Drift, not defects
Most extrusion problems are not bad parts, they are parts that slowly moved. A die wears, a cure time shifts, a batch of compound behaves slightly differently. Each change is small enough to pass a spot check and large enough to fail in your assembly.
Check 1 - incoming compound
The compound is qualified before it enters production and the mix is recorded. Without that record a batch cannot be traced back, and a field failure becomes an argument instead of an investigation.
Check 2 - in-process dimensions
Dimensions are checked during the run, not only at the end. A drift caught early costs a few metres; the same drift caught at packing costs the whole reel. This is the single check that separates a supplier who measures from one who describes.
Check 3 - cure state
Under-cured material keeps changing shape after it leaves the line. That is how a part that measured correctly at dispatch ends up loose a season later. Cure state is verified before the profile is cut.
Check 4 - pre-shipment inspection
Hardness, colour, surface condition and dimensions are inspected before packing, and the record travels with the batch. Ask for it with your order. A supplier comfortable with its process will send it without being asked twice.
What to ask for
Three things: the first-article measurement, the per-batch inspection record, and what happens when a check fails. The third answer tells you more about the supplier than the first two combined.
Profiles for this application
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