Extrusion & Post
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POM Shrinkage Out of Tolerance
Problem Phenomenon
POM part dimensions are smaller than the drawing and inconsistent between batches
Cause Analysis
POM shrinkage is 1.8-3.5% and is greatly affected by mold temperature and holding pressure; the mold shrinkage value does not match the actual process; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
Measure actual shrinkage to correct the mold; lock mold temperature and holding pressure; SPC monitoring of critical dimensions; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
POM dimensional management is based on measured shrinkage; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for subsequent similar problems
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