We describe here the method of determining the dimensions of a side gate that is used very frequently in the molds for injection molding. A side gate is the simplest gate design. Since the molded article and the gate are joined, the gate is cut off in a secondary operation. A side gate can make the molten plastic flow into the cavity in a stable manner, and also since it is possible to apply the dwell pressure sufficiently, it is possible to prevent flashes in the mold.

The side gate dimensions are determined in the following two steps.

First Step: Determining the gate depth

First check the wall thickness t (mm) of the molded article.
Next, obtain the plastic resin dependent coefficient n from Table 1.

Table 1

Next, obtain the depth h (mm) of the side gate using the following equation.

h = n ∙ t

Second Step: Determining the gate width

First obtain the surface area A (mm²) of the molded item.
Next, obtain the molding material dependent coefficient n from Table 1.
Finally, obtain the gate width W (mm) from the following equation.

W = n ∙ √A/30