Molds & Tooling
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POM product dimensions too small
Problem Phenomenon
Product dimensions are systematically too small, assembly is too tight, and dimensions return to within the tolerance band after increasing mold temperature and holding pressure.
Cause Analysis
Too low mold temperature and too fast cooling make POM set early with full crystallization shrinkage; insufficient holding pressure and inadequate feeding make the overall shrinkage exceed the design compensation.; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
①Appropriately increase mold temperature; ②increase holding pressure and time; ③extend holding feeding before cooling; ④recheck the mold shrinkage design value.; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Undersized dimensions are adjusted in the opposite direction to oversized ones; first determine the feeding state before changing parameters, and avoid large simultaneous adjustments of holding pressure and mold temperature introducing new fluctuations.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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