What is plastic injection molding? The principle and steps of plastic injection molding

What is plastic injection molding? The principle and steps of plastic injection molding
Today I want to share with you what is plastic injection? What is the relation between plastic injection and us? In fact, plastic products are very common in everyone's lives, such as the 3C products we use every day, "mobile phones, computer cases," and "computer keyboards"; daily household items "fresh-keeping boxes" and "portable water bottles"; even large enough to "automobile shell panels", "furniture", etc., will use plastics. The wide application of plastic materials is closely related to our lives. What are key points that we should pay attention in plastic injection molding, and what are the injection processes about the products we see in the market? Let us check it together!

What is the concept of plastic injection?

Plastic injection technology is mainly used to manufacture various plastic products that we see in our lives. The principle of injection molding is to first heat and melt granular plastic pellets into a liquid and flowable state through an injection molding machine at a high temperature. The molten plastic material is injected into the mold, and after a period of time is cooled down, the final plastic product is completed after the mold is opened. Plastic injection products are very diversified, because injection molding steel molds can be produced according to product requirements with different complexity, precision, and styles. However, relatively the cost of mold opening is high, which also affects the cost of plastic injection molding. There are many factors. We have helped you sort out the cost of plastic products before. Does the company need to buy an injection molding machine? If you are also troubled by this, let's take a look at the cost of injection molding first!

〈Extended reading : What are injection molding machines? What are the types?

〈Extended reading: An article to understand the cost of plastic injection products? Is it cost-effective to buy an injection molding machine? A must-see for company purchasing!

Plastic injection molding process

We simplified the plastic injection molding process into 5 steps, plasticizing ⇒ injection ⇒ holding pressure ⇒ cooling ⇒ demolding. These 5 stages will continue to circulate during the manufacturing process. With the trend of automated production, it can be efficiently mass-production to supply the required plastic products.

1. plasticizing

The plastic material is melted at high temperature in the material tube, and the plastic processing temperature is set on the injection molding machine according to the characteristics of the selected plastic material, so that the plastic pellets are dissolved at the correct temperature.

2. injection

The plastic material is filled and injected into the mold through the screw, and the mold design space is used to shape the plastic. At this time, the parameters of the injection machine must be adjusted according to the plastic injection molding conditions or mold conditions to avoid subsequent problems such as size incompatibility and burrs.

3. holding pressure

After the plastic materials are filled into the mold, continue to pressurize the space in the mold, mainly to ensure the tightness of the filling of these plastic materials, and to avoid the backflow of the materials.

4. cooling

The product is quickly cooled and shaped in the mold.

5. demolding

Finally, the plastic product is completed, and the product is removed from the mold.

〈Extended reading :  How to choose the injection machine? 8 key points let you find the right injection molding machine!

3 key points of plastic injection molding

Key 1: Dryness of plastic materials

Plastic raw material is usually in a solid or elastomeric state at normal room temperature. During plastic injection process, the raw material is heated to turn the solid plastic raw material into a fluid and moldable molten liquid for subsequent injection. During the plastic injection process, it should pay attention to the dryness of the plastic raw materials. If the raw material with moisture is put into the high-temperature barrel, the plastic injection process is likely to be unstable and even affect the product apperance and quality after injection molding. Common raw material in the industry include PP, PA, PE, PC, ABS, etc. In fact, some plastic raw material contains a small part of moisture on the surface, such as PA and PC, which needs to be dried separately. So before the production starts, it is necessary to confirm which kind of plastic raw material is used? And ensure the dryness of the plastic raw materials before proceeding with the injection procedure.

Key point 2: Injection molding machine selection

There are many types of plastic injection machines in the market, and the choice of model is a key to plastic injection, because the size, weight, and plastic materials of the product you want to build are different, and the suitable injection machine will also be different. In addition to consider the properties of plastic injection products, we recommend that you also consider the mold opening stroke, clamping force, injection shoot, screw compression ratio, injection speed, etc. to select the injection model that is most suitable for your product.

Key point 3: Adjustment of plastic injection parameters

Personnel operation skills are very important in the plastic injection molding process. The so-called operation technology is actually to control the injection parameter settings and make adjustments at any time. We divide the adjustment range of plastic injection parameters into 5 categories: "temperature", "pressure", "speed","position", and "Time". The temperature setting is quite important. It needs to be used to adjust the drying temperature of the plastic material, the heating temperature of the injection machine barrel, and the mold cooling temperature. Other parameter settings are based on the plastic injection steps and for each product's injection status, detailed adjustments are made at the right time. The earliest masters used their feelings or experience to adjust the machine. However, with the development of technology, the current injection molding machines can be adjusted the parameters in time through the instant data feedback.


Plastic injection is a process that can quickly produce plastic products. There are many points to consider and pay attention to in the process of plastic injection molding. From the selection of injection models, plastic material selection to mold making, all of them need to detaily review and evaluation. We are one of the few brands in Taiwan that produce its own injection machines. It can help you find the most suitable injection machine for your product. Of course, in addition to choosing the injection model at the beginning, it is also important to have the product designers and experienced technical operations during the plastic injection process. All the conditions work together to create the perfect plastic product.
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