Molding Process
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PMMA Shrinkage Rate 0.4-0.8%
Problem Phenomenon
Product dimensional deviation, difficult filling at overly thin wall sections, high dimensional stability requirements
Cause Analysis
PMMA shrinkage rate is relatively low, about 0.4-0.8% varying by grade; however, wall thickness designs less than 1mm should be avoided, as thin walls are difficult to fill and concentrate stress
Solution
①Add allowance in the mold for 0.4-0.8% shrinkage; ②design wall thickness not less than 1mm; ③conduct dimensional inspection in the stable state after stress release; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability
Key Takeaway
PMMA's small shrinkage is its dimensional advantage; the 1mm wall thickness lower limit and stable-state inspection are two boundaries of precision design; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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