It is the channel connecting the main channel (or runner) and the cavity. The cross-sectional area of the channel can be equal to the main channel (or runner), but it is usually reduced. So it is the smallest part of the entire runner system. The shape and size of the gate have a great influence on the quality of the product.
The role of the gate is:
A, control the flow rate:
B. In the injection, the early flow of the melt in this part can be prevented to prevent backward flow:
C. The molten material passing through is subjected to strong shearing to increase the temperature, thereby lowering the apparent viscosity to increase the fluidity:
D, to facilitate the separation of products and runner system. The design of the gate shape, size, and location depends on the nature of the plastic, the size and structure of the article. Generally, the shape of the cross section 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-mentioned effect, but also because the small gate is larger and easier, and the large gate is very difficult to reduce. Gate location should generally be selected where the product is thickest without affecting the appearance. Gate size design should take into account the nature of the plastic melt. Cavity It is the space for molding plastic products in the mold. The components that make up the cavity are collectively referred to as molded parts. Each molded part often has a special name. The molded parts that make up the shape of the product are called concave molds (also known as female molds) and constitute the internal shape of the product.
(such as holes, slots, etc.) are called cores or punches (also known as male molds). When designing a molded part, the overall structure of the cavity must first be determined based on the properties of the plastic, the geometry of the product, dimensional tolerances, and usage requirements. The second is to select the parting surface, the location of the gate and the vent hole, and the demoulding method according to the determined structure. Finally, according to the control product size for the design of each part and determine the combination of parts. The plastic melt has a very high pressure when it enters the cavity, so the molded part must be checked for reasonable material selection and strength and stiffness. In order to ensure that the surface of the plastic product is smooth and beautiful and easy to release, the surface with the plastic has a roughness Ra>0.32um, and it must be corrosion-resistant. Molded parts are generally heat treated to increase hardness and are made of corrosion-resistant steel.