Designing for MJF Powder Removal
MJF parts are built in a bed of powder. After printing, trapped powder must be removed from internal cavities, channels, and hollow sections. If powder can’t escape, it stays inside your part.
1. The Golden Rule
Every enclosed space needs an escape hole for powder removal. If powder goes in during printing, there must be a way for it to come out.
2. Escape Hole Guidelines
Minimum diameter: 3.5mm (smaller holes clog with compressed powder)
Recommended diameter: 5mm+ for reliable cleaning
Multiple holes: Add at least 2 escape holes per cavity so compressed air can flow through (one in, one out)
Placement: Put holes at the lowest point of the cavity (gravity helps) and at opposite ends
3. Channel and Tube Design
Minimum internal diameter: 4mm for straight channels, 6mm+ for channels with bends
Avoid 90-degree bends — Powder gets trapped in sharp corners. Use smooth curves with minimum 5mm radius.
Straight channels are best — The longer and more complex the channel, the harder powder removal becomes.
Maximum recommended channel length without an intermediate access hole: 50mm
4. Hollow Parts
Hollowing parts saves material and cost, but:
Wall thickness must be at least 1.5–2.0mm for structural integrity
Add escape holes (see above)
Consider adding internal ribs for rigidity if walls are thin
Indicate on your order that the part is hollow so our team handles it carefully during depowdering
5. What Makelab Does
We use compressed air and manual tools to remove trapped powder. For complex internal geometries, we may use bead blasting or ultrasonic cleaning. If powder cannot be fully removed due to geometry, we’ll notify you before completing the order.
6. Design Checklist
Every cavity has at least 2 escape holes (minimum 3.5mm each)
No dead-end channels
No sharp internal corners in channels
Wall thickness is at least 1.5mm
Complex internal geometry is flagged in order notes
Need help optimizing your MJF design? Send us your file for a free review.