Plastic injection molding working process KYLT daily work Apr 6 2026

Plastic injection molding working process - KYLT daily work Apr. 6, 2026

Plastic injection molding working process

The working process of plastic injection molding is an efficient and repeatable manufacturing process used to produce a large number of complex-shaped plastic products. The core principle is to inject molten plastic into the mold cavity under high pressure, cool and solidify it, and then remove the finished product.

The entire workflow is a cyclical process, mainly consisting of the following six key stages:

1. Plastic Injection Mold Closing

The mold is closed by the clamping device of the injection molding machine to ensure the sealing of the mold cavity and prepare for injection.

2. Plastic material Injection/Filling

Plastic particles enter the heating drum from the hopper and melt and plasticize under the shear heat and external heating generated by the rotation of the screw. Subsequently, the screw advances forward and injects molten plastic into the closed mold cavity at high speed through the nozzle, filling it to about 95%.

3. Packing/Holding Pressure

After the filling is completed, the screw continues to maintain pressure, compact the melt, and compensate for the shrinkage during the plastic cooling process to prevent shrinkage marks or voids in the product. This stage continues until the gate freezes.

4. Cooling of plastic molded parts

The cooling system (usually a waterway) circulates a cooling medium in the mold to solidify and shape the plastic inside the mold cavity. Cooling time accounts for 70% to 80% of the entire molding cycle and is a key factor affecting production efficiency.

5. Mold Opening

After the product is fully cooled, the movable mold part is driven back by the mold closing device to achieve mold opening.

6. Demoulding (Ejection) 

The finished product is pushed out of the mold through ejector mechanisms such as ejector pins and top plates, completing a complete cycle.
This process is suitable for the vast majority of thermoplastic and some thermosetting plastics, and has advantages such as high production efficiency, good dimensional accuracy, and the ability to automate continuous production.

7. Quality Checking and Packing

As per the drawing's requirement to check dimensions. After checking, plastic parts can be packed in a carton box on a pallet for export.

For a free quote of all kinds of plastic injection molds and plastic molding parts manufacturing service, please contact: cnkylt@aliyun.com