and flexible. SLS process build materials include glass-filled rigid plastics, elastomers, and metals. Since the SLS process allows the fabrication of sintered elastomers, making prototypes of rubber parts such as shoe soles and custom-shaped orthopedic brace padding is possible.

Another use of the SLS process is the production of injection mold tooling and tooling inserts. The SLS process allows the production of injection mold tools with built-in conformal cooling channels.

Another example for the SLS process in medical device design is fabrication of sintered metal parts such as laparoscopic grasper jaws that model the characteristics of powdered metal injection molded (MIM) parts. As-built SLS metal parts are green and require postcuring in a special oven to achieve full strength and density. SLS powdered metal parts may be infiltrated with bronze to increase strength and density and eliminate porosity.

SLS is an RP technology requiring specialized capital equipment and skilled operators. It is best to utilize this technology through a service bureau. The 3D Systems website provides links to a number of qualified service bureaus offering SLS part-building services.

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