Material Melting:
Plastic pellets are fed into the hopper of an injection molding machine and enter the heated screw barrel through gravity or mechanical feeding. Inside the barrel, the plastic pellets are heated by the heater and gradually melt into a viscous molten state under the rotation and shearing action of the screw.
Screw Metering:
As the screw rotates, it pushes the molten plastic forward and stores it at the metering position at the front end of the screw. During this process, the screw slightly retracts under pressure to control the accuracy of the injection volume.
Injection:
Once the molten plastic reaches the predetermined amount and the mold is closed, the screw rapidly advances, injecting the molten plastic through the nozzle into the mold cavity. Injection speed and pressure are critical parameters that affect the molding quality and surface finish of the chopsticks.
Packing and Cooling:
After the mold is filled with plastic, the screw maintains a certain pressure for a period of time to compensate for the volume change caused by plastic shrinkage during cooling. Subsequently, the plastic inside the mold starts to cool and solidify.
Cooling:
The duration of this cooling phase depends on the type of plastic, the thickness of the chopsticks, and the cooling performance of the mold. During cooling, the mold remains closed to ensure the shape integrity and dimensional stability of the chopsticks.
Ejection:
Once the cooling is complete, the mold opens, and the chopsticks are ejected from the mold using ejector pins or other ejection mechanisms. If the mold is well-designed and operated correctly, the chopsticks should easily eject without significant deformation or residual flash.
The entire injection molding process requires precise control of temperature, pressure, speed, and time to ensure high quality and consistency of the chopsticks. Proper adjustment and monitoring of these parameters are crucial, especially in large-scale production.