Molds & Tooling
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POM insufficient draft scratching
Problem Phenomenon
Scratch streaks and ejector whitening marks appear on the product surface after demolding, especially severe for deep-cavity thin-walled parts.
Cause Analysis
POM has large shrinkage and high hardness; after gripping the core, if the draft is less than 1.5~3°, hard friction between the product and the cavity during ejection produces scratching and stress whitening.
Solution
①Increase the draft to 1.5~3°; ②increase the ejection area and balance the ejector pin arrangement; ③polish the cavity to reduce friction; ④use release agent as a transition if necessary.
Key Takeaway
Scratching caused by insufficient draft continues to worsen with mold wear; reserving sufficient draft at the new mold design stage costs far less than repairing the mold afterward.; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence
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