Molds & Tooling
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POM product dimensions too small (post-shrinkage)
Fenómeno do problema
Measurement at demolding is acceptable, but after 24 hours the dimensions continue to shrink out of tolerance.
Análise das causas
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.
Solução
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.
Conclusão principal
POM dimensions = only the dimensions after 24 hours count.
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