SLS 3D printing
- Layer thickness
- 0.11 mm
- Maximum volume
- 330 × 330 × 565 mm
- XY tolerance (PA12)
- ±0.3 mm or ±0.5%
- Usual lead time
- 3–5 working days
Process
How SLS printing works
- 01
Packing the parts
The parts are arranged in software across the whole chamber volume, next to and above each other, with a few millimetres of powder between them. The fuller the chamber, the lower the cost per part.
- 02
Heating
The chamber and the powder are brought close to the melting point of the polymer. The laser only has to add the difference, so the layers bond well without warping.
- 03
Sintering
The laser first traces the outline of each cross-section, then fills it with parallel hatch lines. The hatch angle rotates from one layer to the next, so the part has no weak direction.
- 04
New layer
The platform drops by 0.11 mm and a blade spreads a new layer of powder. The cycle repeats a few thousand times until the last layer.
- 05
Cooling
At the end, the parts sit in a block of warm powder that cools down slowly. If they were taken out too early, they would warp.
- 06
Depowdering and blasting
We take the parts out of the powder block, recover the unsintered powder for the next build, then blast the parts automatically to an even matte surface.
Comparison
SLS compared with FDM, SLA and MJF
| Criterion | SLS | FDM | SLA | MJF |
|---|---|---|---|---|
| Supports | no | yes | yes | no |
| Typical materials | PA12, PA11, TPU, PP | PLA, PETG, ABS, PA | photopolymer resins | PA12, PA11, TPU, PP |
| Strength in Z | close to XY | noticeably weaker | good, but the material is brittle | close to XY |
| Surface | matte, slightly grainy | visible layers | smooth, fine | matte, slightly grainy |
| Raw colour | grey or white | any filament | depends on the resin | dark grey |
| Good for | functional parts, low volumes | simple, cheap brackets | fine detail, appearance | low volumes, black parts |
SLS and MJF produce parts from the same material families; the differences are colour, surface and availability. The full comparison is in the guide. Read the guide. For nylon parts, the detailed comparison with MJF is in the guide SLS or MJF.
Precision and surface
Precision and surface of the parts
The surface of an SLS part is matte and slightly grainy. After automated blasting, Formlabs measured a roughness of about Ra 8–16 µm on PA12, depending on the face.
For PA12 the usual tolerance is ±0.3 mm or ±0.5% in X and Y, whichever is larger. In Z, the build axis, deviations are somewhat larger. You mark critical dimensions in your request, and tight fits are made by reaming or with bushings.
Minimum values for walls, holes and clearances are in the SLS design guide.
Production and lead times
Why does cooling take so long?
When printing finishes, the parts sit in hot powder and have to cool gradually. If they are taken out too early, they can warp. Formlabs gives a cooling time of up to half the print time. That is why, even if we start a build in the evening, the parts are not necessarily ready the next morning.
What is the maximum part size?
On the Fuse X1 the build volume is 330 × 330 × 565 mm, and on the Fuse 1+ 30W it is 165 × 165 × 300 mm. The usable part size is slightly smaller than the build volume and varies from material to material. Also, not every material runs on both printers. Larger parts are split into segments that are bonded or fastened together mechanically.
What post-processing is included?
Depowdering in the Fuse Sift and automatic blasting in the Fuse Blast are included. Blasting removes the remaining powder and evens out the surface. Colouring, protective lacquer, extra polishing and fitting threaded inserts are discussed separately and appear in the quote if you ask for them.
Can you produce repeat batches with the same results?
Yes, as long as we use the same files, material and orientation. Formlabs reports stable X and Y dimensions between builds and between positions in the chamber. If you have critical dimensions, tell us which they are with your first order, so we keep the same orientation for them in later batches.
Send your file and we'll tell you what the part costs
- Free quote
- No minimum quantity
- NDA on request