Injection Molding
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POM Holding Pressure Feeding for Thick Walls
Problem Phenomenon
Shrinkage voids appear inside thick-walled parts, with obvious cavities on X-ray inspection and unqualified strength
Cause Analysis
POM's high crystallization shrinkage creates a large feeding demand at the thick-wall center; after the gate freezes, the feeding channel is closed and shrinkage voids form at the center; merely increasing injection pressure cannot solve feeding during the holding stage
Solution
①Extend holding time and increase holding pressure close to injection pressure; ②enlarge the gate to delay freezing; ③prioritize gate placement in thick-walled areas; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Shrinkage voids in thick-walled POM parts are solved by the holding pressure system; sufficient holding time and pressure plus gate channel management are the guarantee of internal quality; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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