SLS vs SLA vs MJF
Comparing powder sintering, resin curing and multi-jet fusion for plastic parts
Three powder- or resin-based plastic processes dominate functional prototyping and low-volume production: SLS (laser sintering of nylon powder), MJF (multi-jet fusion, also nylon powder with an ink-based thermal process) and SLA (laser-cured liquid resin). SLS and MJF produce durable, isotropic-ish nylon parts without supports; SLA gives the finest detail and surface at the cost of brittleness and support cleanup.
1. SLS (Selective Laser Sintering)
SLS fuses nylon (PA12) powder with a CO2 laser, layer by layer, inside a heated chamber. Un-sintered powder supports overhangs and internal channels, so no supports are needed and complex lattices print freely. Layer height 0.1–0.12 mm, tolerance ±0.3% (±0.3 mm), UTS ≈48 MPa with good fatigue.
SLS parts have a matte, slightly porous surface (Ra ~8–12 µm) and are strong enough for functional brackets, enclosures and snap fits. Dyeing and media blasting improve cosmetics; sealing reduces fluid permeability.
2. MJF (Multi Jet Fusion)
MJF deposits fusing and detailing agents on PA12 powder, then passes an infrared lamp to fuse selected regions — faster than laser sintering and with slightly finer detail (0.1 mm layers) and a more uniform surface. Mechanical properties are comparable to SLS; MJF edges are often crisper.
MJF is usually a few percent cheaper per part than SLS at identical geometry and quantity, with marginally better surface finish (Ra ~8 µm). Both are true production processes for end-use nylon parts, not just prototypes.
3. SLA (Stereolithography / resin)
SLA cures liquid photopolymer with a laser (or DLP projector): layers down to 0.025–0.05 mm, tolerance ±0.2% (±0.2 mm), and surface finish Ra 1–3 µm — the best of any polymer printing. Standard resin (UTS ≈44–65 MPa) is rigid but brittle-ish; engineering resins add toughness, heat resistance or flexibility.
The trade-offs: SLA needs support structures that leave marks, parts are photo-degrading and weaker in thin sections, and build size is limited (~300 × 335 × 200 mm typical). Use SLA for visual models, flow testing, molds (for low-volume casting) and fine features; not for high-impact or high-temperature duty.
4. Choosing between them
Durable end-use nylon with complex geometry → SLS or MJF (MJF for finer detail at similar cost). Fine detail, smooth surfaces, optical clarity options → SLA. High temperature or chemical duty → consider PA12-GF, PA11, or switch to metal DMLS. FDM remains the budget option when finish and accuracy are secondary.
All three quote on the platform with material, finish and quantity multipliers; upload the same model to all three to compare price and lead time directly.
Quick reference
| Metric | SLS | MJF | SLA |
|---|---|---|---|
| Material | PA12 / PA11 / GF | PA12 / PA11 / TPU | Standard & engineering resins |
| Layer height | 0.1–0.12 mm | 0.1 mm | 0.025–0.05 mm |
| Tolerance | ±0.3% (±0.3 mm) | ±0.3% (±0.3 mm) | ±0.2% (±0.2 mm) |
| Surface | Matte, ~8–12 µm | Smooth matte, ~8 µm | Ra 1–3 µm (smoothest) |
| Supports | None needed | None needed | Required |
| Strength | ≈48 MPa UTS, tough | ≈48 MPa UTS, tough | 44–65 MPa, brittle-ish |
| Best for | Functional nylon parts | Fine-feature nylon parts | Visual, detail, molds |
Sources & references
- ISO/ASTM 52911 (powder bed fusion)
- ASTM F2921 (additive designations)
- Xometry Learning Center — SLS vs SLA vs MJF (public engineering reference)