Introduction to injection molding processing methods for thermoplastics

Update:29-12-2018
Summary:

Thermoplastic injection molding is the process of melti […]

Thermoplastic injection molding is the process of melting a plastic material and then injecting it into the membrane cavity. Once the molten plastic enters the mold, it is shaped into a shape by the cold cavity. The resulting shape is often the final product and no further processing is required prior to installation or use as a final product. Many details, such as bosses, ribs, threads, can be formed in one injection molding operation. Injection molding machines have two basic components: an injection device and a clamping device for melting and feeding plastic into the mold. The function of the mold device is to close the mold under the pressure of the injection pressure; take the product out of the injection device and melt it before the plastic is injected into the mold, and then control the pressure and speed to inject the melt into the mold after {HotTag}. There are two types of injection devices currently in use: a screw pre-plasticizer or a two-stage device, and a reciprocating screw. The screw pre-plasticizer uses a pre-plasticized screw (first stage) to inject molten plastic into the injection rod (second stage).

The advantages of the screw pre-plasticizer are constant melt mass, high pressure and high speed, and precise injection volume control (using mechanical thrust devices at both ends of the piston stroke). These strengths are required for transparent, thin-walled products and high production rates. Disadvantages include uneven residence time (resulting in material degradation), higher equipment costs, and maintenance costs.

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