Processing Machinery
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PVC Sink Mark
Problem Phenomenon
Sink marks on the surface of thick-wall PVC products
Cause Analysis
Insufficient shrinkage compensation of thick walls; although PVC shrinkage is small, it is still obvious in thick walls; during on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience; this mechanism has been repeatedly verified by industry data and should be confirmed first during troubleshooting
Solution
Increase holding pressure and time; uniform wall thickness design; aim the gate at the thick wall; after adjustment, continuously sample to verify the effect, and resume mass production after confirming stability; change only one variable at a time and record parameter changes to facilitate locating effective measures
Key Takeaway
PVC sink marks are controlled by holding pressure and wall thickness design; 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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