In order to ensure that the gate cuts off the product part and the runner part, it is very important to maintain a balance of the three forces including “gate strength”, “management force of the runner” and “product retention force”. When opening the mold, if the runner part remains on the fixed side and the product part remains on the movable side, both will be cut off at the gate. If the strength of the gate is too large, or the holding force between the product part and the sub-runner is weak, poor gate cutting will occur.

Generally speaking, the sub-runner is held by the locking pin. Its holding force depends on the shape and size of the locking pin and the temperature of the runner part when the mold is opened. If the size or slope of the locking pin is insufficient, the gate will fall off before being cut. Therefore, instead of increasing the strength of the gate, it is better to increase the retention of the runner.

On the contrary, if the holding force of the runner is too large, the runner cannot be separated from the mold. And the strength and rigidity of the resin will also change with temperature, so it must be adjusted.

The product is maintained by the friction of the side slope, or the sliding core. In this situation, it’s still necessary to reach the gate strength. At this time, it will also be affected by temperature.

In addition, the gate strength will of course be affected by the gate design. If the gate size is too large, the strength will increase. So that the gate will not be easily cut. If there are two templates and a tunnel gate is used, it will also be affected by the gate angle and setting position. If there are three templates and a point gate is used, it will also be affected by the inclination and grinding of the secondary main runner.