Injection molding machine is a kind of equipment commonly used to manufacture plastic products. It is widely used in many industries such as automobiles, electronics, packaging, and daily products. It converts plastic raw materials into precise plastic products by high-temperature heating and high-pressure injection. The injection molding process is efficient and automated, and can produce plastic parts of various shapes, sizes, and complexity. This article will discuss in detail the main working principles of the injection molding machine and how it converts plastic raw materials into molded products.

1. Basic structure of injection molding machine
Injection molding machine mainly consists of the following core components:

Injection unit: responsible for heating, melting and injection of plastic raw materials. Including screw, heating zone, plasticizing system, etc.
Mold system: used to define the shape and size of the final product. The mold consists of two parts: fixed mold and movable mold.
Mold clamping unit: responsible for closing the two parts of the mold tightly together to ensure the sealing of the injection process.
Control system: Control the entire injection molding process through a computer or PLC system, including parameters such as temperature, pressure, and injection speed.
2. Working process of injection molding machine
The working process of the injection molding machine can be divided into several key steps, each of which involves complex mechanical and thermodynamic processes.

2.1 Preparation of plastic raw materials
First, put plastic particles (such as polyethylene, polypropylene, ABS, etc.) into the hopper of the injection molding machine. The plastic particles enter the screw through the hopper, and the screw will push the plastic particles forward by rotating.

2.2 Plasticization process
Under the push of the screw, the plastic particles are heated to the melting temperature. Usually, the screw is heated to between 200℃ and 300℃ (the specific temperature varies according to different plastic materials). At this time, the plastic particles are completely melted into a uniform molten state. During the plasticization process, the screw is not only responsible for heating and melting the plastic, but also keeps the molten plastic uniform through rotation and forward movement to prevent uneven material distribution.

2.3 Injection process
When the plastic is completely melted, the injection molding machine will start the injection process. The screw stops rotating and pushes the molten plastic into the mold at high speed through the hydraulic system. This process is usually completed within a few seconds, and the plastic is injected into the mold cavity under high pressure to fill the entire mold cavity.

The pressure during the injection process can usually reach several hundred MPa, and the injection speed is also quite high, ensuring that the plastic can quickly fill the entire mold and avoid voids or unevenness.

2.4 Holding pressure and cooling
After the plastic is injected into the mold, the injection molding machine will continue to hold the injected molten plastic, maintain a certain pressure, ensure that the plastic fills every detail of the mold, and prevent defects caused by shrinkage. During the holding pressure process, the molten plastic begins to cool and gradually solidify to form a solid plastic part.

The cooling time depends on the type of plastic material, the thickness of the mold and other factors. The cooling process is crucial, which affects the dimensional stability and surface quality of the molded product. Usually, there will be cooling water channels in the mold, and the flow of cooling water accelerates the solidification of the plastic.

2.5 Demolding and product removal
When the plastic is completely cooled and solidified, the clamping unit will separate the mold into two parts: a fixed mold and a movable mold. At this time, the molded plastic product is pushed out of the mold. This process is usually completed by a push rod or a robotic arm to ensure that the product is completely removed from the mold.

3. Key Control Factors in the Injection Molding Process
The molding effect of the injection molding machine is closely related to multiple factors, especially the following key parameters:

3.1 Injection Pressure and Injection Speed
Injection pressure and injection speed directly affect the quality of the molded product. Appropriate injection pressure can ensure that the molten plastic completely fills the mold to avoid bubbles, lack of material or voids. Too fast or too slow injection speed will lead to poor molding effect, so precise control is required.

3.2 Temperature Control
Temperature control is crucial. Too high or too low temperature will cause adverse reactions of plastic during the injection molding process. The heating system of the injection molding machine is responsible for heating the plastic to the appropriate melting temperature, while the temperature control of the mold affects the cooling rate and product quality.

3.3 Mold Design
The design of the mold determines the appearance and quality of the final product. The cooling system design, runner design and exhaust design of the mold will affect the fluidity and cooling rate of the plastic, thereby affecting the precision and surface quality of the final product.

3.4 Cycle Time
The cycle time of the injection molding process usually ranges from tens of seconds to several minutes. Too long a cycle time will affect production efficiency, while too short a cycle time may result in incomplete molding of the product. Therefore, reasonable cycle time scheduling is crucial to both production efficiency and product quality.