Structure and composition of injection mold

　　The structure of the injection mold is determined by the complexity of the plastic part and the structural form of the injection machine. Its basic structure is composed of two parts: dynamic mold and fixed mold. The fixed mold part is installed on the fixed template of the injection machine, and the movable mold part is installed on the movable template of the injection machine. In the process of injection molding, the dynamic mold part moves with the closing system of the injection machine. Meanwhile, the dynamic mold part and the fixed mold part are guided by the guide column to form the pouring system and the mold cavity. The plastic melt enters the mold cavity from the injection machine nozzle through the pouring system. When the mold is cooled and opened, the dynamic mold part and the fixed mold part are separated and the plastic parts are taken out.

　　According to the function of each part of the mold, the injection mold is composed of molding parts, structural parts, pouring system, temperature regulation system and exhaust system, as shown in Figure 4-1.

　　1. Formed parts

　　Refers to the parts that make up the cavity. Such as: punch (core), die, insert and insert, etc. The punch (core) forms the shape of the inner surface of the plastic part, and the die (cavity) forms the shape of the outer surface of the plastic part. After the die is closed, the punch and the die form the cavity of the die. In the mold as shown in Figure 4-1, the cavity is composed of moving template 1, fixed template 2, punch 7, etc.

　　2. Structural parts

　　Refers to mold base, mechanism, etc. Mold base, such as: upper and lower mold bases, supporting parts, etc.; mechanism, such as: mold closing guide mechanism, pushing mechanism, side core pulling mechanism, etc.

　　The supporting parts are used to prevent the deformation of the forming parts and the mechanisms under the forming pressure. The supporting parts of the mould mainly include: supporting block (cushion block), supporting plate (movable mould base plate), supporting block, supporting plate, supporting column (movable mould pillar), etc. The closing guide mechanism is to ensure that the moving die and the fixed die are correctly matched when closing the die. Commonly used are: guide pillar guide mechanism and cone guide mechanism. Push out mechanism refers to the device that pushes the plastic part out of the mold after parting. Common: push rod push out, push tube push out, push plate push out, die push out, sequential push out and other mechanisms. The side parting and core pulling mechanism is a device that when the side wall of the plastic part has a concave convex shape, the module or core with the concave convex shape is separated from the plastic part or pulled out before the mold is opened.

　　3. Pouring system

　　The channel through which the molten plastic enters the mold cavity from the injection machine nozzle is called the pouring system, which is composed of four parts: the main flow channel, the shunt channel, the gate and the cold material hole.

　　4. Temperature regulation system

　　In order to meet the temperature requirements of the injection process on the mold, the temperature of the mold must be controlled, so the mold is often equipped with a cooling or heating temperature regulating system. The cooling system is generally provided with a cooling channel on the mold (3 in Figure 4-1), while the heating system is provided with heating elements inside or around the mold.

　　5. Exhaust system

　　In the process of injection molding, in order to remove the gas from the cavity, the exhaust system is often needed. The exhaust system usually has several exhaust grooves on the parting surface, in addition, the matching clearance between the push rod or movable core of many molds and the template can also play the role of exhaust. The exhaust volume of small plastic parts is not large, so the parting surface can be directly used for exhaust.