Injection Molding
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PMMA Large Gate Design
Problem Phenomenon
After small gate injection, products stress-crack near the gate, and surface shear marks are obvious
Cause Analysis
PMMA's poor flowability requires larger gates to reduce filling resistance; small gates with high shear concentrate stress in the gate area, and shear marks and stress whitening are obvious on transparent parts
Solution
①Enlarge gate size design according to the poor flowability characteristic; ②hot runner systems can be used; ③keep gates away from optical functional surfaces; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PMMA gate design follows the principle of large size to reduce shear; hot runners can be used, but gate position must avoid optical surfaces; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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