Injection Molding
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Gate freezes too fast in general-purpose polyethylene injection mold
Problem Phenomenon
During the holding process, the gate solidifies too early, the holding pressure cannot be transmitted to the inside of the cavity, and shrinkage cavities or depressions appear in the thick-walled parts of the product.
The gate freezing time is shorter than the holding time, and the feeding is insufficient.
Cause Analysis
（1）The gate size is too small, and the cross-sectional area is insufficient to maintain the melt channel
（2）The mold temperature is low, and the gate area cools too fast
（3）The melt temperature is low, and the melt viscosity at the gate is high and solidifies rapidly
（4）The gate shape is improperly designed, such as the pin-point gate diameter being too small
（5）The holding pressure is set too low, and the melt flow driving force is insufficient
Solution
（1）Increase the gate size, the gate thickness should be at least 60-70% of the product wall thickness
（2）Appropriately raise the mold temperature to the higher value within the range of 30-80°C
（3）Appropriately raise the melt temperature to the higher value within the range of 160-260°C
（4）Optimize the gate shape, avoid excessively small pin-point gates, and use side gates or fan gates instead
（5）Increase the holding pressure to increase the driving force of the melt through the gate
Key Takeaway
Gate freezing too fast is caused by small gate size or low temperature, and the freezing time needs to be extended by enlarging the gate and raising the temperature.
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