Plastic injection mold runner system design

The gate is the connecting part between the runner and the cavity, and is also the end part of the injection mold gating system, the molten plastic enters the cavity and core side through the gate directly. The function of the gate is make the molten plastic coming from the runner enter and fill the cavity with core by fast speed, after the cavity with core are filled with plastic, the gate can be cooled quickly and sealed to prevent the hot material in the cavity from flowing material.

The gate design is related to factors such as the part shape, the cross-sectional size of the part, the plastic performance, the mold structure and the injection process parameters. The gate cross-sectio should be small and the length should be short, so as to increase the material flow speed, fast cooling and sealing to separate the plastic parts, and the gate marks are not obvious.

The gate is a key part of the gating system, the gate location, type and size have a big influence on the plastic parts quality, the quality defects of plastic parts, such as air trapping, shrinkage, water trapping, decomposition, washout, deformation, etc., are often caused by unreasonable gate design. The gate is the smallest part of the entire gating system (except for the direct gate of the sprue type) in many cases.

The design content of the gate includes the following 3 points:

①Select the gate location

②Determine the gate type

③Determine the gate size

We will talk about how to determine the location of the gate in following article.