Injection Molding
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Excessively Fast Gate Freezing in High-Density Polyethylene Injection Molds
Fenómeno do problema
During the holding pressure process, the gate solidifies prematurely, 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 pressure time, and the shrinkage compensation is insufficient.
Análise das causas
（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 at the gate has a high viscosity 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
Solução
（1）Increase the gate size, with the gate thickness being at least 60-70% of the product wall thickness
（2）Appropriately increase the mold temperature to a higher value within the 30-80°C range
（3）Appropriately increase the melt temperature to a higher value within the 180-260°C range
（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
Conclusão principal
Excessively fast gate freezing is caused by small gate size or low temperature, and the freezing time needs to be extended by enlarging the gate and increasing the temperature.
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