Use of injection molding machine and key points of operation

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Injection molding is a widely used manufacturing process for producing plastic parts with high precision and complex geometries. An injection molding machine plays a central role in this process, as it is responsible for melting the plastic material, injecting it into a mold, and then cooling and solidifying it to create the final product. Let's explore the use of an injection molding machine and its key points of operation:

Use of Injection Molding Machine

  1. Preparing the Mold: Before starting the injection molding process, the mold needs to be prepared. The mold consists of two halves, the cavity, and the core. It is mounted onto the injection molding machine, and the two halves are securely closed.
  2. Melting the Plastic Material: The plastic material, typically in the form of pellets or granules, is fed into the injection molding machine's hopper. Inside the machine, a heating barrel and a reciprocating screw are used to melt and mix the plastic. The plastic is heated to its melting point, becoming a molten liquid.
  3. Injection: Once the plastic is melted, the injection process begins. The screw rotates to create a measured amount of molten plastic, which is then injected into the closed mold cavity under high pressure. The pressure ensures that the molten plastic completely fills the mold and takes the shape of the mold cavity and core.
  4. Cooling and Solidifying: After injection, the mold is kept closed while the plastic inside cools and solidifies. Cooling time varies depending on the material and part thickness. Cooling can be accelerated by using cooling channels within the mold.
  5. Ejection: Once the plastic has solidified and cooled sufficiently, the mold is opened, and the part is ejected from the mold cavity using ejector pins or plates.
  6. Trimming and Finishing: In some cases, the part may require trimming or additional finishing processes to remove any excess material or to achieve the desired surface finish.
  7. Cycle Time: The entire injection molding process, including injection, cooling, and ejection, constitutes one cycle. Cycle time is the time taken for one complete cycle and is an essential factor in determining the production efficiency of the machine.

Classification and Use

The injection molding machine has the ability to form the plastic products with complex appearance, precise size or dense texture with metal inserts at a time. It is widely used in various fields of national defense, mechanical and electrical, automobile, transportation, building materials, packaging, agriculture, culture, education and health and People's Daily life. With the rapid development of plastic industry, injection molding machine plays an important role in both quantity and variety. Its total production accounts for 20%-30% of the whole plastic molding equipment, thus becoming one of the fastest growing and most productive machines in plastic machinery.

According to relevant data statistics, from 1996 to 1998, China exported 8383 sets of injection molding machines (sets) and imported 42959 sets of injection molding machines (sets). In 1998, China's injection molding machine output reached 20000 sets, and its sales accounted for 42.9% of the total sales of plastic machines.

China production injection molding machine manufacturers more, according to incomplete statistics has more than 2000. The structure of injection molding machine has two kinds: vertical and horizontal. According to the products produced can be divided into ordinary type and precision injection molding machine.

Key Points of Operation Injection Molding Machine

  1. Injection Pressure and Speed: The injection pressure and speed must be carefully controlled to ensure that the molten plastic fills the mold uniformly and without any defects. Too high a pressure or speed can cause overpacking, flash, or other molding issues.
  2. Temperature Control: Precise temperature control is crucial to achieve the optimal melt temperature and to prevent overheating or underheating of the plastic material.
  3. Mold Design: A well-designed mold is essential for producing high-quality parts. The mold should have proper gating, venting, and cooling systems to ensure a successful injection molding process.
  4. Material Selection: The choice of plastic material depends on the desired properties of the final part. It is essential to select the right material for the application to achieve the required mechanical, thermal, and chemical properties.
  5. Quality Control: Regular quality checks should be performed to ensure that the produced parts meet the required specifications. Visual inspection, dimensional measurement, and material testing are common quality control measures.
  6. Safety: Injection molding machines involve high temperatures and pressures, making safety protocols crucial. Operators should be well-trained in machine operation and safety procedures to avoid accidents and ensure a safe working environment.

Boot before

1.Before operation of injection molding machine, check whether there is water and oil in the electric control box. If the electric machine is damp, do not turn on. There should be maintenance personnel to blow dry the electrical parts before starting.

2.Before operation of injection molding machine, check whether the power supply voltage is consistent, generally should not exceed ±6%.

3.Check whether the emergency stop switch and the front and rear safety door switches are normal. Verify whether the motor and oil pump rotate in the same direction.

4.Check whether the cooling pipeline is smooth over a long distance, and pass cooling water into the cooling water jacket at the end of the oil cooler and barrel.

5.Before operation of injection molding machine, check whether there is lubricating oil in each moving part, and add enough lubricating oil.

6.Turn on the electric heating to heat each section of the barrel. When the temperature of each section reaches the requirement, hold it for another period of time to make the machine temperature tend to be stable. The holding time varies according to the requirements of different equipment and plastic raw materials.

7.Fill the hopper with enough plastic. According to the requirements of different plastics for injection molding, some raw materials are best dried first.

8.The heat shield on the barrel should be covered well to save power and extend the life of the heating ring and current contactor

The operation process

1.Do not be covet convenient, cancel the function of safety door at will.

2.Pay attention to the temperature of the pressure oil, oil temperature should not exceed the prescribed range. The ideal working temperature of hydraulic oil should be kept between 45-50℃, generally in the range of 35-60℃ is more appropriate.

3.Pay attention to adjust the travel switch to avoid the impact of the machine during operation.

End of the work

1.After the operation of the injection molding machine, the plastic in the cylinder should be cleaned up to prevent the oxidation of leftover materials or long-term heat decomposition.

2.The mould should be opened so that the toggle mechanism is locked for a long time.

3.The workshop must be equipped with lifting equipment. Great care should be taken when assembling and disassembling moulds to ensure production safety.


Injection molding machines are essential in the plastic manufacturing industry, enabling the mass production of plastic parts with high precision and repeatability. Proper operation and control of the injection molding machine are critical to producing high-quality parts efficiently. By understanding the use and key points of operation, manufacturers can optimize the injection molding process and achieve consistent and reliable results in plastic part production.