Plastic molds are tools used for molding plastic products. They enable mass production by imparting specific shapes and precise dimensions to plastics, and are widely applied in automotive, home appliance, electronics and other fields. Their core structure includes the moving mold, fixed mold, as well as gating, temperature control, ejection and other systems. The molding processes are categorized into six types: injection molding, compression molding, extrusion molding, blow molding, thermoforming and high-expanded polystyrene molding.
Molds are adapted to different materials based on process differences: injection molds are suitable for complex thermoplastic products; compression molds are mostly used for thermosetting plastics; while extrusion molds produce continuous profiles such as pipes. Mold materials need to have heat resistance, wear resistance and high polishability. Carbon tool steel or alloy steel are commonly used. For corrosive plastics (e.g., PVC, ABS), corrosion-resistant steels such as martensitic stainless steel are adopted. During the design phase, considerations must be given to the precision of the parting surface, tolerances of structural components and optimization of the gating system. Computer-aided technologies are leveraged to improve the efficiency of matching molding machine parameters.
A modular plastic mold used for compression molding, extrusion molding, injection molding, blow molding and low-expanded molding mainly consists of a female mold with a variable cavity (composed of a female mold assembly base plate, female mold components and female mold assembly clamping plates) and a male mold with a variable core (composed of a male mold assembly base plate, male mold components, male mold assembly clamping plates, cavity cutting-off components and side cutting-off assembly plates). The coordinated variation of the mold's male and female dies and auxiliary molding systems allows for processing a series of plastic parts with different shapes and sizes.
With the rapid development of the plastic industry and the continuous improvement in the strength of general-purpose and engineering plastics, the application scope of plastic products is expanding, and the consumption of plastic products is on the rise. A plastic mold is a tool for producing plastic products, consisting of several sets of parts that form a molding cavity within the assembly. During injection molding, the mold is clamped on an injection molding machine, molten plastic is injected into the molding cavity, where it cools and solidifies. The moving and fixed molds then separate, the product is ejected from the cavity via the ejection system, and finally the mold closes again for the next injection cycle. The entire injection molding process operates in a continuous loop.
Generally, a plastic mold is composed of two parts: the moving mold and the fixed mold. The moving mold is mounted on the movable platen of the injection molding machine, while the fixed mold is installed on the stationary platen. During injection molding, the moving and fixed molds close to form the gating system and cavity; during mold opening, they separate to facilitate the removal of the plastic product. Although the structure of molds may vary greatly depending on factors such as plastic type and properties, product shape and structure, and injection machine type, their basic structure remains consistent.
Molds are mainly composed of the gating system, temperature control system, molding parts and structural parts. Among these, the gating system and molding parts are the components in direct contact with the plastic, and they vary according to the plastic and product specifications. They are the most complex and variable parts of a plastic mold, requiring the highest machining finish and precision. The gating system refers to the runner section through which plastic flows before entering the cavity from the nozzle, including the sprue, cold slug well, runners and gates. Molding parts refer to the various components that form the product shape, including the moving mold, fixed mold, cavity, core, molding rods and exhaust ports.
Driven by high technologies and the application demands of pillar industries, China's plastic mold industry has formed a huge industrial chain. Ranging from upstream raw and auxiliary materials industries, processing and testing equipment to downstream application industries such as machinery, automotive, motorcycle, home appliance, electronic communication, and construction materials, the plastic mold industry in China is thriving with great vitality.
中文
English