Injection Molding
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PPO Sink Marks and Compensation
Problem Phenomenon
[Problem Phenomenon] Sink marks on the back of thick-walled ribs of PPO products; holding pressure adjustment effect is inconsistent
Cause Analysis
Insufficient holding pressure (below 40% of injection pressure) or insufficient holding time makes compensation inadequate; premature gate freeze cuts off the compensation channel; during on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based only on experience
Solution
Set holding pressure at 40-60% of injection pressure and extend the time; reduce material or strengthen cooling in thick-walled areas; enlarge the gate to delay freezing; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
For PPO sink marks first check holding pressure ratio and time, then check gate freezing; 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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