Design guide
Overhangs & supports
FDM builds upward, layer on layer. Every surface needs something underneath it, either the previous layer, or a support structure that you'll later snap off.
The 45° rule (and why it's wrong)
The classic guidance is “45° is fine, anything steeper needs support.” That's a useful floor, but modern slicers and well-cooled materials can comfortably hold 50-60° without supports. Anything steeper than that, measured from vertical, starts to droop, sag, or peel at the layer boundary.
Angles measured from the build plate. 70°+ overhangs almost always need support.
Per-material limits
Cooler-running materials (PLA) hold steeper overhangs because each layer solidifies before the next one piles on. Enclosed materials (ABS, ASA, PA-CF) run hotter for layer adhesion and sag earlier.
| Material | Max overhang from vertical | Unsupported bridge (mm) |
|---|---|---|
| PLA | 60° | 20 |
| PETG | 50° | 12 |
| ABS | 45° | 8 |
| ASA | 45° | 8 |
| PA-CF | 45° | 6 |
| TPU | 40° | 4 |
Bridges are spans across empty air. Beyond the listed length, expect sag.
How to design supports out
- Chamfer instead of fillet on downward-facing edges. A 45° chamfer prints clean; a fillet's underside hangs unsupported.
- Split the part at a natural seam and glue or screw it together , often eliminates supports entirely and gives a better surface finish where it matters.
- Re-orient on the bed. Lying a bracket on its side often turns a 90° overhang into a manageable 30°. Tell us in checkout notes if you have a preferred orientation.
- Use teardrop or hexagonal holes for horizontal openings. Round horizontal holes need supports above the equator; teardrops don't.
Supports cost time, not much money
Our slicer adds tree supports automatically when needed. Supports add maybe 10-15% to print time and leave faint witness marks where they break off. They're not a disaster, but designing them out gives a better surface and a cheaper print.
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Last reviewed May 2026 · Rigid Prints engineering team