The main categories of manufacturing process - wasting, shaping by casting and moulding, deforming and reforming, fabrication and joining - and how the chosen process depends on material, form and scale.

What this dot point is asking

WJEC wants you to know the main families of manufacturing process, name specific processes within each, describe how a key process works step by step, and explain why a particular process fits a given material, form and production volume. The describe-a-process question (injection moulding is the classic) and the choose-the-right-process question recur every year. You must be able to write an ordered, technically correct account, not just name the process.

The answer

The four process families

Wasting (removing material)

Wasting cuts material away to leave the wanted shape. Examples: sawing, drilling, filing, turning on a lathe (cylindrical parts), milling (flat faces and slots), routing, and laser cutting and CNC machining for precision and automation. Wasting is versatile and accurate but produces offcuts and swarf, so it is wasteful of material.

Casting and moulding

A fluid material is shaped by a mould, then solidifies. Examples:

• Sand casting - molten metal poured into a sand mould made from a pattern; suits one-offs and complex metal shapes (engine blocks, vice bodies).
• Die casting - molten metal forced into a reusable metal die; high volume, good detail.
• Injection moulding - molten thermoplastic forced into a steel mould; very high volume, complex detailed parts.
• Vacuum forming - a heated thermoplastic sheet pulled over a former by a vacuum; open shallow shells (trays, packaging).
• Blow moulding - air inflates molten polymer against a mould; hollow products (bottles).
• Compression moulding - a thermoset charge squeezed and cured in a heated mould.

Deforming and reforming

The material is reshaped without removing or melting all of it. Deforming changes shape while the material stays solid: bending, pressing, forging, drawing, rolling and laminating (gluing thin layers, often around a former, as in plywood and curved chair seats). Reforming changes the material's state (melting and resetting), as in casting and moulding above.

Fabrication and joining

Parts are assembled. Methods include temporary joints (screws, nuts and bolts, knock-down fittings) that allow disassembly, and permanent joints (welding, brazing, soldering, riveting, adhesives, wood joints such as mortise and tenon). Joining lets a product be made from several materials and parts, and the choice affects whether it can be repaired or recycled.

Process depends on scale

Examples in context

Example 1. A laminated curved chair. Thin veneers are glued and clamped around a former and left to cure, so the timber takes and holds a strong curve it could never be cut to without weakening the grain. Lamination is the process that makes the form possible.

Example 2. A cast aluminium saucepan. The body is die cast for a smooth, even-walled shape in volume, then machined (a wasting process) only where a precise mating face for the handle is needed. Real products combine processes, each chosen for what it does best.

Try this

Q1. Name one wasting process and one deforming process, and state what each does to the material. [4 marks]

• Cue. Wasting, for example turning - removes material to leave the shape; deforming, for example bending - reshapes the solid material without removing any.

Q2. Explain why sand casting, not die casting, would be used to make a single prototype engine bracket. [3 marks]

• Cue. Sand casting needs only a cheap pattern and a sand mould, so tooling cost is low and suits one-offs; a die-cast steel die is far too expensive to make for a single part.