Thermoplastics become soft and active when heated and harden when cooled to form products. This process is reversible and can be repeated. Polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyformaldehyde, polycarbonate, polyamide, acrylic plastics, other polyolefins and their copolymers, polysulfone, polyphenyl ether, chlorinated polyether and so on are thermoplastic plastics. Resin molecular chains in thermoplastics are linear or branched structures. There are no chemical bonds between molecular chains. Softening activities occur when heated, and the process of cooling and hardening is a physical change.

Thermoplastic injection moulding is to melt the plastic material and then inject it into the film cavity. Once molten plastic enters the mould, it is cooled to form a relative shape according to the cavity pattern. The resulting shape is often the final product, and no other processing is required before the automatic moulding machine equipment or as a product is used. Many details, such as protrusions. Ribs and threads can be formed in one step operation of injection moulding. The injection moulding machine has two base parts: the injection equipment and the clamping equipment for melting and feeding plastic to the moulds.

The function of clamping equipment lies in:

1. Close the die under the pressure of injection.

2. Remove the product. The injection equipment melts the plastic before it is injected into the mould, and then controls the pressure and speed to inject the melt into the mould. There are two kinds of plans for the injection equipment: screw pre-plasticizer or two-stage equipment, and reciprocating screw. The screw pre-plasticizer uses the pre-plasticized screw (the first level) and then feeds the molten plastic to the injection rod (the second level).

The benefits of screw pre-plasticizer are stable melt quality, high pressure and speed, and accurate injection control (using mechanical thrust equipment at both ends of piston stroke). These benefits are needed for transparency, thin-walled products and high production rates. Its defects include uneven residence time (leading to material degradation), higher equipment costs and repair costs. More commonly used reciprocating screw injection equipment does not need plunger to melt plastic and injection.

The powder or granular plastic in the hopper is melted, and the rolled screw is sent to the front end of the screw, where the plastic fluid flows through the front end of the screw and accumulates in front of the screw. The stacking of molten plastics in front of the screw pushes the screw to the back of the injection equipment. The roll of the screw, the stacking of molten materials and the movement to the back continue to constitute the relative injection volume. During the working cycle of our equipment, the screw tip is closed to prevent material from coming back along the screw. The function of screw tip and feed screw is like that of feeding plunger, pressing plastic into die.

The benefits of reciprocating screw include reduced plastic residence time, self-cleaning screw and screw tip. These benefits are critical when screw and barrel are to be cleaned up in the processing of thermosensitive materials and in the selection of coloured materials or resin varieties.

Now the widely used clamping equipment planning includes elbow bar clamping equipment, hydraulic clamping equipment and hydraulic-mechanical clamping equipment. Elbow rod clamping equipment is suitable for small tonnage equipment because of its low cost in production planning. Its features include high mechanical benefit of locking operation, built-in clamping device, slow die damage and fast clamping operation.