Molds & Tooling
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Dimensional drift from PP post-shrinkage
Problem Phenomenon
The product passes the outgoing inspection, but the dimensions become smaller and out of tolerance after storage at the customer.
Cause Analysis
PP crystallization continues after demolding, producing post-shrinkage; high-temperature environments accelerate the post-crystallization process, and premature outgoing inspection leads to missed judgment.; during on-site investigation, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
①Age the product for more than 24 hours before final inspection; ②reserve a post-shrinkage margin in the mold scaling; ③evaluate dimensional stability at the use temperature; ④perform heat aging verification on key parts.
Key Takeaway
PP post-shrinkage is an inherent behavior of crystalline materials; dimensional judgment must allow sufficient aging time, and high-temperature applications also need to evaluate hot-state dimensions.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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