Material Drying
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Distinguishing PC Bubbles and Vacuum Voids
Problem Phenomenon
Bubbles appear inside or on the surface of the products, visible both in thick-wall areas and near the gate
Cause Analysis
Bubbles formed by moisture vaporization are mostly evenly distributed and accompanied by silver streaks; those formed by insufficient feeding in thick-wall areas are vacuum voids; gas bubbles produced by degradation are accompanied by yellowing and black specks; the causes and countermeasures of the three are different
Solution
①Verify the moisture content to exclude water vapor; ②increase the holding pressure and time in thick-wall areas to eliminate vacuum voids; ③check the melt temperature and residence time to exclude degradation gas; after adjustment, take samples continuously to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Bubble defects must first be classified and characterized; water vapor, vacuum voids and degradation gas correspond to three completely different rectification routes of drying, holding pressure and temperature control; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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