Manufacturing Processes and Techniques
Shaping and joining
Know material-removal processes (sawing, drilling, turning, milling, filing), forming processes (bending, casting, vacuum forming, injection moulding, extrusion) and joining methods. Permanent joints include welding, brazing, soldering, riveting and adhesives; temporary or semi-permanent joints include screws, bolts, nuts and knock-down fittings. Wood joints include butt, lap, mortise and tenon, dovetail and dowel. A common trap is choosing a joint that cannot resist the applied load, such as a butt joint for a chair leg.
Scale of production
Distinguish one-off, batch, mass and continuous production, and link each to its tooling costs, labour costs and unit cost. Jigs and fixtures improve accuracy and repeatability in batch work. CAD/CAM, CNC machines and laser cutters suit complex or repeated shapes but carry high set-up costs, so they are uneconomic for a single item.
Finishing and quality
Understand surface preparation, then finishes: paint, varnish, oil, stain, galvanising, powder coating and anodising. Quality control uses go/no-go gauges, templates and inspection against the specification. Tolerances state the permitted variation in a dimension.
Worked example: choosing a process
A school needs 200 identical acrylic key rings. Cutting each by hand is slow and inconsistent. Laser cutting from a CAD file gives accurate, repeatable edges and needs no mould, so it suits this batch size. Injection moulding would be cheaper per unit at very large volumes but the mould cost is unjustified here.
Rule of thumb
Choose the process by volume, required accuracy, material and available equipment, and always state the reason.