Dongguan Jieyang Machinery Co., LtdDongguan Jieyang Machinery Co., Ltd


Hydraulic System of Injection Molding Machine

181 Published by Sabrina wang Aug 05,2020

Hydraulic System of Injection Molding Machine

hydraulic system of injection molding machine

The quality of the hydraulic system of the injection molding machine not only depends on the rationality of the system design and the performance of the system components, but also due to the pollution prevention and treatment of the system, the pollution of the system directly affects the reliability of the hydraulic system of the injection molding machine and the use of components life.

According to statistics, about 70% of hydraulic system failures of injection molding machines at home and abroad are caused by pollution. The main hazards of oil pollution to the system are as follows:

1. Contamination and wear of components

Various pollutants in the oil cause various forms of wear of the components, and solid particles enter the gap of the moving pair, causing cutting or fatigue wear on the surface of the part. The impact of solid particles in the high-speed liquid flow on the surface of the component causes erosion and wear.

The water in the oil and the oxidation and deterioration products of the oil have a corrosive effect on the components. In addition, the air in the oil of the system causes cavitation, which leads to erosion and damage to the surface of the components.

2. Component blockage and clamping failure

Solid particles block the gaps and orifices of the hydraulic valve, causing blockage and clamping of the valve core, affecting the working performance, and even causing serious accidents.

3. Accelerate the deterioration of oil performance

The water and air in the oil are the main conditions for oil oxidation due to their thermal energy. The metal particles in the oil play an important role in the oxidation of the oil. In addition, the water and suspended bubbles in the oil significantly reduce the movement. The strength of the oil film reduces the lubrication performance.


Pollutants are substances that are harmful to the oil in hydraulic system of the injection molding machine . They exist in different forms in the oil. According to their physical forms, they can be divided into solid pollutants, liquid pollutants, and gaseous pollutants.

Solid pollutants can be divided into hard pollutants, including: diamond, cutting, silica sand, dust, wear metals and metal oxides; soft pollutants: additives, water condensate, oil decomposition products and polymers, and maintenance Cotton silk and fiber brought in at the time.

Liquid contaminants are usually grooving oil, water, paint, chlorine and its halides that do not meet the system requirements, which are usually difficult to remove. Therefore, when selecting hydraulic oil, choose hydraulic oil that meets the system standards to avoid unnecessary failure.

Gaseous pollutants are mainly air mixed into the system:

These particles are often so small that they cannot settle down and are suspended in the oil, and are finally squeezed into the gaps of various valves. For a reliable hydraulic system of injection molding machine , these gaps have a limited effect. Control, importance and accuracy are extremely important.


The main sources of pollutants in the system oil are as follows:

1. Externally invading pollutants: The externally invading pollutants are mainly sand or dust in the atmosphere, usually invading the system through the air holes of the fuel tank, the sealing shaft of the oil cylinder, pumps and motors. Mainly the impact of the use environment.

2. Internal contaminants: contaminants remaining in the components during processing, assembly, commissioning, packaging, storage, transportation and installation. Of course, these processes cannot be avoided, but they can be minimized. Some special components are in the assembly and The debugging needs to be carried out in a clean room or clean bench environment.

3. Pollutants generated by the hydraulic system of the injection molding machine: particles produced by the wear of components during the operation of the system, sand particles falling off from castings, metal particles falling off from pumps, valves and joints, and corrosion and spalling in the pipeline. The particles and jelly produced by the oxidation and decomposition of the oil are more serious because the system pipeline has not been flushed before the formal operation.


A system is generally flushed before it is officially put into use. The purpose of flushing is to remove the contaminants, metal shavings, fiber compounds, iron cores, etc. remaining in the system. In the first two hours of work, even if the system is not completely damaged, it will Cause a series of failures.

Therefore, the system oil circuit should be cleaned according to the following steps:

  • Clean the fuel tank with an easy-to-dry cleaning solvent, and then use filtered air to remove solvent residues.
  • Clean all pipes of the system. In some cases, it is necessary to immerse the pipes and joints.
  • Install oil filter in the pipeline to protect the oil supply pipeline and pressure pipeline of the valve.
  • Install a flushing plate on the collector to replace precision valves, such as electro-hydraulic servo valves.
  • Check whether all pipes are of proper size and connected correctly

If an electro-hydraulic servo valve is used in the system, the flushing plate of the servo valve should enable the oil to flow from the oil supply line to the collector and return directly to the oil tank, so that the oil can circulate repeatedly to flush the system and filter the oil. Filter out the solid particles. During the flushing process, check the oil filter every 1 to 2 hours to prevent the oil filter from being blocked by contaminants. Do not open the bypass at this time. If the oil filter starts to be blocked, immediately change the oil filter.

The cycle of flushing is determined by the structure of the system and the degree of system pollution. If the sample of the filter medium has no or few foreign pollutants, install a new oil filter, remove the flushing plate, and install the valve to work!

Planned maintenance, establish a regular maintenance system for the system, and recommend a better maintenance system for the hydraulic system of the injection molding machine as follows:

  • The oil filter should be inspected and replaced at most 500 hours or three months.
  • Flush the imported oil filter of the oil pump regularly.
  • Check whether the hydraulic oil is contaminated by acidification or other contaminants. The smell of the hydraulic oil can roughly identify whether it has deteriorated.
  • Repair the leak in the system.
  • Make sure that no foreign particles enter the fuel tank from the vent cap of the fuel tank, the plug seat of the oil filter, the sealing gasket of the oil return line and other openings of the fuel tank.