Processing Machinery
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PVC Shear Heat Exceeding Standard
Problem Phenomenon
Barrel temperature normal but PVC melt actually overheated and degraded
Cause Analysis
Excessive screw speed and back pressure generate shear heat, actual melt temperature far exceeds setting, forming invisible exceeding; during on-site troubleshooting, verify item by item according to this mechanism, avoid blindly adjusting the machine based solely on experience
Solution
Control screw speed and back pressure to lower limits; measure actual melt temperature; when degradation occurs, check shear heat first; 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
PVC temperature measurement must measure actual melt value, shear heat is the invisible killer; 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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