Material Drying
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PMMA Sheet Bubbles (Moisture Type)
Problem Phenomenon
White round bubbles appear inside extruded or injection molded sheets, cavities are visible on sectioning, and they are eliminated after sufficient drying.
Cause Analysis
Moisture in the raw material vaporizes during processing to form bubbles; recycled-material sheets have many impurities and high moisture content, and the bubble occurrence rate is significantly higher than with virgin material.; During on-site troubleshooting, verify item by item according to this mechanism to avoid blindly adjusting the machine based on experience alone.
Solution
①Fully pre-dry at 80~90℃ for 3~4 hours; ②confirm raw material grade and moisture content; ③sealed storage against moisture; ④extend drying in humid seasons.; After adjustment, continuously sample to verify the effect, and resume mass production only after confirming stability.
Key Takeaway
For sheet bubbles, first distinguish the raw material grade before checking the process; recycled material itself carries high risk, and bubbles with virgin material are mostly caused by insufficient drying.; After confirming effectiveness, fix the parameters and practices into the work instruction to prevent recurrence.
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