Manufacturing and Production Processes
Scale decides the process
Know the four scales: one-off, batch, mass, and continuous. For each, be able to state the tooling cost, unit cost, labour skill, and flexibility trade-off. High tooling cost (dies, moulds, jigs) is only justified by volume; that single idea answers many questions.
Processes to name accurately
- Metals: casting, forging, rolling, extrusion, punching and blanking, bending, turning, milling, welding, brazing.
- Polymers: injection moulding, blow moulding, vacuum forming, extrusion, rotational moulding, compression moulding for thermosets.
- Timber: sawing, planing, jointing (mortise and tenon, dovetail, dowel), laminating, veneering.
- Joining and finishing: adhesives, fasteners, welding, and surface preparation before any finish.
Also know jigs and fixtures (a jig guides the tool; a fixture holds the work), tolerance and fit, and quality control versus quality assurance.
Traps that appear in questions
- Naming a process without justifying it. Say why: shape complexity, wall thickness, undercuts, volume, material.
- Ignoring draft angles and undercuts in moulding answers.
- Confusing jig and fixture.
- Treating CAD/CAM and CNC as the same thing. CAD creates geometry; CAM converts it to toolpaths; CNC executes them.
- Forgetting safety and waste in process descriptions.
Worked example
A school needs 500 identical storage tubs. Rule of thumb: at 500 units, injection moulding tooling is hard to justify, so vacuum forming over a pattern or rotational moulding may suit better. Justify by volume, tooling cost, wall uniformity, and required finish - and state the limitation (vacuum forming gives poor detail on the underside).