Processing Machinery
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POM Black Speck and Yellow Streak Troubleshooting
Problem Phenomenon
Black specks and brown-yellow streaks appear on parts; after cleaning the barrel, improvement is short-lived and the problem recurs
Cause Analysis
Black specks and yellow streaks originate from thermal decomposition of stagnant material: dead spots in the barrel and nozzle, too small shot-to-capacity ratio, and poor hopper cooling all form stagnation points; periodic release forms intermittent defects
Solution
①Reduce residence time or switch to a smaller injection unit; ②troubleshoot dead spots in the barrel, screw, and nozzle; ③check hopper cooling to maintain 80-90℃; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
POM black specks and yellow streaks are the signature of stagnation points; dead-spot troubleshooting plus shot-ratio management structurally eliminates the recurrence source; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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