Material Drying
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PA6 Bubble Cause Differentiation
Problem Phenomenon
Bubbles appear inside or on the surface of the product, and the effects of drying, holding pressure and temperature adjustments vary
Cause Analysis
Water vapor bubbles are evenly distributed with silver streaks; vacuum voids concentrate in the last-to-solidify zone of thick walls; degradation bubbles are accompanied by yellowing and black specks; the three kinds of bubbles look similar but their causes and countermeasures are completely different
Solution
①First measure the moisture content to rule out water vapor; ②Strengthen holding in the thick-wall zone to eliminate vacuum voids; ③Check melt temperature and residence time to rule out degradation; after adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Classifying and characterizing PA6 bubbles is the premise of rectification; the three routes of water vapor, vacuum and degradation must not be confused, test first before acting; after confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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