Injection Molding
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Ejection whitening of PP injection molded parts
Problem Phenomenon
White marks appear at the ejector pin positions of the product, accompanied by microcracks in severe cases.
Cause Analysis
The ejection force is concentrated or the product ejection temperature is too high, and the local stress exceeds the material yield, producing stress whitening; insufficient draft angle increases the gripping force.; during on-site investigation, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
①Increase the ejector pin area and balance ejection; ②extend cooling to lower the ejection temperature; ③ensure the draft angle; ④increase the mold temperature to reduce gripping.; after adjustment, continuously sample and verify the effect, and resume mass production after confirming stability
Key Takeaway
Ejection whitening is a signal of local stress overload; ejection system optimization and sufficient cooling are the standard countermeasures.; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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