What Stages Do Injection Molding Require

Plastic molds are ultimately used in the production of plastic products, with injection molding being a common process. The main processes include: mold closing, injection molding, pressure holding (pre molding), cooling and shaping, mold opening, ejection, and mold closing. There is a cyclic process during the injection process, which involves three stages: pre molding, injection, and cooling and shaping. The mold manufacturer will provide detailed instructions on the specific process for each stage.
The first stage is the pre molding stage. The spiral begins to rotate, and then the plastic from the hopper is transported to the front end of the spiral. Under the action of high temperature and shear force, the plastic is uniformly plasticized at the front end of the spiral and gradually gathers to the front end of the spiral. As the molten plastic gathers, the pressure increases. Finally, the back pressure at the rear end of the spiral is overcome, and the spiral is gradually pushed back. When the plastic at the front end of the spiral reaches the required injection amount, the retreat and rotation stop, and the pre molding stage ends.
Next is the injection molding stage. Under the action of the injection cylinder, the screw moves forward, pushing the plastic stored in front of the barrel forward at multiple speeds and pressures, and injecting it into the closed mold cavity through the flow channel and gate.
The third stage is the cooling and solidification stage. Maintain pressure on the plastic inside the mold cavity to prevent it from flowing back until it solidifies and the pressure inside the mold cavity disappears. The cooling and setting time accounts for the largest proportion in a production cycle.