Injection Molding
12 görüntüleme
Gate freezing too fast in random copolymer polypropylene injection mold
Sorun Belirtisi
The gate solidifies prematurely during holding pressure, holding pressure cannot be transmitted into the cavity, and shrinkage cavities or depressions appear in thick-wall areas of the product.
Gate freezing time is shorter than holding time, resulting in insufficient shrinkage compensation.
Neden Analizi
(1) Gate size is too small; the cross-sectional area is insufficient to maintain the melt channel
(2) Mold temperature is on the low side; the gate area cools too fast
(3) Melt temperature is on the low side; melt viscosity at the gate is high and solidifies quickly
(4) Improper gate shape design, such as a pinpoint gate with too small a diameter
(5) Holding pressure is set too low, and melt flow driving force is insufficient
Çözüm
(1) Increase gate size; gate thickness is at least 60-70% of product wall thickness
(2) Appropriately increase mold temperature to the higher value within the 40-80°C range
(3) Appropriately increase melt temperature to the higher value within the 190-260°C range
(4) Optimize gate shape, avoiding too-small pinpoint gates, and switch to side gates or fan gates
(5) Increase holding pressure to increase the driving force of melt through the gate
Temel Çıkarım
Gate freezing too fast is caused by small gate size or low temperature; freezing time needs to be extended by enlarging the gate and increasing temperature.
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