Injection Molding
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PC shear rate sensitivity
Problem Phenomenon
【Problem Phenomenon】PC generates heat under high shear, melt degrades and yellows with decreased impact
Cause Analysis
PC is sensitive to shear rate: excessive shear breaks molecular chains causing degradation; both screw rotation speed and injection speed need to be controlled to avoid shear overheating；During on-site troubleshooting, verify item by item according to this mechanism, and avoid blindly adjusting the machine based solely on experience
Solution
Screw rotation speed at medium-low speed; injection speed graded to avoid local high shear; check shear first when yellowing occurs；After adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PC fears high shear, both rotation speed and injection speed must be controlled；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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