Selective Laser Sintering (SLS)

Selective Laser Sintering fuses nylon powder into strong, support-free 3D parts with complex geometry, good mechanical properties, and medium-level dimensional accuracy.

Overview

Selective Laser Sintering (SLS) is a powder-bed 3D printing process that uses a laser to fuse layers of thermoplastic powder, usually nylon. The surrounding unfused powder supports the part during printing, so you can design complex geometries, internal channels, lattices, and nested assemblies without support structures. Parts are typically strong, isotropic enough for real functional testing, and suitable for many end-use applications.

Use SLS when you need durable plastic parts, complex shapes, and batch production from a few to a few hundred pieces. It excels at snap fits, living hinges, and assemblies with built-in clearances. Tradeoffs: surfaces are matte and slightly grainy, fine details and tolerances are not as tight as some resin processes, and very thick or large flat sections can warp if not designed well. If you can live with moderate tolerances and cosmetic limitations, SLS is a reliable way to get robust plastic parts quickly with minimal DFM constraints.

Common Materials

  • Nylon 12 (PA12)
  • Nylon 11 (PA11)
  • Glass-filled Nylon
  • Carbon-filled Nylon
  • TPU elastomer

Tolerances

±0.3% (±0.010" minimum)

Applications

  • Functional plastic prototypes
  • Snap-fit housings and enclosures
  • Complex ducting and manifolds
  • Wearable and orthopedic braces
  • Jigs, fixtures, and assembly aids
  • Short-run end-use plastic parts

When to Choose Selective Laser Sintering (SLS)

Choose SLS for strong, functional plastic parts with complex geometry, internal channels, and no need for support structures. It fits low- to mid-volume runs (prototypes through hundreds of parts) where nylon-like properties matter more than fine cosmetics or very tight tolerances. SLS works well when you want assemblies printed in one build and can accept a matte, slightly rough surface.

vs Fused Deposition Modeling (FDM)

Choose SLS over FDM when you need more uniform mechanical properties, finer features, and freedom from support structures. SLS is better for complex enclosed geometries, nested parts, and batches of small components where FDM’s support removal and anisotropy become limiting.

vs Stereolithography (SLA)

Choose SLS over SLA when you need tougher, more impact-resistant parts that behave like nylon rather than brittle resin. SLS is better for snap fits, living hinges, and functional assemblies that will see repeated loading, even if you sacrifice some surface finish and fine detail.

vs Multi Jet Fusion (MJF)

Choose SLS over MJF when you prioritize broader material options (e.g., specialty nylons, elastomers) or are working with a shop that has SLS dialed in for your application. For many nylon parts, SLS and MJF are functionally similar; SLS can be a good choice when you value proven, widely available capacity and don’t need MJF’s slightly crisper detailing.

vs Digital Light Processing (DLP)

Choose SLS over DLP when you want mechanically robust nylon-like parts instead of very high-detail, brittle photopolymers. SLS is better for larger functional components, fixtures, and enclosures that must survive handling, impact, and temperature swings.

vs PolyJet

Choose SLS over PolyJet when durability, environmental resistance, and long-term stability matter more than ultra-smooth surfaces or multi-material aesthetics. SLS parts hold up better for real-world use, fixtures, and load-bearing prototypes, while PolyJet shines for visual models and soft-over-hard cosmetic concepts.

Design Considerations

  • Keep wall thickness between about 1.0–4.0 mm for most features to balance strength, warpage risk, and print cost
  • Add powder escape holes and internal drain paths for hollow or lattice parts so the shop can depowder effectively
  • Design in realistic clearances (typically 0.15–0.25 mm per side) for mating features and moving joints to account for tolerance and powder adhesion
  • Avoid very large, flat, solid panels; add ribs, cutouts, or slight curvature to reduce warping and improve dimensional stability
  • Orient and size embossed or debossed text and logos with at least 0.5 mm height/depth and stroke width for legibility after blasting
  • Group parts into logical sets and indicate critical-to-function dimensions on the drawing or model so the shop can tune orientation and inspection accordingly