Molds & Tooling
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PC Ejector Whitening and Ejector Cracking
Problem Phenomenon
Whitening or cracks appear at ejector pin positions, white spots are obvious on transparent parts, high incidence on deep-cavity parts.
Cause Analysis
PC has large rigidity and large gripping force; concentrated ejection force causes stress whitening and even ejector cracking; insufficient cooling, small draft angle, and excessive holding pressure all aggravate it; PC's brittleness makes it sensitive to concentrated ejection force.
Solution
①Extend cooling time to fully shape the product; ②Increase the number and area of ejector pins or switch to a stripper plate; ③Reduce holding pressure; ④Ensure sufficient draft angle and polish; ⑤Arrange ejection points at high-rigidity locations.
Key Takeaway
PC ejector whitening and cracking = 'large gripping force + concentrated force': first disperse the ejection force, then extend cooling, and finally reduce holding pressure; PC is both rigid and brittle, and the design margin of the ejection system must be larger than for general-purpose materials.
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