MJF
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Multi Jet
Fusion

HP's process jets fusing and detailing agents across entire powder layers simultaneously — achieving throughput and mechanical isotropy that SLS cannot match.

Production-grade polymer AM

Unlike SLS, MJF deposits fusing agent across the entire layer simultaneously using industrial inkjet printheads. A detailing agent is also jetted at boundaries for sharp edge definition. An infrared lamp then fuses the layer uniformly and rapidly.

MJF parts are typically more isotropic than SLS — Z-axis strength is ~85–90% of XY. This mechanical predictability makes it attractive for production-grade end-use parts.

Advantages

  • High throughput — full build volumes completed in hours
  • Excellent mechanical isotropy batch-to-batch
  • Good surface finish — better than standard SLS output
  • Full-colour MJF available (HP Jet Fusion 5200 series)
  • Scalable economics for medium-volume production runs

Limitations

  • Limited to PA12, PA11, TPU, and PP materials currently
  • Parts are initially gray/black from fusing agent color
  • High machine cost comparable to SLS
  • Powder waste management and recycling procedures required

MJF Specifications

Layer Height80µm standard
Tolerances±0.3mm
Build Volume380×284×380mm (HP 4200)
MaterialsPA12, PA11, TPU, PP
Support StructuresNot required ✓
Build SpeedUp to 4,115 cm³/hr
Surface FinishGood (slightly grainy)
Best ForProduction polymer parts
Fundamentals
MJF Basics

How HP's Multi Jet Fusion deposits fusing and detailing agents across entire powder layers to achieve production-grade throughput and mechanical consistency.

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Inkjet Printhead Array
MJF uses wide-format industrial inkjet printheads spanning the full build width, jetting fusing agent (and detailing agent at boundaries) across the entire powder layer in a single pass.
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Fusing & Detailing Agents
Fusing agent (dark, IR-absorbing) is jetted where the powder should fuse. Detailing agent (clear, IR-reflecting) is jetted at boundaries to prevent heat spread and achieve sharp edges. An infrared lamp then passes over the layer.
Throughput Advantage
MJF's full-layer-at-once approach delivers up to 4,115 cm³/hr — significantly higher than laser-based SLS. The time advantage scales with layer area: larger cross sections benefit proportionally more from MJF.
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Colour MJF
HP's 5200 series adds CMYK colour agents alongside the fusing agent — producing fully coloured parts without painting. Colour penetrates 0.2–0.5mm into the surface, enabling production of visually differentiated parts at no extra manufacturing step.
Part Colour & Dyeing
Standard MJF parts emerge dark grey-black due to the fusing agent's carbon-black pigment. Parts can be dyed in a range of colours post-build using fabric dyes in a hot water bath — the dye penetrates evenly into the porous surface.
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Powder Management
Like SLS, unsintered MJF powder is collected, sieved, and recycled. HP specifies a 20:80 (fresh:used) refresh ratio for standard PA12. The 5200 series integrates automated powder management for lights-out production.
Step 01
Prepare & Nest
Use HP SmartStream 3D Build Manager to nest parts and optimise build density.
Step 02
Print
Printhead jets agents; IR lamp fuses layer. Typical build: 8–24 hours for full chamber.
Step 03
Cool
Controlled cooling 4–8 hours in build unit. Transfer to processing station.
Step 04
Unpack
Automated or manual depowdering. Compressed air cleans cavities. Powder recycled.
Step 05
Post-process
Media blast for uniform surface. Dye, seal, or spray coat as required per application.
Deep Engineering
MJF Engineering

Why MJF outperforms SLS in isotropy: MJF's whole-layer IR fusing creates a more uniform thermal history across the layer than point-by-point laser scanning in SLS. Z-axis UTS in MJF PA12 typically reaches 48–52 MPa vs 42–46 MPa for SLS PA12. Batch-to-batch Cv (coefficient of variation) for MJF is typically <3% — critical for validated production parts.

<3%
Batch-to-batch
property Cv
MJF vs SLS Engineering Comparison
PropertyMJF PA12SLS PA12
XY Tensile Strength~48 MPa~46 MPa
Z Tensile Strength~48 MPa~40 MPa
Elongation at Break (XY)~20%~15%
Build Speed (full bed)Faster (+30–50%)Baseline
Surface Ra (as-built)~12 µm~18 µm
Powder Refresh Rate20% fresh30–50% fresh
Fusing Agent Chemistry & IR Absorption
  • Fusing agent absorption at 800–1100nm (near-IR) matches IR lamp emission peak
  • Detailing agent contains IR-reflective titanium dioxide — reflects IR at boundaries with high precision
  • Agent volume per layer is actively controlled — variation causes porosity or surface roughness
  • Printhead maintenance (purging, capping, nozzle health checks) is critical to agent uniformity
  • Agent jetting frequency reaches 100M drops/sec across full carriage width
Material Qualification & Validation
  • IQ/OQ/PQ (Installation, Operational, Performance Qualification) required for regulated industries
  • Witness coupons printed in every build — tensile bars tested per ISO 527-2 for traceability
  • Powder age tracking: each batch assigned MFI value — parts from powder outside spec rejected
  • CT scanning for complex geometries with internal features — verifies wall thickness and porosity
  • ISO 17296-3 covers AM general requirements; ASTM F3049 covers powder characterisation
DfAM for MJF
  • Minimum wall: 0.5mm — thinner walls may not fully fuse; 1.0mm recommended for structural features
  • Hollow parts: drainage holes ≥6mm required for powder evacuation
  • Lattice structures: gyroid and sheet lattices achievable at 0.8–1.0mm wall
  • Text and logos: minimum embossed/debossed depth 0.5mm, width 0.8mm for legible characters
  • Living hinges in PP (HP 3D HR PP): 1.0–2.0mm thickness, unlimited flex cycles at low strain
  • Avoid large horizontal cross sections at the same Z height — heat accumulation causes property variation
Production Scale Economics
  • Typical MJF cost breakeven: 1,000–10,000 parts/month vs injection mould
  • No tooling cost: eliminates ₹5–50L mould investment for low-volume production
  • HP Build Manager provides real-time cost estimates per part based on volume, orientation, and packing density
  • Warehouse-free manufacturing: print-on-demand eliminates inventory holding cost for spare parts
  • HP 5200 series supports 3-shift production: automated powder handling, multi-build-unit hot swap
Defects & Process Control
Undersaturation
Cause: Insufficient fusing agent
Fix: Check printhead nozzle health; recalibrate agent volume
Bleed
Cause: Fusing agent spread beyond boundary
Fix: Increase detailing agent volume; check build temperature
Warping
Cause: Thermal gradient in large flat parts near edges
Fix: Reorient at 45°; use support shells in SmartStream
Powder Sticking
Cause: Aged powder with low flowability
Fix: Enforce refresh rate; check Hausner ratio before build