Molds & Tooling
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Obvious depressions at thick-wall areas of the product (rib roots, back of bosses)
Problem Phenomenon
Obvious depressions at thick-wall areas of the product (rib roots, back of bosses), uneven surface, especially obvious under side light
Cause Analysis
Holding pressure insufficient or holding time short
Gate too small, freezing too early, holding pressure cannot be transmitted
Uneven wall thickness, thick-wall areas cool slowly and shrink more
Mold temperature on the high side (exceeding the 40-80°C upper limit), slow cooling
Melt temperature too high, large volume shrinkage
Solution
Increase holding pressure 80-120MPa, hold 15-30s
Increase gate cross-sectional area, gate thickness ≥60% of wall thickness
Lower mold temperature to the low side of 40-80°C to accelerate cooling
Appropriately lower barrel temperature to reduce volume shrinkage
Optimize wall thickness design to reduce abrupt changes
Key Takeaway
Shrinkage depressions need improvement from the three aspects of holding pressure, gate and mold temperature
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