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Design for CNC & Laser

Subtractive manufacturing - CNC routing, milling, laser cutting, and sheet-metal bending. Design so the machine can actually cut it.

1 Experience
2 Reflect
3 Theorize
4 Apply

CNC Milling & Routing

A CNC mill spins a round cutter and carves material away. Because the cutter is round, every internal corner on the part will also be round - you literally cannot cut a perfectly sharp inside corner.

CNC Design Rules
  • Internal fillets required: Every inside corner gets a radius ≥ the end mill radius (typically 1.5-3 mm).
  • Pocket depth-to-width: Keep pockets shallower than 4x their width so the cutter stays stiff.
  • Minimum wall: 1 mm for aluminum, 1.5 mm for plastic - thinner walls chatter.
  • Drill full through: Blind holes (bottomed out) cost extra - design through-holes when possible.
Export for CNC: Use STEP format. It preserves exact curves, tolerances, and the feature tree - everything the shop's CAM programmer needs.

Laser Cutting

A laser cutter burns a thin slit through flat sheet material. It's fast, cheap, and perfect for robot plates - but only works for 2D profiles.

Laser Design Rules
  • Kerf: The laser beam has width (0.1-0.3 mm). Features smaller than kerf simply disappear.
  • Min feature size: Don't design anything smaller than the material thickness (e.g. 3 mm acrylic = 3 mm min feature).
  • Tabs & slots: Make slots 0.1 mm wider than the mating tab so parts press-fit together.
  • Engrave vs cut: Vectors on one layer are cuts, another layer is engraves. Plan them in advance.
Export for laser: DXF format. Check units before uploading - a drawing in inches on a mm-configured machine will cut tiny parts from a huge sheet.

Sheet Metal - Bending & Forming

Sheet metal parts start as a flat pattern, get cut (usually by laser), then folded on a press brake. Perfect for chassis plates, electronics enclosures, and guards.

Sheet Metal Rules
  • Bend radius ≥ material thickness: Bending tighter cracks the metal. Typical 1.5-2x thickness.
  • Reliefs on bend corners: Cut a small slot where bends meet so metal doesn't tear.
  • Hole distance from bend: Holes must be at least 2.5x material thickness from a bend, or they'll deform.
  • K-factor: Controls how the flat pattern unfolds. Start at 0.42 for mild steel, 0.38 for aluminum.
Sheet Metal Workflow in CAD
1
Switch to Sheet Metal Workspace

CAD tools have a dedicated mode that tracks bends and flat patterns for you.

2
Start with a Flange

Draw one face, then use Flange or Tab tools to add bent walls.

3
Flatten the Pattern

Unfold the part back into a flat sheet to generate the cut profile.

4
Export DXF for the Cutter

Export the flat pattern as DXF, label bends clearly for the operator.

Pick the Right Process

CNC Mill

Complex 3D parts in aluminum or steel. Expensive per hour but incredibly accurate.

CNC Router

Big flat wood or plastic parts. Cheaper than a mill but less precise.

Laser Cutter

2D profiles in thin sheet - acrylic, plywood, cardboard, thin metal.

Sheet Metal

Bent steel or aluminum chassis and enclosures. Combined with laser or stamping.

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

Design a laser-cut chassis plate with bent tabs, ready for fabrication.

  • Sketch the outer chassis outline in 2D
  • Add bolt hole patterns at least 5 mm from the edges
  • Convert two edges into folded-up flanges (sheet metal)
  • Flatten the pattern and export as DXF
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