When to pick MJF over SLS
MJF deposits a fusing agent on a powder bed and then floods the layer with IR. The result: near-isotropic mechanical properties (within ~5 % between Z and XY), > 99 % density, and Ra ~5 µm — better than SLS on every axis.
Pick MJF for functional plastic parts at production volume: housings, ducts, end-effectors, jigs, fixtures, and short-run consumer goods.
Defects and post-processing
Powder reuse is the dominant quality variable: virgin powder ratio below 80 % causes brittleness. Parts emerge with a uniform gray surface that takes dye well.
Bead-blast for finish; dye black or other colors as a single-step bulk coloring.
Suggested parameters
HP MJF 5200 standard process.
- Layer thickness: 80 µm
- Build rate: ~3500 cm³/hr (volumetric)
- Build chamber: 380 × 284 × 380 mm
- Cool-down: 24–48 h before depowder
- Powder refresh: ≥ 20 % virgin per build
Frequently asked questions
Is MJF PA12 watertight?
Out of the bed, yes for walls > 1.5 mm at low pressure. For pressurized fluid applications, seal-coat or post-infiltrate.
What's the realistic minimum feature size?
0.5 mm walls and 0.5 mm holes print reliably. Below that, features survive but are powder-clogged.
Sources
- HP MJF 5200 PA12 datasheet
- ASTM F3091 — AM Polymer Parts Standard Guide