Material Drying
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PET dried material storage time limit
Problem Phenomenon
Dried PET chips are used overnight, and the white haze defect rate rises significantly
Cause Analysis
Dried material continuously absorbs moisture during storage, and even in a sealed silo the moisture content rises back to the critical value overnight; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
Use up the dried material within the shift; re-dry overnight material for 2 hours; keep the silo under positive pressure of dry air; after adjustment, take consecutive samples to verify the effect, and resume mass production only after confirming stability; change only one variable at a time and record the parameter changes, so as to locate effective measures
Key Takeaway
Not keeping PET dried material overnight is a basic principle; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for subsequent similar problems
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