Parametric design

In a parametric model, dimensions are linked by rules: outside = part + 2 × (clearance + wall). Change the part, and everything that depends on it updates. Name the numbers that drive the design, and work the rest out from them.

1. A bigger part
2. Try: change the part › A wider part
3. Try: change the part › Less clearance
4. Worked example: write the rules › Driving and driven
5. Worked example: write the rules › Find the mistake
6. Practise: rules › Which drives?
7. Practise: rules › The lid
8. The biggest part

A laser beam burns away a thin strip as it cuts: the kerf. So a cut slot comes out wider than drawn (by the kerf) and a cut-out part a little smaller. Draw slots narrower than the board for a snug press fit.

1. A 3 mm slot
2. Try: make it snug
3. Worked example: allow for the kerf › Back from the board
4. Worked example: allow for the kerf › Find the mistake
5. Vary: a finer beam
6. Practise: kerf › A square
7. Practise: kerf › Finger joints
8. Thicker board