Molds & Tooling
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Short shot caused by early POM gate freezing
Problem Phenomenon
Thick-walled products have severe sink marks due to insufficient holding pressure, and inspection found that the gate size is small and the freezing time is too early.
Cause Analysis
A small gate cross-section causes it to solidify before the thick zone of the product, so feeding cannot continue during the holding stage; POM crystallizes fast and freezes fast, making the small gate problem more prominent.；During on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
①Enlarge the gate size to delay freezing; ②increase the mold temperature to extend gate open time; ③shorten the runner length; ④set the holding pressure according to the solidification time of the thick zone.；After adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
The gate freezing time determines the effective feeding window; POM should adopt a larger gate design, combined with mold temperature management for holding pressure efficiency.；After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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