Molds & Tooling
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Wall thickness >5mm thick-walled products have prominent sink marks and bubble problems
Problem Phenomenon
Wall thickness >5mm thick-walled products have prominent sink marks and bubble problems
Cause Analysis
Thick walls have long cooling time, internal cooling slow, outer layer solidifies first, internal shrinkage sink marks
Holding pressure time insufficient, thick wall center not compacted
Gate too small, holding pressure cannot be transmitted to the thick wall center
Bubbles and voids inside thick walls
Cellulose acetate butyrate shrinkage rate 0.4-0.6%, thick wall shrinkage more obvious
Solution
Extend holding pressure time to ensure thick walls are fully compensated for shrinkage
Increase gate size, extend gate freezing time
Lower the mold temperature to accelerate outer layer cooling of thick walls
Extend overall cooling time
Avoid excessively thick wall thickness in design
Key Takeaway
Thick walls require extended holding pressure and cooling time
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