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17 Manufacture

Design for 3D Printing

FDM, resin, and SLS - design your parts so they print reliably the first time, not the fifth.

1 Experience
2 Reflect
3 Theorize
4 Apply

Additive Manufacturing Basics

3D printing builds a part layer by layer. Because each layer glues onto the last, parts are weaker between layers than along them. Good design works with that grain.

FDM (Fused Filament) - The Most Common
  • Overhangs: Anything hanging out past 45° needs support material. Design chamfers at 45° to stay self-supporting.
  • Walls: 1.2 mm minimum for decorative, 1.6-2.4 mm for anything structural.
  • Infill: 25-40% gyroid infill is the sweet spot for strength and print time.
  • Layer orientation: Put the load along the layers, never across them.
Resin (SLA / DLP)
  • Accuracy: Excellent surface finish, fine features down to 0.1 mm.
  • Supports: Almost every part needs them - plan orientation carefully.
  • Brittleness: Standard resin is rigid. Use "tough" or "flex" resins for functional parts.
SLS (Powder-based Nylon)
  • No supports needed: The unsintered powder holds everything up.
  • Complex geometry: Hinges and lattices can be printed in place.
  • Min feature: 0.8 mm walls are realistic; thinner parts warp.

DFM Rules for 3D Printing

3D Print Design Checklist
1
Pick the Orientation First

Load direction should run parallel to the layers. Rotate the part before drawing supports.

2
Keep Walls Thick Enough

1.2 mm absolute minimum. For screw bosses use at least 2.4 mm around the thread.

3
Avoid Sharp Overhangs

Turn overhangs above 45° into chamfers or add a bridge - don't rely on messy supports.

4
Add Clearances for Fits

Holes need +0.2 mm clearance for bolts; moving parts need 0.4-0.6 mm.

5
Export STL or 3MF

3MF keeps color, units, and multiple bodies together - prefer it when the slicer supports it.

Common fail: Tiny pegs printed vertical. Layers pull apart under any side load. Either print them flat, thicken them to >3 mm, or switch to a metal screw insert.
⚙

Challenge

Find the print orientation that maximizes strength while keeping support material under 20%.

⚠ Predict First

Which print orientation do you think will produce the strongest part?

Stage 2 Pause and Reflect
✓ Your reflections are saved automatically
Stage 4 Apply What You Learned

Take your robot's sensor bracket and prepare it for FDM printing.

  • Identify the primary load direction on the bracket
  • Pick a print orientation that puts layers parallel to the load
  • Redesign any overhang over 45° into a chamfer
  • Add +0.2 mm clearance to each bolt hole
  • Export as 3MF and check the slicer's support preview
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