Technologies
MJF vs SLS: which to choose for nylon parts
MJF vs SLS for nylon parts: how each works, build volumes, materials, finish, isotropy and lead times, plus when each process is the better choice.
MJF and SLS both fuse nylon powder without supports, but each one shines in a different situation. At EptaPrint, SLS is the choice for prototypes and small batches in PA12 and TPU, delivered on the Express, Rapid or Economy tier; MJF pays off for larger runs, thanks to a 380 × 284 × 380 mm usable build volume that is filled with many parts per build and a wider range of materials.
How SLS and MJF work
Both build the part layer by layer in a bed of polymer powder; what differs is how the powder gets fused.
- SLS (Selective Laser Sintering): the nylon powder is held just below its melting point. On each layer, about 100 µm thick, a roller spreads the powder and a laser, steered by the scanner mirrors, sinters the cross-sections of the parts.
- MJF (Multi Jet Fusion): on each 80 µm layer an inkjet head deposits a fusing agent over the cross-section and a detailing agent along its edges, then an infrared lamp fuses only the treated area.
In both processes the unfused powder supports the parts. There are no supports to remove, internal channels and lattices are possible, and the build volume can be packed with many parts in the same build, which brings the unit cost down.
SLS vs MJF at a glance
Accuracy and build volume are in the same range: the differences that drive the decision are materials, quantity and lead time.
| Feature | SLS | MJF |
|---|---|---|
| How the powder is fused | laser | inkjet agents and infrared lamp |
| Max build volume | 330 × 330 × 565 mm | 380 × 284 × 380 mm |
| Layer thickness | 0.1 mm | 0.08 mm |
| Dimensional accuracy | ±0.3% (minimum ±0.3 mm) | ±0.3 mm up to 100 mm, ±0.3% above |
| Minimum feature or wall | 0.5 mm feature | 1 mm wall |
| XY/Z isotropy | ~85–90% | near-isotropic (PA12: 48 MPa in XY and Z) |
| As-built surface | uniform, Ra 8–12 µm | matte, slightly grainy |
| Catalog materials | PA12, TPU | PA12, PA12 White, glass-bead-filled PA12, PA11, PP, TPU |
| Lead time | Express 48–72 hours, Rapid 5 days, Economy 7+ days | stated in the quote |
Values as published on our SLS 3D printing and MJF 3D printing pages; tolerances are typical as-built values.
Surface finish and isotropy
Both processes produce parts far more isotropic than FDM, and MJF comes closest to identical properties in every direction.
SLS. Mechanical isotropy is around 85–90%, compared with 70–80% for FDM. The as-built surface is uniform (Ra 8–12 µm) but slightly porous: for fluid-tight or gas-tight parts we apply a sealing treatment such as vapor smoothing, resin infiltration or painting.
MJF. Parts are dense with low porosity, and PA12 reaches a tensile strength of 48 MPa both in the build plane and along Z. As-built, PA12 is gray with a matte, slightly grainy surface; on request we can assess black dyeing or painting, and PA12 White is the base for light colors.
Available materials
SLS covers the two most requested materials, while MJF offers more choice.
- SLS: Nylon PA12, the 3D printing counterpart of injection-molded nylon for functional parts, and TPU powder for flexible parts such as gaskets.
- MJF: PA12, PA12 White, PA12 filled with glass beads, PA11, polypropylene (PP) and TPU.
For PA12 the starting point is the same: our catalog lists a tensile strength of 48 MPa in both processes. How the MJF materials differ (the ductility of PA11, the chemical resistance of PP, the stiffness of glass-filled PA12) is covered in our guide to MJF materials: PA12, PA11, PP and TPU; HDT, tensile strength and elongation for each one are in the materials catalog.
When SLS wins and when MJF wins
SLS wins when you need a few parts on a firm schedule; MJF wins as quantity or material requirements grow.
Choose SLS for:
- functional prototypes and small batches in PA12 or TPU;
- parts up to 330 × 330 × 565 mm, including tall ones;
- rush jobs: on the Express tier the part is ready in 48–72 hours;
- fast design iterations, when the design changes from one batch to the next.
Choose MJF for:
- larger runs that fill the build volume with many parts per build;
- parts up to 380 mm long, beyond the 330 mm side of the SLS build volume;
- materials SLS does not offer: PA11 for snap-fits and living hinges, PP for ducts and fluid-contact parts, glass-filled PA12 for stiffness and low shrinkage;
- dense parts where tightness matters without a sealing treatment.
When a part is headed for production in PA12, a sensible path is to validate the design in SLS and move to MJF for the run, keeping the same base polymer.
How to choose in practice
- Size: SLS builds up to 330 × 330 × 565 mm, MJF up to 380 × 284 × 380 mm: the volumes are comparable, so the part's envelope decides.
- Material: PA11, PP, PA12 White or glass-filled PA12 are MJF only; PA12 and TPU are available in both.
- Quantity: prototypes and small batches in SLS; runs that fill the build volume in MJF.
- Timing: if you need a firm date up front, SLS has delivery tiers; for MJF the lead time is in the quote.
- Tightness: MJF PA12 is dense; SLS needs sealing for fluid-tight applications.
Where to start
Upload your CAD through the quote form with quantity, material and finish: within 24 business hours you get a quote with the most cost-effective process for your part and, for MJF, the lead time. If the part was designed for injection molding or CNC machining, our DfAM consulting adapts it to powder bed processes before production.