Material Drying
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PC regrind moisture content out of control
Problem Phenomenon
After mixing in sprue and runner material, silver streaks and bubbles increase significantly, and the higher the ratio, the more severe the defects
Cause Analysis
Sprue and runner material has a large specific surface area and absorbs moisture faster, and after experiencing one heat history the molecular weight has already decreased; secondary moisture absorption and hydrolysis further aggravate degradation, and defects amplify with the regrind ratio
Solution
①Regrind ratio controlled within 20%; ②Regrind is fully dried separately before blending; ③Regrind is used promptly after crushing to avoid moisture absorption and contamination from open storage；After adjustment, take continuous samples to verify the effect, and resume mass production only after confirming stability
Key Takeaway
Regrind management is the weak link of the PC drying system; controlling ratio, re-drying, and preventing contamination together can stabilize quality；After confirming effectiveness, solidify the parameters and practices into the work instruction to prevent recurrence
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