It is the channel connecting the main runner (or branch runner) and the cavity. The cross-sectional area of the channel can be equal to the main flow channel (or branch channel), but it is usually reduced. So it is the smallest cross-sectional area in the entire runner system. The shape and size of the gate have a great influence on the quality of the product. The function of the gate is: A. Control the material flow speed: B. Prevent backflow due to the early solidification of the melt stored in this part during injection: C. Make the passing melt subject to strong shear and increase the temperature , Thereby reducing the apparent viscosity to improve fluidity: D, to facilitate the separation of the product and the runner system. The design of the gate shape, size and position depends on the nature of the plastic, the size and structure of the product. Generally, the cross-sectional shape of the gate is rectangular or circular, and the cross-sectional area should be small and the length should be short. This is not only based on the above effects, but also because it is easier for small gates to become larger, and it is difficult for large gates to shrink. The gate location should generally be selected where the product is thickest without affecting the appearance. The design of the gate size should take into account the properties of the plastic melt.
