Molds & Tooling
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COC Obvious Ejector Pin Marks
Problem Phenomenon
Circular marks are visible at the ejector pin positions of COC transparent parts, obvious under side light, optical parts are judged defective, and marks remain even after increasing the number of ejector pins.
Cause Analysis
The product temperature is too high at ejection, and the ejector pin pressure causes microscopic deformation of the surface layer leaving marks; the mold temperature in the ejector pin area is too high and cooling is uneven; excessive ejection speed impacts the surface.
Solution
①Extend cooling to lower the ejection temperature; ②strengthen local cooling in the ejector pin area; ③soft-start the ejection speed; ④arrange ejector pins away from optical functional areas and increase the ejection area.
Key Takeaway
COC ejector pin marks are the combined result of temperature and pressure; the ejection design of optical parts should prioritize function; local cooling enhancement is the most direct process means.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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