Question 1

What is the difference between additive and subtractive manufacturing?

Accepted Answer

Additive manufacturing builds objects layer by layer (e.g., 3D printing), adding material only where needed, which reduces waste. Subtractive manufacturing starts with a solid block and removes material (e.g., CNC milling, laser cutting) to create the desired shape. Additive is best for complex geometries and prototypes; subtractive offers higher precision and surface finish for production parts.

Question 2

When should I use injection moulding instead of 3D printing?

Accepted Answer

Use injection moulding for mass production (thousands or millions of parts) because the high initial cost of the metal mould is offset by very low per-unit cost and fast cycle times. 3D printing is better for one-offs or small batches (under 100) where design changes are frequent, as there is no tooling cost and no lead time for moulds.

Question 3

What scale of production is vacuum forming best for?

Accepted Answer

Vacuum forming is typically used for batch production (hundreds to a few thousand parts). It uses a relatively cheap mould (often made from wood or resin), making it cost-effective for medium volumes. For very high volumes, injection moulding is more efficient; for one-offs, 3D printing or hand fabrication may be better.

Question 4

How does the choice of material affect the manufacturing process?

Accepted Answer

Material properties like melting point, strength, and flexibility determine which processes are feasible. For example, thermoplastics can be injection moulded or vacuum formed, but thermosets cannot be remelted. Metals require higher temperatures for casting or forging, while CNC machining works on many materials but is slower for hard metals. Always match the process to the material's behaviour.

Question 5

What is a jig and why is it important in manufacturing?

Accepted Answer

A jig is a custom tool that holds a workpiece and guides the cutting tool to ensure accurate, repeatable positioning. It is crucial in batch and mass production because it reduces setup time, improves consistency, and allows semi-skilled operators to produce high-quality parts. For example, a drill jig ensures holes are drilled in exactly the same place on every part.

Question 6

Can you give an example of a product made by continuous production?

Accepted Answer

Continuous production is used for high-volume, standardised products like paper, steel, or plastic film. For instance, paper is made by a continuous process where wood pulp flows through rollers and dries in a never-ending sheet. This process runs 24/7 and is highly automated, with very low unit costs but huge initial investment.

Systems: Alternative processes that can be used to manufacture components and systems to different scales of production

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