Products need a combination of manufacturing techniques because one technique rarely creates every required material, shape, surface, tolerance and connection efficiently. Designers therefore select different processes for individual components and then assemble them into a complete product.
In manufacturing, materials are transformed into components with specified properties and dimensions. Complex products contain parts that perform different functions, so each part may require a different material and manufacturing technique.
For example, a cordless drill may have an injection-moulded polymer casing, machined steel gears, drawn and wound copper wire, an elastomer grip produced by overmoulding, and components joined using screws or adhesives. A surface-finishing process may then improve appearance, corrosion resistance or wear resistance.
| Product requirement | Suitable manufacturing response |
|---|---|
| Complex polymer casing produced in high volume | Injection moulding provides repeatable shapes and a good surface finish. |
| Steel gear requiring dimensional accuracy | Machining achieves precise dimensions and tolerances. |
| Comfortable, non-slip grip | Overmoulding adds a softer elastomer to a rigid casing. |
| Permanent or temporary assembly | Adhesives, welding, screws or snap fits join components appropriately. |
| Improved appearance or durability | Painting, polishing, coating or heat treatment modifies surface properties. |
The selected combination also depends on scale of production, available machinery, labour skills, cost, production time, material properties and required quality. A high initial tooling cost may be justified for mass production, while flexible processes such as computer numerical control machining may be more appropriate for low-volume production.
A common misconception is that using fewer techniques always makes production cheaper. Although simplification can reduce assembly time, forcing every component into one process may increase waste, reduce quality or make the design impossible to manufacture.
For IB Design Technology A4.1, explain the relationship between the product requirement, material and selected technique. In an exam response, use a specific product example and justify why each process is appropriate rather than merely listing manufacturing techniques.