Injection Molding
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PA6 Burnt Trapped-Air Treatment
Problem Phenomenon
Black burnt marks repeatedly appear at dead corners of PA6 products, reappearing soon after cleaning the mold
Cause Analysis
Venting at cavity dead corners is poor; at each injection the air is adiabatically compressed and heated, igniting the melt surface, and burnt residue further aggravates local air trapping to form a cycle; during on-site troubleshooting, verify item by item according to this mechanism, avoiding blind machine adjustment based only on experience
Solution
Add venting inserts or venting steel at dead corners; thoroughly clean burnt residue; reduce the final-stage injection speed; use vacuum-assisted venting for stubborn areas; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Burnt is the result of trapped air and adiabatic compression, and venting structure is the radical means; after confirming effectiveness, solidify 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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