Molds & Tooling
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PC Draft Angle and Ejection
Problem Phenomenon
The products are scratched and whitened during demolding, and radial cracks subsequently appear near the ejector pins
Cause Analysis
Insufficient draft angle and unbalanced ejection subject the products to additional mechanical stress, forming high residual stress points in the ejection area; PC is stress-sensitive, and the ejection-damaged areas become crack initiation points
Solution
①Draft angle ≥1°; ②arrange the ejector pins away from high-stress areas and eject with large-area balance; ③polish the mold to reduce friction, and nitride the cavity if necessary; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Mechanical stress in the demolding stage is often overlooked; sufficient draft angle and balanced ejection can eliminate a large category of hidden cracking causes; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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