Molds & Tooling
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ABS ejection whitening (stress whitening)
Problem Phenomenon
White round spots or radial white marks appear at ejector pin positions, obvious on dark-colored parts, affecting appearance.
Cause Analysis
During ejection, the product is locally sheared beyond yield, producing stress whitening; too large ejection force, insufficient product cooling, small draft angle, or small ejector pin area are the inducements, related to ABS's high rigidity and large gripping force.
Solution
①Extend the cooling time to lower the ejection temperature; ②increase the ejector pin cross-sectional area and the number of ejector pins to disperse the force; ③reduce the holding pressure to reduce the gripping force; ④polish the cavity around the ejector pins; ⑤optimize the ejector pin layout to areas of high rigidity.
Key Takeaway
ABS ejection whitening=an alarm of 'ejection force exceeding the standard': disperse the ejection force, give sufficient cooling, and reduce the gripping force to eliminate it; the ejection whitening position is the ejector pin position, and following it to find the cause is the fastest.
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