The working principle of a zipper mechanism is similar to that of a syringe used for injection. It uses the thrust of a screw (or plunger) to inject the melted plastic (i.e. viscous flow state) into a closed mold cavity, and through the internal solidification and shaping process of the zipper mechanism, the product is obtained.

The injection molding working principle of zipper machinery is a cyclic process, each cycle mainly includes: quantitative feeding - melting plasticization - pressure injection - mold filling cooling - mold opening and pulling. Pull out the plastic part and then close the mold for the next cycle.

The operation items of zipper machinery include three aspects: keyboard operation, electrical control system operation, and hydraulic system operation. Select the injection process action, feeding action, injection pressure, injection speed, and ejection type separately, monitor the temperature of each section of the material barrel, and adjust the injection pressure and back pressure.

The forming process of a general screw type zipper machine is: first, granular or powdered plastic is added to the barrel, and the plastic is melted through the rotation of the screw and the heating of the outer wall of the barrel.

Then, the zipper mechanism closes the mold and moves the injection seat forward to make the nozzle close to the gate of the mold. Then, pressure oil is injected into the injection cylinder to push the screw forward, injecting the molten material into the closed mold at a lower temperature with high pressure and fast speed.