Molds & Tooling
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PET black speck systematic cleaning
Problem Phenomenon
Black specks repeatedly appear on light-colored PET products and recur shortly after cleaning
Cause Analysis
Black specks originate from carbonized material in dead corners of the barrel and nozzle and from hot runner retention; surface cleaning cannot eradicate them; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
Disassemble and wash the screw, nozzle and hot runner; use purging material in the material change procedure; include the black speck trend in equipment condition monitoring; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Black specks are eradicated by disassembly and washing; trend monitoring prevents recurrence; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a reference for troubleshooting similar problems in the future
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