SLS — Selective Laser Sintering
A CO₂ laser sinters nylon powder layer by layer — no support structures needed, unlocking geometry impossible with any other process.
SLS
Selective Laser Sintering
From a bed of nylon powder to a finished part
- Thin layer of nylon powder spread evenly across the build bed.
- CO₂ laser sinters powder at 170–200 °C in the part cross-section.
- Unsintered powder acts as self-support — no support structures needed.
- Platform drops, fresh powder spreads — process repeats.
- Parts dug from powder cake, bead-blasted clean.
What SLS is great at — and where it falls short
- No support structures — total design freedom
- Strong, functional nylon parts
- Good isotropy (~85% in Z vs XY)
- Chemical and water resistant
- Suitable for end-use production
- Watertight at walls ≥4 mm
- Grainy surface finish as-printed (Ra 3.2–7.6 µm)
- Parts come out grey — dyeable but not multi-colour
- Limited material range vs FDM
- 10–15% Z-direction strength reduction
- Higher cost than FDM for one-off parts
- Longer lead time than FDM
When to choose SLS
- Complex geometry with undercuts or internal channels.
- Functional Nylon parts intended for end-use.
- Batch of 5–50 parts where MJF would be overkill.
SLS materials we stock
Nylon PA12
A production-grade engineering thermoplastic valued for its excellent balance of strength, toughness, chemical resistance, and dimensional stability. Parts are built without support structures, enabling complex internal geometry and undercuts. Watertight at wall thicknesses of 4 mm or more. Widely used across automotive, aerospace, medical, and industrial applications.
Glass-Filled PA12 (PA12GB)
PA12 reinforced with 40% glass beads, delivering nearly double the stiffness of standard PA12 at 3,200 MPa tensile modulus. Offers superior wear resistance, enhanced thermal stability, and reduced warping — making it ideal for load-bearing structural parts, fixtures held under sustained load, and components operating in higher-temperature environments.
The numbers that matter
What tolerance means in practice: ±0.3 mm means a 10 mm hole prints between 9.7 mm and 10.3 mm. Good enough for most enclosures, brackets, captured assemblies and ducting. For tighter mating fits (bearings, threads) move to MJF (±0.2 mm) or SLA (±0.15 mm), or design with clearance and post-machine.
Rules to design freely
Forget Supports
SLS doesn't need supports — design with complete freedom.
Why: surrounding powder fully supports the part during printing.
Wall Thickness
Min wall 0.7 mm functional, 1 mm structural. For watertight: ≥4 mm.
Why: nylon powder needs enough mass to sinter cleanly between particles.
Clearance for Captured Assemblies
Allow 0.4 mm radial clearance for moving parts printed inside others.
Why: heat from the laser can fuse adjacent surfaces if clearance is too small.
Hole Sizing
Min hole diameter 1.5 mm. Smaller holes may sinter shut.
Why: residual heat in tight cavities can cause closed-up powder.
Powder Removal Channels
Hollow parts need ≥5 mm escape holes at lowest points to remove unsintered powder.
Why: trapped loose powder rattles or affects part weight and balance.
How SLS stacks up
| Property | FDM | SLA | SLS | MJF | SLM |
|---|---|---|---|---|---|
| Cost | $ | $$ | $$$ | $$$ | $$$$$ |
| Surface Finish | Visible layers | Near-smooth | Slightly grainy | Slightly grainy | Rough as-printed |
| Detail | Moderate | Excellent | High | High | High |
| Tolerance | ±0.5 mm | ±0.15 mm | ±0.3 mm | ±0.2 mm | ±0.2 mm |
| Strength | Anisotropic | Near-isotropic | ~85% iso | ~95% iso | Near-isotropic |
| Speed | Fast | Medium | Medium | Fast | Slow |
| Material Range | Wide | Resins | PA12, PA12GB | PA12, PA12GB, TPU | Al, SS, Ti, tool steel |
| Support-free | No | No | Yes | Yes | No |
| Best for | Prototypes | Visual & detail | Complex geometry | Production batches | Metal end-use |
Key Applications
Complex Functional Parts
Geometries that can't be machined or cast.
No-support freedom enables the impossible.
Ducting & Manifolds
Air, fluid, and exhaust routing with internal channels.
Internal geometry no other process can build.
Interlocking Assemblies
Single-print captured chains, hinges, articulated parts.
Surrounding powder lets parts move post-print.
Medical Device Housings
Surgical tool covers, prosthetic shells.
PA12 is biocompatible, sterilisable, robust.
Low-Volume Production
5–50 part batches without mould tooling.
Multiple parts nest in the same powder cake.
Snap-fit Enclosures
Robotics housings, electronics covers.
Strong nylon flexes without breaking on first close.
SLS, answered
Correct — the unsintered powder around the part fully supports it during printing. This is what enables complex geometry like internal channels, undercuts, and even moving captured assemblies in a single print.
The PA12 nylon powder is naturally white/grey. Parts can be dyed any colour after printing — black is standard, custom colours on request.
SLS PA12 reaches 80–85% of the strength of injection-moulded PA12 in the XY plane. The Z-direction is slightly weaker due to layer fusion, but still capable of end-use loads.
Yes — at wall thickness ≥4 mm, SLS parts are inherently watertight without sealing. Below 4 mm, a sealing coat is recommended.
Both use nylon powder. MJF uses inkjet agents for tighter tolerances (±0.2 mm vs ±0.3 mm) and better surface consistency, ideal for production batches. SLS has wider material options (including PA11 and TPU on request).
PA12 has good UV resistance compared to most resins and is suitable for many outdoor applications. For sustained sun exposure, dyeing black or applying a UV-resistant coating extends service life.