Injection Molding
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TPU product dents and sink marks
Problem Phenomenon
Dents and shrinkage wrinkles appear on the product surface, obvious at thick walls and rib positions.
Cause Analysis
Low injection pressure and insufficient feeding compensation, short injection time; overheated material increases shrinkage; poor venting at the dented area also aggravates sink marks; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
①increase injection pressure and extend injection time; ②appropriately reduce melt temperature; ③set vents at dented areas; ④optimize wall thickness design in thick areas; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
TPU sink marks are adjusted along the two lines of feeding compensation and temperature; structural uniformity is the fundamental solution for thick-walled parts; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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