SLS

SLS (selective laser sintering) uses a laser to fuse, layer by layer, a bed of plastic powder, usually nylon PA12 or PA11. Unfused powder supports the part during printing, so there are no supports, and many parts can be nested in the same build volume.

How it works

Because the part grows inside the powder, SLS allows internal channels, print-in-place assemblies and thin walls, with more uniform mechanical properties than FDM. The finish is slightly porous and matte, and can be dyed, blasted or sealed. It is the go-to process for small runs of functional plastic parts without an injection mold.

Practical example

A startup needed 300 enclosures for a field pilot. An injection mold would take months and a large budget. In SLS, the enclosures were printed in a week and dyed black, and changes requested by the first customers went into the next batch with no tooling cost.

Common mistakes

• Designing closed volumes with no hole to remove internal powder.
• Expecting an injection-molded finish without post-processing.
• Using unnecessarily thick walls, which raise cost and warp.