Material Drying
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PP Bubble and Shrinkage Void
Problem Phenomenon
【Problem Phenomenon】Bubbles or shrinkage voids inside PP products, strength is affected
Cause Analysis
Two types: thick-wall shrinkage voids (high shrinkage and insufficient feeding) and bubbles (moisture or air entrainment); high incidence in thick-wall parts; during on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based only on experience
Solution
Strengthen holding pressure and reduce material for thick-wall shrinkage voids; dry for moisture bubbles; improve venting and reduce speed for entrained air; after adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability; change only one variable at a time and record parameter changes to facilitate locating effective measures
Key Takeaway
PP bubbles and shrinkage voids are divided into two types, holding pressure, drying and venting treat the symptoms; after confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence; include this case in the defect archive as a troubleshooting reference for similar problems in the future
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