Molds & Tooling
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PA6 Black Speck Carbonization Troubleshooting
Problem Phenomenon
Black specks randomly appear in light-colored PA6 products, with unknown source
Cause Analysis
Material accumulated in dead corners of the barrel and nozzle is carbonized under long-term heating and falls off; hot runner dead corners and material hidden in screw wear gaps are common sources of black specks, and incomplete material change also introduces them; during on-site troubleshooting, verify item by item according to this mechanism, avoiding blind machine adjustment based only on experience
Solution
Disassemble and clean the screw and nozzle to remove carbonized material in dead corners; check hot runner dead corners; use purging compound transition in the cleaning procedure; when black specks appear concentratedly, stop the machine for thorough cleaning; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Black speck troubleshooting cleans and verifies item by item in the order of barrel, nozzle and hot runner; 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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