Manufacturing processes and scale
Design & Technology · Key Stage 3 · The School
Shaping
CASTING — pour molten material into a mould. MOULDING — injection moulding forces molten polymer into a die; vacuum forming pulls heated sheet over a shape. CUTTING — sawing, milling, laser and CNC removal. FORMING — bending, pressing, drawing without removing material. Each leaves recognisable marks on the product, which is how you can often tell how something was made.
Scale changes everything
ONE-OFF: hand tools, high skill, high unit cost. BATCH: jigs and templates, moderate setup. MASS: dedicated tooling, very low unit cost, enormous setup cost. CONTINUOUS: runs constantly, for materials like glass or steel. The same product designed for one-off and for mass production looks different.
Tooling drives design
An injection mould can cost tens of thousands to make and then produce parts for pennies. That is why mass-produced parts are designed to come out of a mould cleanly — draft angles, no undercuts, uniform wall thickness. The economics of the tool shape the object, and once you know that you can read it in almost anything plastic in the room.
An injection mould costs £8,000 to make, then 20p a unit. 3D printing costs nothing to set up and £4 a unit. TEN UNITS: mould £8,002 total (£800 each); printing £40. Printing wins overwhelmingly. TEN THOUSAND: mould £10,000 (£1 each); printing £40,000. The mould wins by four to one. The crossover is around 2,100 units — and that number, not the process, is what the designer needs to know.