Timber: Quality Control
Design & Technology: AQA GCSE, topic 3.8.3
Quality Control Systems: Tolerance
How materials are cut, shaped and formed to a tolerance.
Cutting and shaping
- Materials can be cut to form parts.
- Sometimes those parts need to be identical but this is not always possible.
- If we were to cut each material to size every time there would be mistakes.
- Therefore we introduce a tolerance.
Tolerance
- Tolerance is an acceptable dimension that the piece can be.
- Usually, 1 mm less or more than the specified measurement is tolerated.
- This by no means allows for mismatched products to slip through the net but simply allows products to be checked and tested to see if they are still meeting quality standards.
Go/no go systems
- A go/no go system is a gauge that tests against the tolerances set for a part.
- The test can only be passed if you meet the ‘go’ requirement but fail the ‘no go’ requirement.
Example
- For example, if the dowel fits the specified hole securely (go test) and falls through the slightly larger hole (no go test) then it has passed the test.
- If either of the tests fails then the part needs to be redesigned or remanufactured so it is within the tolerance boundaries.
Commercial Processes
Industry typically uses CNC routing.
CNC
- In industry, more expensive equipment is used to speed up production and increase the accuracy of wood products.
- This is known as CNC routing.
CNC cont.
- CNC stands for computer numerical control and routing is simply the hollowing out of material to create room for slotting materials together or for creating a pattern.
- CNC allows for this to happen using grid coordinates and allows for accuracy every time.
- The fact that the process is automated also helps to bring about speed and some peace of mind.
Advantages
- Once the programming of CNC routing has been learnt then you can have fewer people working on a job or you can increase the number of products made.
Disadvantage
- The only disadvantage is that the initial costs of CNC tooling can be high, but if a company makes this investment they can increase their output considerably.
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