Material Drying
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PVC Injection Silver Streaks
Problem Phenomenon
Surface silver streaks, mostly near gate.
Cause Analysis
Raw material/regrind contains moisture or additives volatilize; shear overheating decomposes gas; PVC is heat-sensitive, shear decomposition also produces gas; during on-site troubleshooting, verify item by item according to this mechanism, avoid blindly adjusting the machine based solely on experience.
Solution
①Dry raw material (especially regrind and fillers); ②Reduce screw speed and back pressure to reduce shear heat; ③Appropriately increase back pressure to help gas discharge and improve mixing uniformity; ④Open or clean vent grooves at corresponding positions to ensure smooth gas discharge; ⑤Control melt temperature within safe window.
Key Takeaway
PVC silver streaks = 'moisture + decomposition gas': besides moisture, PVC silver streaks also have the factor of shear decomposition gas; water control and shear heat control must go together; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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