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Tooling accuracy, and why it matters more than machine specs
The moulding machine cannot produce a tolerance the tool does not have, which is why tool accuracy is the number that decides a part.
Buyers comparing moulders often compare press tonnage, shot weight and machine brand. None of those determine the dimensional tolerance of the finished part. The tool does. A press with excellent repeatability will faithfully reproduce whatever the tool gives it, including its errors.
Mould machining accuracy of 0.002 to 0.005 mm is the figure worth asking about, and it should be quoted per feature rather than as a single headline. A tool can be extremely accurate on a sealing face and looser on a cosmetic surface, and that is usually the correct engineering decision.
The part tolerance that follows is not the same as the tool tolerance, because material shrinkage and process conditions sit in between. We state both in a quotation: the tool accuracy and the expected part tolerance in the specified material. Quoting only the first is how a supplier appears more precise than it is.
Specifications
| Tool accuracy | 0.002 – 0.005 mm depending on the feature |
|---|---|
| Part tolerance | Depends on material and geometry, quoted separately |
| Ask for | Both figures, not just the tool number |
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Send us a drawing and we will tell you what it will cost to tool
Send the 3D data or the drawing with the annual volume and the material. You will get a tooling cost, a sampling schedule and an opinion on anything in the design that will be difficult to mould.