The causes of bubbles in injection moulding products

Update:14 Sep 2018

The plasticizing capacity of the injection moulding mac […]

The plasticizing capacity of the injection moulding machine should be appropriate. If the plasticization is too small, it will not be completely mixed and become brittle. When it is too large, it will degrade. The deformation, bending and twisting of injection moulded products are mainly caused by the fact that the shrinkage rate of the flow direction during plastic moulding is larger than that of the vertical direction, so that the shrinkage ratio of the parts is different and warped, and it is inevitable in the injection moulding. There is a large internal stress remaining inside the piece to cause warpage, which is a manifestation of deformation caused by high stress orientation.

The gas of the bubble (vacuum bubble) is very thin and belongs to the vacuum bubble. In general, if a bubble is found at the moment of mould opening, it is a gas interference problem. The formation of vacuum bubbles is due to insufficient filling or low pressure. Under the rapid cooling of the mould, the fuel at the corner of the cavity is pulled, resulting in a volume loss.


1.Increase the energy of injection: pressure, speed, time and amount of material, and increase the back pressure to make the filling full.

2.Increasing the temperature of the material flow smoothly. Lower the material temperature to reduce shrinkage, and appropriately increase the mould temperature, especially the partial mould temperature at which the vacuum bubble is formed.

3.The gate is placed in the thick part of the part to improve the flow of the nozzle, the runner and the gate, and reduce the consumption of the press.

4.Improve the mould exhaust condition.