1. Plastic Injection Molds
This is the most widely used type of molding die in the production of thermoplastic plastic parts. The corresponding processing equipment for plastic injection molds is the plastic injection molding machine. The plastic is first heated and melted in the heated barrel of the injection machine, and then, driven by the screw or plunger of the injection machine, it enters the mold cavity through the nozzle and gating system of the mold. The plastic cools and hardens to form the product, which is then ejected from the mold. Its structure usually consists of molding parts, gating system, guiding parts, ejection mechanism, temperature control system, venting system, and support parts. The manufacturing materials usually use plastic mold steel modules, and the commonly used materials are mainly carbon structural steel, carbon tool steel, alloy tool steel, and high-speed steel. Injection molding is usually only suitable for the production of thermoplastic products. Plastic products produced by injection molding are very widespread, ranging from daily necessities to various complex mechanical, electrical, and transportation vehicle parts. It is the most widely used processing method in plastic product manufacturing.
2. Plastic Compression Molds
This includes two types of mold structures: compression molding and transfer molding. They are mainly used to mold thermosetting plastics, and the corresponding equipment is a compression molding machine. In compression molding, according to the characteristics of the plastic, the mold is heated to the molding temperature (generally 103°-108°C), and then the measured amount of molding powder is placed in the mold cavity and feeding chamber. The mold is closed, and the plastic softens and flows under high heat and high pressure. After a certain period of time, it solidifies and takes the desired shape. Transfer molding differs from compression molding in that it has a separate feeding chamber. Before molding, the mold is closed, and the plastic is preheated in the feeding chamber to a viscous state. Under pressure, it is injected into the mold cavity, where it hardens and forms the product. Compression molds are also used to mold some special thermoplastic plastics, such as difficult-to-melt thermoplastic plastics (such as polyvinylidene fluoride) blanks (cold compression molding), resin lenses with high optical properties, and slightly foamed cellulose nitrate car steering wheels. Compression molds mainly consist of a cavity, feeding chamber, guiding mechanism, ejection parts, and heating system. Compression molding is widely used in the encapsulation of electrical components. The materials used in the manufacture of compression molds are basically the same as those used for injection molds.
3. Plastic Extrusion Molds
These are a type of mold used to form continuous-shaped plastic products, also known as extrusion dies. They are widely used in the processing of pipes, rods, monofilaments, sheets, films, wire and cable coatings, and profiles. The corresponding production equipment is a plastic extruder. The principle is that solid plastic melts and plasticizes under heating and pressure from the rotating screw of the extruder, and then passes through a die of a specific shape to produce continuous plastic products with a cross-section identical to the die shape. The manufacturing materials mainly include carbon structural steel and alloy tool steel. Some extrusion molds also incorporate wear-resistant materials such as diamond in parts requiring wear resistance. Extrusion molding is usually only suitable for the production of thermoplastic products, and its structure is significantly different from injection molds and compression molds.
4. Plastic Blow Molding Molds
These are molds used to form hollow plastic containers (such as beverage bottles, daily chemical products, and various packaging containers). Blow molding methods, according to the process principle, mainly include extrusion blow molding, injection blow molding, injection stretch blow molding (commonly known as "injection-stretch-blow"), multi-layer blow molding, and sheet blow molding. The equipment corresponding to hollow product blow molding is usually called a plastic blow molding machine. Blow molding is only suitable for the production of thermoplastic products. Blow molding molds have a relatively simple structure, and the materials used are mostly carbon steel.
5. Plastic Thermoforming Molds
These are molds used to form some relatively simple plastic products using plastic sheets and films as raw materials. The principle is to use vacuum forming or compressed air forming methods to deform the plastic sheet or film fixed on the concave or convex mold under heating and softening conditions, so that it adheres to the mold cavity to obtain the desired molded product. It is mainly used in the production of some daily necessities, food, and toy packaging products. Due to the low pressure during the molding process, vacuum forming molds are often made of cast aluminum or non-metallic materials and have a relatively simple structure.
6. High-Foam Polystyrene Molding Molds
These are molds used to form various shapes of foamed plastic packaging materials from expandable polystyrene (bead-shaped material composed of polystyrene and a foaming agent). The principle is that expandable polystyrene is molded by steam in the mold. There are two types: simple manual operation molds and hydraulic press direct-injection foam plastic molds. They are mainly used to produce packaging products for industrial goods. The materials used to manufacture these molds include cast aluminum, stainless steel, and bronze.
