3D printing processes
What is SLS 3D printing, and why is it used for functional parts?
SLS (selective laser sintering) 3D printing uses a laser to fuse PA12 nylon powder layer by layer. Loose powder supports the part, so nested, interlocking and internal-channel geometry needs no support structures. It suits tough functional parts and batches. On our service, SLS builds up to 165 × 165 × 300 mm at ±0.3% (minimum ±0.3 mm), from 2 calendar days.
Reviewed by HenleyPrint3D engineers2 min readUpdated
Key takeaways
- Material is PA12 nylon; tolerance ±0.3% with a minimum of ±0.3 mm.
- Build volume 165 × 165 × 300 mm; lead time from 2 calendar days.
- No supports, so internal channels and moving assemblies are possible.
- Hollow parts need escape holes of 4 to 5 mm or more for powder.
Suits
Housings, clips, snap fits, ducting and batches of small functional parts.
Worth knowing
Not for large parts or a smooth, glossy surface. Larger parts go to FDM, and the as-printed finish is matte.
SLS key figures
| Property | SLS on our service |
|---|---|
| Material | PA12 nylon |
| Build volume | 165 × 165 × 300 mm |
| Tolerance | ±0.3% (min ±0.3 mm) |
| Layer height | From 50 microns |
| Minimum wall | 0.7 to 1.0 mm |
| Powder escape holes | 4 to 5 mm or more |
| Lead time | From 2 calendar days |
SLS strengths and limits
| Good for | Watch out for |
|---|---|
| Housings, clips, snap fits, ducting | Matte, slightly grainy surface |
| Batches: parts nest in one build | Hollow parts need two escape holes |
| Interlocking and printed-in-place assemblies | One material only; larger parts go to FDM |
SLS or another process?
| If you need | Choose |
|---|---|
| Support-free internal channels | SLS |
| Snap fits and living hinges | SLS |
| A part larger than 300 mm | FDM |
| The finest surface | SLA |
Designing for SLS
Because loose powder supports the part, you can nest parts in three dimensions, print interlocking assemblies and add internal channels. The rules above cover escape holes and clearances. For material data and finishing options, see our PA12 nylon SLS guide, the SLS materials page and the SLS 3D printing service page.
For tolerance figures and fits, see 3D printing tolerances by process.
Frequently asked questions
What material does SLS use?
Most SLS work is done in PA12 nylon powder, which is strong, tough and slightly flexible. Other powders such as PA11, glass-filled nylon and TPU exist, but availability depends on the machine.
Does SLS need support structures?
No. The surrounding unsintered powder supports the part during the build, which allows complex geometry. Hollow parts need escape holes so the powder can be removed.
How accurate is SLS 3D printing?
On our service, typically ±0.3% with a minimum of about ±0.3 mm. Part size, geometry and cooling affect results, and critical features can be machined afterwards.
Is SLS cheaper than FDM?
For single large parts, FDM is usually cheaper. For batches or complex small parts, SLS can be more economical because many parts share one build and need no supports.
Are SLS parts waterproof?
Printed PA12 is slightly porous. For fluid or pressure applications, parts are typically sealed or coated, and testing should confirm suitability.
Get started
Talk to an engineer about your part.
Send us your CAD or describe the problem. We recommend the process, material and finish, and quote with the lead time up front.
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