How Does The Injection Molding Machine Work?

The working principle of the injection molding 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 curing and shaping. Injection molding is a cyclic process, and each cycle mainly includes: quantitative feeding-melting and plasticizing-pressure injection-mold filling and cooling-mold opening and picking. After taking out the plastic part, the mold is closed again for the next cycle.

An injection molding machine has two basic components: an injection device and a mold clamping device for melting and feeding plastic into the mold.

The function of the clamping device is:

1. Make the mold close under the condition of withstand the injection pressure;

2. Take the product out of the injection device to melt the plastic before it is injected into the mold, and then control the pressure and speed to inject the melt into the mold. The injection device used today has two designs: screw preplasticizer or two-stage device, and reciprocating screw. The screw pre-plasticizer uses a pre-plasticizing screw (first stage) and then injects molten plastic into the injection rod (second stage).

The advantages of the screw preplasticizer are constant melt quality, high pressure and high speed, and precise injection volume control (using mechanical thrust devices at both ends of the piston stroke). These advantages are required for transparency, thin-walled products and high production rates. Its disadvantages include uneven residence time (causing material degradation), higher equipment costs and maintenance costs.

The most commonly used reciprocating screw injection device does not require a plunger to melt and inject the plastic.

The basic functions of the injection molding machine

(1) Heat the plastic to reach a molten state;

(2) Apply high pressure to the molten plastic to make it eject and fill the mold cavity.

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