Molds & Tooling
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POM product dimensions too small (post-shrinkage)
Problem Phenomenon
Measurement at demolding is acceptable, but after 24 hours the dimensions continue to shrink out of tolerance.
Cause Analysis
POM has high crystallinity (shrinkage can reach more than 2%), continues to crystallize and shrink after demolding, with obvious changes within 24 hours; measuring too early gives a false pass.
Solution
①Place products at constant temperature for 24 hours before inspection; ②compensate the mold for a shrinkage of about 2% or more and correct according to actual measurement; ③unify measurement aging; ④anneal for stabilization if necessary.
Key Takeaway
POM dimensions = only the dimensions after 24 hours count.
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