Designing for 3D Printing (DFM)
Tolerances, orientation, wall thickness and overhangs — design models that actually print well.
Design for How It's Built
A model that looks great in CAD can be miserable to print. Designing for the process — not against it — saves supports, failures, and post-processing. The big levers are orientation, wall thickness, tolerances, and overhang angles.
Wall Thickness and Features
Keep walls a sensible multiple of your nozzle and line width:
- Minimum wall: at least 2× line width (e.g. 0.8 mm for a 0.4 mm nozzle) so it prints solid
- Avoid tiny pins and thin tabs — they're fragile and hard to print
- Embossed/engraved text should be at least ~0.6 mm wide and ~0.4 mm deep to survive
- Add fillets to corners to reduce stress concentrations and warping
Tolerances and Fit
Plastic shrinks slightly and the nozzle leaves a finite line, so designed dimensions aren't exact. For parts that fit together, build in clearance:
- Loose/sliding fit: ~0.4–0.5 mm gap
- Snug/press fit: ~0.2–0.3 mm gap
- Holes print slightly undersized — oversize them or plan to drill/ream
Print a small tolerance test for your specific printer once, and reuse those numbers.
Orientation Is a Design Decision
How a part sits on the bed affects strength, surface finish, supports, and accuracy. Layer lines are the weak axis, so orient parts so loads run along layers, not across them.
Put the most important faces up or vertical (they look best), avoid steep overhangs by rotating, and keep a large flat face on the bed for adhesion. Thinking about orientation in CAD — before you ever slice — is what separates parts that 'just work' from constant fiddling.