Extrusion & Post
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TPU extrusion melt fracture
Problem Phenomenon
Sharkskin-like lines appear on the surface of the extrudate.
Cause Analysis
Melt fracture occurs when the shear rate of the melt through the die is too high; low temperature and small gaps aggravate it; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
①increase die temperature; ②widen the die gap; ③reduce extrusion speed; ④evaluate processing aids; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Melt fracture is a manifestation of shear instability; temperature and gap adjustment can alleviate it; 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 later
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