Molds & Tooling
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PP Black Speck Degradation
Problem Phenomenon
【Problem Phenomenon】Black specks on light-colored PP products, recur after cleaning
Cause Analysis
Carbonization at barrel dead corners, hot runner material accumulation, regrind contamination, degradation over 280°C; black specks are stubborn; during on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
Clean barrel and hot runner, check dead corners; clean regrind; melt temperature ≤280°C; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability; change only one variable at a time and record parameter changes to facilitate locating effective measures
Key Takeaway
For PP black specks check dead corners and regrind, degradation over 280°C is the root; after confirming effectiveness, fix 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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