Designing with CAD and modelling
Design & Technology · Key Stage 3 · The School
What CAD is actually for
COMPUTER AIDED DESIGN is not neat drawing. Its value is that the model is DIMENSIONED and PARAMETRIC: change one dimension and everything referencing it updates. You can test fit before cutting anything, produce accurate views automatically, and hand a file to a machine. A sketch is still faster for the first twenty ideas — CAD earns its place once an idea is worth being precise about.
CAD to CAM
COMPUTER AIDED MANUFACTURE takes that file and drives a machine: a laser cutter, a 3D printer, a CNC router. The chain is CAD file → toolpath → machine. Because the file is exact, the parts are repeatable, which is what makes batch production possible. It also means an error in the file is faithfully reproduced in every single part.
Why you still make one
A screen cannot tell you whether a handle is comfortable, whether a lid is stiff to open, or whether something looks heavy. Card, foam and tape answer those in minutes. The sensible order is: sketch to think, model to test with a person, CAD to make it precise, CAM to make it real. Skipping the physical model is the commonest reason a well-drawn product is unpleasant to use.
Draw a box in CAD, 200 mm wide. Change that dimension to 250 mm: the front view, the plan, the side view, the cutting list and the volume all update at once. Do the same to a hand drawing and you redraw three views and recalculate. Then send the CAD file to a laser cutter and it cuts. Then still build a card model — because CAD will never tell you the handle is uncomfortable.