Material Drying
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Product dimensions out of tolerance range
Problem Phenomenon
Product dimensions out of tolerance range, too large or too small, dimensions unstable, fluctuating with batch or time
Cause Analysis
Mold dimension design did not consider cellulose acetate butyrate shrinkage 0.4-0.6%
Unstable injection conditions (pressure/temperature fluctuation)
Raw material moisture variation causing shrinkage differences
Cellulose acetate butyrate dimensional change after moisture absorption (especially obvious for PA types)
Insufficient cooling time, product demolded before fully shrunk
Solution
Precisely design mold dimensions according to 0.4-0.6% shrinkage
Stabilize injection conditions, control temperature and pressure fluctuation
Strictly control raw material moisture
Cellulose acetate butyrate is highly hygroscopic and needs conditioning treatment to stabilize dimensions
Extend cooling time to ensure full shrinkage
Key Takeaway
Dimension out of tolerance requires stable process conditions and moisture control
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