The working principle of the zipper machine is similar to the syringe used for injection. It uses the thrust of the screw (or plunger) to inject the plasticized plastic in the molten state (that is, the viscous fluid state) into the closed mold cavity. The process of obtaining the product after the curing and shaping process inside the zipper machine.

The working principle of the injection molding of the zipper machine is a cyclic process, each cycle mainly includes: quantitative feeding-melting and plasticizing-pressure injection-filling and cooling-mold opening and drawing parts. After the plastic part is pulled out, the mold is closed again for the next cycle.　　

The operation items of zipper machinery include three aspects: keyboard operation, electrical control system operation and hydraulic system operation. Carry out the injection process action, feeding action, injection pressure, injection speed, ejection type selection, temperature monitoring of each section of the barrel, injection pressure and back pressure adjustment, etc.　　

The general forming process of screw zipper machinery is: first add granular or powdered plastic into the barrel, and make the plastic into a molten state through the rotation of the screw and the heating of the outer wall of the barrel.

Then the zipper machine closes the mold and moves the injection seat forward, so that the nozzle is close to the gate of the mold, and then pressurized oil is passed into the injection cylinder to push the screw forward, so as to melt the melt at a high pressure and a faster speed. The material is injected into a closed mold with a lower temperature.

After the zipper machine is maintained under pressure for a certain period of time and pressure (also known as pressure holding), and cooled to solidify and form, the mold can be opened to take out the product. The purpose of the zipper machine to hold the pressure is to prevent the backflow of the melt in the mold cavity. Add materials to the cavity and ensure that the product has a certain density and dimensional tolerance.

The basic requirements for the working steps of mechanical injection molding of zipper are plasticization, injection and molding. Plasticization is a prerequisite for realizing and ensuring the quality of molded products. In order to meet the requirements of molding, it is necessary to ensure sufficient pressure and speed during mechanical injection molding of the zipper.

At the same time, due to the high injection pressure of mechanical injection molding of the zipper, a correspondingly high pressure is generated in the mold cavity (the average pressure in the cavity is generally between 20 and 45 MPa), so there must be a sufficient clamping force. It can be seen that the injection device and the clamping device are the key components of the zipper mechanical injection molding process.