Extrusion & Post
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HDPE Melt Fracture
Problem Phenomenon
HDPE extrusion surface is rough like sharkskin
Cause Analysis
When shear rate exceeds the critical value, melt fracture occurs and the surface becomes periodically rough; during on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based solely on experience; this mechanism has been repeatedly verified by industry data and should be confirmed first during troubleshooting
Solution
Reduce line speed; increase melt temperature; polish die lip flow channel; add PPA additive; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability; change only one variable at a time and record parameter changes to facilitate locating effective measures
Key Takeaway
Melt fracture is treated by reducing speed, increasing temperature, and adding PPA; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a reference for troubleshooting similar problems in the future
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