Injection Molding
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PVC Injection Flash
Problem Phenomenon
Parting line flash, needs trimming after demolding.
Cause Analysis
Insufficient clamping, excessive pressure; PVC viscosity drops sharply after decomposition making flash easier; parting line wear also induces it; during on-site troubleshooting, verify item by item according to this mechanism, avoid blindly adjusting the machine based solely on experience.
Solution
①Reduce injection/extrusion pressure; ②Calculate and increase clamping force; ③Check whether thermal degradation occurred (yellowing, black specks, odor); ④Repair parting line and moving part fitting clearance, match mold if necessary; ⑤Check parting line and moving part fitting clearance.
Key Takeaway
PVC flash 'also beware of degradation-induced viscosity drop': degradation makes PVC suddenly thin and flash; besides reducing pressure and increasing clamping, check back whether thermal degradation caused abnormal viscosity.
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