CAD/CAM benefits: extreme accuracy, repeatable, no human fatigue errors, complex shapes, direct from design to manufacture.
Tolerances and prototyping
CNC machines hold tolerances of ±0.01mm or better. Hand manufacturing typically ±0.5mm.
Tighter tolerance = higher cost and longer manufacturing time.
Set tolerance as loose as the function allows while ensuring correct fit.
Rapid prototyping — 3D print or laser cut cardboard model quickly from CAD file to test before committing to tooling.
3D print pros: no tooling cost, any geometry, fast. Cons: slow for high volumes, layer lines, limited materials.
Injection mould pros: fast per unit, excellent surface finish. Cons: high tooling cost (£1,000s–£100,000s).
Exam questions — 3 questions · 9 marks · real AQA 8552 past papers
Extended questions included — read the hint. AI marks against the AQA 8552 mark scheme.
1 markCNC advantage for batch partsAQA 8552 style
What is the main advantage of CNC manufacturing over hand manufacture for producing 1000 identical brackets?
A CNC uses fewer materials making it more sustainable
B CNC produces each part to exactly the same dimensions consistently — every part in the batch is identical regardless of operator fatigue or variation
C CNC machines are always cheaper than skilled workers
D CNC can only work with metals
4 marks3D printing vs injection mouldingAQA 8552 style
A product designer needs 10 prototype parts immediately, and later 50,000 production parts. Evaluate 3D printing and injection moulding for each situation and recommend in each case. (4 marks)
Hint: Two scenarios, two recommendations. 10 prototypes: 3D print (no tooling, fast). 50,000 production: injection mould (low unit cost at scale). Give clear reasoning for each.
+40 XP
1 markRapid prototyping purposeAQA 8552 style
Why do designers use rapid prototyping early in the design process?
A To produce the final product quickly before the client deadline
B To quickly produce a physical model for testing and user evaluation before committing to expensive production tooling
C Because rapid prototypes are stronger and more accurate than the final product
D To generate the working drawings required for manufacture
2 marksTolerances in CNC assemblyAQA 8552 style
Explain why setting the correct tolerance is important for a CNC-machined part that must fit into a larger assembly. (2 marks)
Hint: Too loose → rattles/fails. Too tight → won't fit/expensive. And: tighter = more expensive — so set as loose as function permits.