Processing Machinery
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PVC Residence Time Management
Problem Phenomenon
Small products produced on large machines, first few shots normal, then products gradually discolor and degrade
Cause Analysis
PVC slowly degrades even within processing window: at 170-180℃ can stay 30-45 minutes, at 185-195℃ only 15-20 minutes, above 200℃ 5-10 minutes is high risk; low shot weight ratio inevitably exceeds time
Solution
①Shot weight accounts for 40-75% of barrel capacity; ②Small parts change to small machine; ③Shutdown overtime replace barrel with PE/PP; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Residence time is PVC's second red line besides temperature; 40-75% shot ratio plus replacement procedure, neither can be omitted; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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