A combined plastic mold used for compression molding, extrusion molding, injection molding, blow molding and low foaming molding mainly includes a concave mold with a variable cavity composed of a concave mold composite substrate, a concave mold component and a concave mold composite clamp, and a convex mold with a variable core composed of a convex mold composite substrate, a convex mold component, a convex mold composite clamp, a cavity cutting component and a side cutting composite plate. Coordinated change of die convex, concave and auxiliary molding system. It can process series plastic parts of different shapes and sizes. The plastic processing industry is equipped with plastic molding machines, which endow plastic products with complete configuration and precise dimensions. Due to the wide variety of plastics and processing methods, and the complex and simple structure of plastic molding machines and plastic products, the types and structures of plastic molds are also diverse. With the rapid development of the plastic industry and the continuous improvement of the strength of general and engineering plastics, the application range of plastic products is also expanding, and the consumption of plastic products is also rising.
　　Plastic mold is a tool for producing plastic products. It is composed of several groups of parts, and this combination has a molding cavity. During injection molding, the mold is clamped on the injection molding machine, the molten plastic is injected into the mold cavity, cooled and shaped in the cavity, and then the upper and lower molds are separated. The products are ejected from the mold cavity through the ejection system, and finally the mold is closed for the next injection. The whole injection process is carried out in a circular way.
　　Generally, plastic mold is composed of two parts: moving mold and fixed mold. The moving mold is installed on the moving template of the injection molding machine, and the fixed mold is installed on the fixed template of the injection molding machine. During injection molding, the movable mold and the fixed mold are closed to form the gating system and cavity. During mold opening, the movable mold and the fixed mold are separated to take out the plastic products.
　　Although the structure of the mold may vary greatly due to the variety and performance of plastics, the shape and structure of plastic products and the type of injection machine, the basic structure is the same. The mold is mainly composed of gating system, temperature regulating system, molding parts and structural parts. The gating system and molding parts are the parts in direct contact with plastics and change with plastics and products. They are the most complex and most variable parts in plastic mold, requiring the highest processing finish and precision.
　　The gating system refers to the part of the runner before the plastic enters the mold cavity from the nozzle, including the main runner, the cold cavity, the diverter and the gate. Formed parts refer to various parts that form the shape of the product, including moving mold, fixed mold and cavity, core, molding rod and exhaust port. Driven by high technology and the application demand of pillar industries, China's plastic mold has formed a huge industrial chain. From the upstream raw and auxiliary materials industry and processing, testing equipment to the downstream machinery, automobile, motorcycle, home appliances, electronic communications, building materials and other major application industries, plastic mold has developed a vitality.