Selective Laser Sintering (SLS)

Selective Laser Sintering (SLS) 3D prints durable thermoplastic parts from powder with no support structures, enabling complex geometries and functional prototypes at low volumes.

Overview

Selective Laser Sintering (SLS) is a powder-bed 3D printing process that uses a laser to fuse thermoplastic powder layer-by-layer. The surrounding unfused powder supports the part during the build, so complex internal features, lattices, and assemblies with moving clearances are practical without support removal.

Choose SLS for functional prototypes and low-volume production parts where strength, heat resistance, and geometric freedom matter more than cosmetics. It’s common for nylon housings, brackets, clips, ducts, and snap features.

Tradeoffs: surfaces are matte/grainy and usually need bead blasting, dye, or coating for appearance; fine details and sharp edges can soften; thin walls can warp; dimensional variation depends on orientation and packing density. Tolerances are good for plastic additive but often require secondary machining for precision bores, sealing faces, and tight fits.

Common Materials

  • PA12
  • PA11
  • PA12 GF
  • PA12 CF
  • TPU

Tolerances

±0.010 in (±0.25 mm) or ±0.3% (whichever is greater)

Applications

  • Functional nylon housings and enclosures
  • Snap-fit clips and latches
  • Ducting and airflow manifolds
  • Custom brackets and sensor mounts
  • Low-volume end-use jigs and fixtures
  • Medical device prototypes (non-implant)

When to Choose Selective Laser Sintering (SLS)

SLS fits complex plastic parts that need real mechanical performance and don’t justify tooling. It works well for one-offs through hundreds of parts where nesting many parts per build keeps cost reasonable. Expect to post-process for appearance and to machine critical datums, bores, and sealing features when required.

vs Fused Deposition Modeling (FDM)

Choose SLS when you need more isotropic mechanical properties, no support-structure scars, and better feature consistency across many parts in a build. SLS is typically better for snap-fits, thin features, and nested builds; FDM often wins on lowest-cost large simple parts and fastest single-off prints.

vs Stereolithography (SLA)

Choose SLS when the part must behave like an engineering thermoplastic (impact resistance, fatigue, functional clips) rather than a brittle photopolymer. SLA wins for smooth surfaces, fine cosmetic detail, and thin-walled visual models; SLS wins for durable, production-like nylon parts.

vs Multi Jet Fusion (MJF)

Choose SLS when you need broader material options, proven nylon performance, and robust builds for complex geometries without tuning to a specific machine ecosystem. MJF often delivers faster throughput, slightly better feature definition, and more uniform gray parts at similar volumes; SLS is a strong choice when material selection or supplier flexibility drives the decision.

vs Digital Light Processing (DLP)

Choose SLS for tough, functional nylon parts and assemblies where powder support enables complex shapes without supports. DLP is better for very fine features and smooth surfaces in photopolymers, but those materials typically trade off ductility and long-term stability versus SLS nylons.

vs PolyJet

Choose SLS for mechanically robust parts and real-world handling without worry about softening or creep typical of some photopolymers. PolyJet is better for high-fidelity cosmetics, smooth surfaces, and multi-material/overmold-like prototypes; SLS is better for durable end-use nylon geometry.

Design Considerations

  • Hold cosmetic expectations: plan for bead blasting/dye/coating, and avoid specifying glossy finishes without secondary processing
  • Keep walls uniform where possible; thin-to-thick transitions drive warp and dimensional drift
  • Add machining stock on precision bores, bearing seats, and sealing faces if tight fits are required
  • Design self-supporting powder escape paths for enclosed volumes; add drain holes and avoid trapped powder cavities
  • Use generous radii and avoid knife edges; sharp features soften and chip during depowdering
  • Define critical datums and measurement scheme on the drawing; quote accuracy improves when inspection surfaces are clear