MJF — Multi Jet Fusion
HP's Multi Jet Fusion delivers tighter tolerances and better surface consistency than SLS — the go-to for functional nylon parts in production quantities.
MJF
Multi Jet Fusion
From inkjet agents to production nylon parts
- Thin PA12 nylon powder layer spread across the build bed.
- Inkjet heads deposit fusing agent on part cross-section and detailing agent at boundaries.
- IR lamp passes over — inked powder fuses, loose powder stays.
- Repeats layer by layer until build completes.
- Powder cake moves to processing station — parts removed and bead-blasted.
What MJF is great at — and where it falls short
- Tighter tolerance than SLS (±0.2 mm vs ±0.3 mm)
- Nearly isotropic (~95%) — strong in every direction
- Better batch-to-batch consistency
- Fast production speed for batches
- Self-supporting — no support marks
- Excellent for 10–500 part batches
- Limited to PA12 / PA12GB (TPU on request)
- Grey as-printed (dyeable to black)
- More expensive than FDM for one-off prototypes
- Fine optical surfaces still better with SLA
- Less material variety than FDM
MJF materials we stock
PA12 Nylon
HP's high-reusability PA12 powder — a fine polyamide material with excellent elasticity, high impact resistance, and outstanding chemical resistance. Produces strong, detailed parts with uniform mechanical properties and consistent surface finish across batches. Nearly isotropic at ~95%, making it reliable for functional end-use components and production runs where repeatability matters.
PA12GB (Glass-Bead Filled)
PA12 infused with 40% glass beads for improved stiffness and structural integrity. Reduces warping on large flat parts and maintains dimensional accuracy under load. Higher stiffness and better thermal stability than standard PA12, at the cost of some flexibility. Ideal for flat structural components, mounting plates, and parts that must hold tight tolerances over time.
The numbers that matter
What tolerance means in practice: ±0.2 mm means a 10 mm hole prints between 9.8 mm and 10.2 mm — tight enough for press-fits and most production assemblies. For very tight bearing seats or sealing faces, design 0.1 mm under-size and post-machine, or use SLM with machined-critical features (±0.025 mm).
Rules to design for production
No Supports — Design Freely
Same as SLS — design with complete geometric freedom.
Why: surrounding powder fully supports each layer.
Wall Thickness
Min wall 0.5 mm functional. For watertight: ≥3 mm.
Why: thinner walls may not have enough mass for clean fusion.
Clearance for Assemblies
Allow 0.2–0.4 mm radial clearance between mating parts.
Why: even with MJF's tighter tolerance, parts can fuse if too close.
Nest for Cost Efficiency
Design multiple parts to nest in one build — cost per part drops at 10+ qty.
Why: MJF charges by build volume; tightly packed builds are lower cost per part.
Hole Sizing
Min hole diameter 1 mm. Larger is more reliable.
Why: detailing agent improves edges but very small holes still risk fusing.
Powder Escape Holes
Hollow parts need ≥4 mm escape holes at lowest points.
Why: trapped powder can't be removed and adds weight unpredictably.
How MJF stacks up
| Property | FDM | SLA | SLS | MJF | SLM |
|---|---|---|---|---|---|
| Cost | $ | $$ | $$$ | $$$ | $$$$$ |
| Surface Finish | Visible layers | Near-smooth | Slightly grainy | Slightly grainy | Rough as-printed |
| Detail | Moderate | Excellent | High | High | High |
| Tolerance | ±0.5 mm | ±0.15 mm | ±0.3 mm | ±0.2 mm | ±0.2 mm |
| Strength | Anisotropic | Near-isotropic | ~85% iso | ~95% iso | Near-isotropic |
| Speed | Fast | Medium | Medium | Fast | Slow |
| Material Range | Wide | Resins | PA12, PA12GB | PA12, PA12GB, TPU | Al, SS, Ti, tool steel |
| Support-free | No | No | Yes | Yes | No |
| Best for | Prototypes | Visual & detail | Complex geometry | Production batches | Metal end-use |
Key Applications
End-Use Production Housings
Customer-facing enclosures shipped at scale.
Tolerance and consistency match injection moulding.
Medical Device Components
Sterilisable tool covers, fixtures, brackets.
PA12 is biocompatible and dimensionally stable.
Consumer Product Enclosures
Phone cases, peripheral housings, smart-home covers.
Black-dyed finish reads as production-quality.
Automotive Brackets & Ducts
Under-hood mounts, ductwork, trim retainers.
Heat-resistant and stiff with PA12GB.
Complex Assemblies at Volume
Captured-pin mechanisms, hinges in production.
No-support build + repeatable tolerances.
Wearable Components
Watch bands, sensor housings, fitness device shells.
Light, strong, customer-facing finish.
MJF, answered
MJF uses inkjet agents for better dimensional consistency (±0.2 mm vs ±0.3 mm) and is faster for batches. SLS has a wider range of materials (PA11, TPU on request). For production Nylon parts, MJF usually wins.
Multiple parts nest together in a single build — the cost per part drops significantly at 10+ quantities. The HP system also has faster cycle times than laser-based SLS.
Standard parts are grey. Black dye is the standard post-process — uniform and penetrates fully. Other colours (red, blue, etc.) are available on request.
MJF PA12 is nearly isotropic at ~95% — meaning strength is almost equal in all directions, unlike FDM which is notably weaker in Z. Tensile strength reaches 48 MPa.
Yes at wall thickness ≥3 mm — slightly better than SLS at the same thickness due to tighter layer fusion. For thinner walls, ask for a sealing coat.
STL or STEP. We recommend STEP for production parts with tight tolerance requirements — it preserves CAD precision better than mesh formats.