Definition of plastic (American Plastics Industry Association):
Plastics are mainly composed of carbon, oxygen, hydrogen, nitrogen, and other organic or inorganic elements. Finished product is a solid. It is a molten liquid during manufacturing process. Therefore, it can be heated to melt, pressurized to flow, and cooled to solidify to form various shapes. This large and varied material group is called plastic.
Plastic parts (abbreviated as plastic parts, same below) are widely used in every field of modern life, such as household appliances, instruments, wires and cables, construction equipment, communications electronics, automotive industry, aerospace, daily hardware, etc.
In recent years, with rapid development of plastic industry and continuous improvement of plastic performance, plastic parts have been widely used. Plastic parts are replacing traditional metal parts in different fields. A reasonably designed plastic part can often replace multiple traditional metal parts, so as to simplify product structure and save manufacturing costs.

 

There are many processing methods for plastic parts, including injection molding, extrusion molding, calender molding, blow molding, suction molding, and compression molding.
There are various processing methods for high molecular polymers such as plastics. Each method has its advantages and disadvantages and is more suitable for specific applications.
Next, let's see how they are processed through relevant animated pictures!

 

 

Injection molding is a manufacturing method that manufactures parts by injecting materials into molds. Main method of processing plastic is injection molding. In this process, plastic is placed in hopper, then hopper heats and injects plastic, which is pushed through a long chamber and a reciprocating screw. After that, it is softened into a fluid state. Nozzle is located at the end of chamber, and fluid plastic is forced to cool through nozzle, closing mold. When plastic cools and solidifies, semi-finished product exits press.
Animation is an injection molding process. Principle is very similar to that of a hospital syringe (so sometimes injection molding is also called injection). Plastic particles are melted in injection molding machine, extruded into mold, and cooled to obtain product.

 

 

 

 

Plastic extrusion is a mass manufacturing method in which plastic raw materials are melted to form a continuous contour. Extrusion process is usually used to make films, continuous sheets, tubes, profiles, rods, outer wires, filaments, threads, and cables. Together with injection molding machine, dried plastic is placed in a hopper and sent into a long heating chamber. At the end of cavity, material is pressed out of a small opening, or mold in the shape of desired final product. After plastic leaves mold, it is placed on a conveyor belt to cool. A blower is sometimes used in this process to help it cool down.
Similarly, although most of raw materials used in extrusion process are rubber, there are also cases of plastic extrusion, such as TPV.

 

 

Blow molding is a molding method for manufacturing hollow plastic products. It is a secondary molding technology that uses gas pressure to inflate rubber-like parison closed in mold cavity into a hollow product.

 

 

A special plastic processing method for processing thermoplastic plastic sheets into various products. Sheet material is clamped on frame and heated to a softened state, under action of external force, it is made to close to molding surface of mold to obtain a shape similar to molding surface. After cooling and shaping, finished product is finished. This process is also used in rubber processing. In recent years, thermoforming has made new progress, such as continuous production technology from extruding sheet to thermoforming.
Second animation shows two-piece thermoforming process.

 

 

Compression molding is the most commonly used method for thermoset materials and is not usually used for thermoplastics. During this process, material is extruded into desired shape. Plastic molding powder and other materials are added to mixture to produce special qualities. When mold is closed and heated, material hardens to form its desired shape. Temperature, pressure and length of time used in process depend on desired result.

 

 

Last process of heavy leather finishing. Use plasticity of fiber under mixed heat conditions to flatten surface of fabric or roll out parallel fine diagonal lines to enhance finishing process of fabric gloss.

 

 

What is calendering: Process of extruding and stretching material into a plastic film and sheet with a certain specification and shape through a special calendering equipment.

 

Plastics are also calendered. After plastic material is fed, it is heated and melted, then formed into a sheet or film, then cooled and rolled up. The most commonly used calendering material is polyvinyl chloride PVC.

 

Pultrusion molding is a processing method of blank material. Processing process is that blank is extruded from orifice or gap of die under action of three-way uneven compressive stress, so that cross-sectional area is reduced and length is increased to become desired product. .

 

 

Vacuum forming is often called blister. It is a kind of plastic processing technology. Main principle is to heat and soften flat plastic hard sheet, then use vacuum to absorb it on the surface of mold and cool it to form. It is widely used in plastic packaging, lighting, advertising, decoration and other industries.

 

 

Rotational molding process is to first add plastic raw materials into mold, then mold is continuously rotated along two vertical axes and heated, so that plastic raw materials in mold gradually uniformly coat and melt adhere to mold cavity under action of gravity and thermal energy, formed into required shape, then cooled, shaped and demolded. Finally, product is obtained.

 

Dripping is use of plastics with variable state characteristics, that is, it has viscous fluidity under certain conditions, and can restore to solid state at room temperature. It is universally used with certain tools, and it is molded into designed shape according to requirements in its viscous flow state, then solidified and molded at room temperature.
Dripping craftsmanship is widely used in decoration of various trademark nameplates, cards, daily-use hardware products, travel commemorative badges, exquisite handicrafts and cover of advanced books.

 

Resin Transfer Moulding (RTM) is a composite material production process in which a reinforcing agent is placed in a mold to form a certain shape, then resin is injected into mold, impregnated with fibers, and cured.
This technology eliminates need for prepregs and autoclaves, effectively reducing equipment costs and molding costs. It is widely used in aircraft industry, automobile industry, shipbuilding industry and other fields.

 

Foam molding is process of adding appropriate foaming agents to foam materials (PVC, PE, PS, etc.) to make plastic produce a microporous structure. Almost all thermosetting and thermoplastic plastics can be made into foam plastics, foam molding has become an important field in plastic processing.