Material Drying
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PPO Silver Streaks and Shear Overheating
Problem Phenomenon
[Problem Phenomenon] Silver streaks still appear on products after PPO drying is qualified, fixed near the gate
Cause Analysis
Shear-overheating-type silver streaks: too-small gate or too-fast injection speed causes melt shear degradation producing volatiles; the cause differs from moisture-type silver streaks and must be distinguished; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
For silver streaks fixed near the gate check shear: enlarge the gate and reduce injection speed; for random silver streaks over the whole surface check moisture; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PPO silver streaks are divided into moisture position and shear position; the location distribution points to the cause; after confirming effectiveness, solidify 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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