Powder bed fusion
What is SLS and how does it work?
A technology that fuses nylon powder layer by layer with a laser, producing durable functional parts without supports.
Selective Laser Sintering
In SLS, a thin layer of polymer powder (usually PA12 or PA11) is heated to just below its melting point, and a CO₂ laser scans the part's cross-section to melt and fuse the powder. Since the unfused powder supports the part from all sides, no separate support structures are needed, which allows nested, moving and complex geometries to be printed as one piece. After printing, parts are cooled, separated from the powder and bead blasted.
| Typical tolerance | ±0.3% (lower limit ±0.3 mm) |
|---|---|
| Layer thickness | 100 – 120 µm |
| Minimum wall thickness | 0.7 – 1 mm |
| Surface | Slightly rough, matte (bead-blasted texture) |
| Supports | Not required |
Process
SLS step by step
- 01
The powder bed is heated.
- 02
A roller or blade spreads a thin powder layer (typically 100 – 120 µm).
- 03
The laser scans the cross-section to fuse the powder.
- 04
The platform lowers one layer and the process repeats.
- 05
Cooled parts are removed from the powder and bead blasted; part of the powder is reused.
Advantages
- No supports: complex and nested geometries
- Durable, functional nylon parts
- Efficient series production by filling the build volume in 3D
- Nearly isotropic properties
Limitations
- Matte, slightly rough surface
- Shrinkage and warping in thick sections
- Limited colors (usually white/grey; dyed afterwards)
Best suited for
- Functional prototypes and end-use parts
- Hinges and snap-fit parts
- Air ducts
- Small series production
Design
SLS design guidelines
- Minimum wall thickness0.7 – 1 mm
- Smallest detail0.5 mm
- Minimum hole diameterØ 1.5 mm
- Overhang angleUnlimited (no supports needed)
- Clearance for moving parts0.5 mm (moving parts)
- Text and logosEmbossed ≥ 1 mm
- Escape holeAt least two Ø 5 mm powder escape holes in hollow parts
Surface and assembly
Post-processing
- Bead blasting
- Dyeing (black dip)
- Vapor smoothing
- Impregnation (watertightness)
Materials
Materials printed with SLS
PA12 (Nylon 12)
Polyamide 12 powder (SLS / MJF)
PA11 (Nylon 11)
Bio-based polyamide 11 powder
PA12 GB (glass beads)
Glass bead filled PA12
PA12 CF
Carbon fiber reinforced PA12 (SLS)
PA12 full color (MJF)
Full-color PA12 (HP Multi Jet Fusion color systems)
TPU / TPE (SLS / MJF)
Thermoplastic polyurethane and elastomer powders
PP (MJF / SAF)
Polypropylene powder
Good to know
Frequently asked questions about SLS
What is SLS?
In SLS, a thin layer of polymer powder (usually PA12 or PA11) is heated to just below its melting point, and a CO₂ laser scans the part's cross-section to melt and fuse the powder. Since the unfused powder supports the part from all sides, no separate support structures are needed, which allows nested, moving and complex geometries to be printed as one piece. After printing, parts are cooled, separated from the powder and bead blasted.
How does SLS work?
The powder bed is heated. A roller or blade spreads a thin powder layer (typically 100 – 120 µm). The laser scans the cross-section to fuse the powder. The platform lowers one layer and the process repeats. Cooled parts are removed from the powder and bead blasted; part of the powder is reused.
What applications is SLS suitable for?
SLS is especially suitable for functional prototypes and end-use parts, hinges and snap-fit parts, air ducts, small series production.
How accurate are SLS parts?
Typical tolerance is ±0.3% (lower limit ±0.3 mm). The exact value depends on the machine, material and part geometry.
Other technologies
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