Material Drying
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PPO Dimensional Deviation and Shrinkage
Problem Phenomenon
[Problem Phenomenon] Dimensional deviation of PPO products, inconsistent shrinkage between batches
Cause Analysis
PPO shrinkage of 0.2-0.7% has a small range but is affected by the process; mold temperature fluctuation, holding pressure differences and moisture content changes all alter actual shrinkage; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
Lock mold temperature, holding pressure and drying parameters; correct the mold according to measured shrinkage; establish SPC monitoring of key dimensions; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PPO shrinkage is small but not immune to fluctuation; process locking plus SPC ensures dimensions; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a reference for troubleshooting similar problems in the future
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