The choice of manufacturing technique depends mainly on cost, scale of production, and material. These factors interact: the most technically suitable process may not be economically viable at the required production volume.
The Reasoning
A manufacturer compares the process's initial investment with its cost per product. Total production cost can be represented as:
Processes requiring expensive moulds, dies, or automated machinery have high fixed costs but may achieve low unit costs at large scales. More flexible techniques often have lower setup costs but higher variable costs because they require more labour or processing time.
| Factor | Influence on technique | Example |
|---|---|---|
| Cost | Tooling, machinery, labour, energy, maintenance, and material waste affect economic viability. | Injection moulding has expensive tooling but a low unit cost at high volumes. |
| Scale | One-off and small-batch production favour flexible processes; mass production justifies specialized tooling and automation. | CNC machining may suit a small batch, while injection moulding suits mass production. |
| Material | Material properties such as melting point, hardness, ductility, viscosity, and thermal stability determine process compatibility. | Thermoplastics can be injection moulded because they soften when heated; timber cannot be processed this way. |
For example, producing ten customized aluminium housings may favour CNC machining because no dedicated mould is needed. Producing one million identical thermoplastic housings is more likely to justify injection moulding: the tooling cost is distributed across many units, creating economies of scale.
A common misconception is that the cheapest technique is always best. The correct choice must also satisfy the material requirements, required quantity, tolerances, quality standards, and desired production rate.
Exam Technique
For IB Design Technology B4.1, do not merely list cost, scale, and material. Explain how they interact, recommend a suitable manufacturing technique for the stated context, and justify it using process characteristics such as setup cost, production volume, material compatibility, and unit cost.
