Maintenance of Injection Molding Machine

Injection molding machines are generally operated 24 hours a day (shift system), and generally do not shut down. For machines that are in working condition for a long time, we must carefully do the maintenance and work hard to find and solve problems before the machine breaks down. Otherwise, once the machine breaks down, production must be stopped and machine need to be repaired, which will seriously affect production and delay delivery. Therefore, it is particularly important to do a good job in the maintenance of the injection molding machine.

Preparation for the maintenance of injection molding machine

1. Classified according to the frequency of machine problem

List the most frequent content in the daily maintenance, the less frequent in the weekly maintenance, and so on. And then classify the monthly maintenance and the annual maintenance.

2. A dedicated person is responsible for registration on time

Ensure that the maintenance work is carried out effectively according to the established plan. The necessary records must be done every time the maintenance work is completed. So that the evaluation of the machine can be based on future work.

Maintenance of the hydraulic injection molding machine

1. Maintenance of electrical system

  • When replacing the mold, preventcooling water from flowing into the machine bed electrical box.
  • Check whether the temperature in the electrical box is too high and whether it will affect the electronic main board.
  • When changing the relay,use the specified voltage relay.
  • When checking the high-voltage components in the machine,don’t turn on the main power supply unless necessary.

2. Maintenance of hydraulic system

The hydraulic oil temperature of the injection molding machine should be kept between 30°C-50°C. If the hydraulic oil temperature exceeds 60°C, it will deteriorate due to oxidation.

When the oil temperature exceeds 60°C, every 8°C increase will reduce the oil life by half. The life of oil at 90°C is only 10% of that at 60°C.

When the oil temperature rises faster, the oil’s oxidative deterioration speeds up, and the oil’s color turns black. When the acid liquid accumulated by this oxide reaches a certain level, it will bring fatal damage to the system.

When the ambient temperature is high (40°C), we should turn on the oil cooling system when turning on the machine. And that is to avoid excessive temperature rise of the system, thereby reducing the damage to the hydraulic oil.

If the oil decreasing the viscosity, it will cause damage to the oil pump, oil leakage and pressure drop. What’s more, it will affect the working efficiency of the pressure relief oil switch and reduce the duration of the oil seal.

Prevent the cooling water leaking into the oil cylinder, pay special attention to checking whether there is water leakage inside the hydraulic oil cooler. Remove the oil cooler and clean the inside every 6 months.

The hydraulic oil must be changed every 3000-4000 working hours. When changing the oil, do not mix the new and old one together. At the same time, the oil filter in the oil tank should be removed for cleaning as well.

The valve is blocked by foreign objects and fails. The valve core should be cleaned with diesel or kerosene (or immersed in clean pressure oil for cleaning). And then use the compressed air to remove the foreign objects. Unless it is sure that some foreign objects block the oil valve and causes the injection molding machine to malfunction, do not remove the oil valve casually.

3. Maintenance of the clamping unit

  • The toggle of the clamping unit has a long working life, but each movable part should be properly lubricated. Otherwise the machine toggle will reduce its life due to wear.
  • Keep the four columns clean.
  • Keep the sliding feet and sliding rails of the moving platen clean and lubricated.
  • Avoid using limit or exceeding the working pressure for clamping.
  • When adjusting the mold, the express-clamping speed is not allowed.
  • Control the position of the clamping movement stroke at the appropriate position to reduce the impact on the machine on each clamping.

4. Maintenance of the injection unit

  • Keep the guide rod of the injection unit lubricated and clean.
  • Keep the surface of the injection unit clean and dry.
  • Except for plastics resin, master bath and additives, do not put anything in the hopper. If you use the recycle material, you must add a magnetic stand in the hopper to prevent metal fragments from entering the barrel.
  • When the barrel has not reached the setting temperature, do not start the screw hydraulic motor.
  • Before using special plastics resin, you should consult the plastics manufacturer, which type of plastic injection screw is more suitable.
  • Correctly use the methods of replacing plastics resin and cleaning the barrel provided by the plastics manufacturer.
  • Periodically inspect each part of the injection unit andtighten the loose parts. Ensure that the two injection cylinders are installed even. And that is to avoid damage to the oil seal of the injection cylinder, causing oil leakage and damage to the cylinder.
  • Regularly remove the grease from the hydraulic motor part and replace it with new grease.
  • When the melting temperature is normal but the black spots or discoloration continue to appear, check whether the check ring of the screw is damaged.


Doing a good job in the maintenance of the injection molding machine can effectively extend the service life of the injection molding machine. What’s more, it can create greater economic value for the factory. Therefore, regular maintenance is essential.

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