Molds & Tooling
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PMMA Ejection Drag Marks and Whitening
Problem Phenomenon
Drag scratches and stress whitening appear in the ejection area of products; damage is especially obvious on high-polish surfaces.
Cause Analysis
Insufficient draft angle or excessive ejection force causes hard friction between product and cavity during ejection; PMMA has high surface hardness but is brittle, and whitens wherever stress concentrates.; During on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based on experience alone.
Solution
①Draft angle ≥1°, 1.5~2° for complex parts; ②balanced ejection, increase ejection area; ③polish cavity to reduce friction; ④extend cooling to improve demolding strength.
Key Takeaway
Ejection damage destroys PMMA's surface and optical quality; draft angle, polishing and ejection balance are the three design essentials, and whitened parts should not be downgraded for use.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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