Molds & Tooling
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PP Dimensional Deviation
Problem Phenomenon
【Problem Phenomenon】PP product dimensions drift and are unstable between batches
Cause Analysis
The shrinkage rate range is wide (1.0-2.5%) and is affected by mold temperature, holding pressure and crystallization; post-crystallization also makes dimensions change over time; during on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
Lock mold temperature and holding pressure; modify the mold according to measured shrinkage; consider post-crystallization aging; SPC monitoring; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PP dimensions are affected by crystallization and post-crystallization, lock the process plus SPC; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for similar problems in the future
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