Molds & Tooling
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PVC Black Streak Troubleshooting
Problem Phenomenon
Black streaks appeared on PVC products
Cause Analysis
Local retention degradation forms carbonized streaks, commonly at the nozzle, hot runner dead corners or screw wear areas; during on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
Troubleshoot and clean in the order of nozzle, hot runner, screw; stop the machine immediately when black streaks appear; after adjustment, continuously sample to verify the effect, and resume mass production after confirming stability; change only one variable at a time and record parameter changes to facilitate locating effective measures
Key Takeaway
Black streaks are a signal of retention carbonization—stop the machine and troubleshoot immediately; 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 in the future
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