Extrusion & Post
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PET sheet warpage
Problem Phenomenon
PET sheet edges curl up and become uneven after winding
Cause Analysis
Uneven cooling of the three rolls causes crystallinity differences between the two sides of the sheet; residual stress causes warpage; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
Recalibrate the three-roll temperature gradient; balance cooling on both sides of the sheet; add cooling rolls before winding; 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
Sheet warpage is a manifestation of uneven cooling on both sides; after confirming effectiveness, fix 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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