The shape and size of gates in injection molds have great influence on the quality of plastic parts, so we usually use small gates in injection molds.
1) Small gates can increase the flow rate of material through. There is a large pressure difference between the two ends of the small gate, which can reduce the apparent viscosity of the melt and make it easy to fill the mold.
2) The small gate can increase the temperature of the melt and increase the fluidity. The friction resistance at the small gate is large, when the melt passes through the gate, part of the energy is transformed into friction heat and heats up, which is good for improving the quality of thin-walled plastic parts or plastic parts with fine patterns.
3) Small gates can control and shorten the time of replenishment, reduce the internal stress of plastic parts and shorten the molding cycle. In the injection, the pressure-holding stage continues until the condensation at the gate. The small gate condenses quickly and the replenishment time is short, which reduces the condensation orientation and condensation strain of the macromolecule and greatly reduces the internal stress of the replenishment. The adaptation of small gates to closure can also correctly control the replenishment time and improve the quality of plastic parts.
4) The small gate can balance the feed rate of each cavity. Only after the flow channel is full and has enough pressure, the cavities can be filled with similar time, which can improve the imbalance of the feeding speed of each cavity.
5) Easy to trim the plastic parts. Small gates can be quickly removed by hand. Small gates leave small traces after removal, which reduces the trimming time. However, too small gate will greatly increase the flow resistance and prolong the mold filling time. The melt with high viscosity and the melt with small effect of shear rate on apparent viscosity should not be used.
Post time: Aug-24-2022