The hydraulic system of injection molding machine not only depends on the rationality of system design and the performance of system components, but also because of the pollution protection 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 service life of the components. According to statistics, about 70% of the failures of the hydraulic system of the injection molding machine outside China are caused by pollution.

The harm of oil pollution to the system is mainly as follows:

1) Pollution wear of components

Various pollutants in the oil cause various forms of wear of components, solid particles into the clearance of the moving pair, the surface of the parts produce cutting wear or fatigue wear. The impact of solid particles on the surface of the components in the high-speed liquid flow causes erosion wear. The water in the oil and the products oxidized by the oil have corrosive effects on the components. In addition, the air in the oil of the system causes cavitation, resulting in surface erosion and destruction of the element.

2) Component blockage and clamping failure

Solid particles block the gap and orifice of the hydraulic valve, causing the valve core to block and clamp, affecting the working performance, and even leading to serious accidents.

3) Accelerate the deterioration of oil performance

Oil water and air with its heat energy is the main condition of oil oxidation, and the metal particles in the oil play an important catalytic role in the oxidation of oil, in addition, the water and suspended bubbles in the oil significantly reduce the strength of the oil film between the moving pairs, so that the lubrication performance is reduced.

First, the type of pollutants

Pollutants is injection molding machine hydraulic system in the oil of the system plays a harmful role in the substance, it exists in the oil in different forms, according to its physical form can be divided into: solid pollutants, liquid pollutants, gaseous pollutants.

Solid pollutants can be divided into hard pollutants, there are: diamond, cutting, silica, dust, wear metal and metal oxides; Soft pollutants include additives, water condensates, oil decomposition and polymers, and cotton silk and fibers brought in for maintenance.

Liquid pollutants are usually not in line with the requirements of the system cutting oil, water, paint and chlorine and its halides, usually we are difficult to remove, so in the selection of hydraulic oil to choose in line with the system standards of hydraulic oil, to avoid some unnecessary failures.

Gaseous pollutants are mainly mixed with the air in 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 in the various valves, the limited control, importance and accuracy of these gaps are extremely important for a reliable injection molding machine hydraulic system.

2, pollutant source

the system source of contamination in the oil ways mainly have the following several aspects:

1) external invasion of pollutants: External intrusive pollutants are mainly grit or dust in the atmosphere, usually through the tank porosity, cylinder seal shaft, pump and motor shaft intrusion into the system. The main effect is the use of the environment.

2) Internal pollutants: components in the processing, assembly, debugging, packaging, storage, transportation and installation and other links of residual pollutants, of course, these processes are unavoidable, but can be reduced to a minimum, some special components in the assembly and debugging need to be carried out in the environment of clean room or clean table.

3) Pollutants produced by the hydraulic system of the injection molding machine: System in the process of operation due to the wear and tear of the components of the particles, the sand falling off the casting, the metal particles falling off the pump, the valve and the joint, the rust in the pipeline to its oil oxidation and decomposition of the particles and glue, more serious is the system pipeline before the formal operation without washing and a large number of impurities.

Maintenance of the system

A system is generally washed before being formally put into operation, the purpose of washing is to remove the pollutants remaining in the system, metal chips, fiber compounds, iron cores, etc., in the first two hours of work, even if there is no complete damage to the system, It will also cause a series of failures. Therefore, the following steps should be followed to clean the system oil circuit:

1) Clean the tank with a cleaning solvent that is easy to dry, and then remove the solvent residue with filtered air.

2) Clean all the pipelines of the system, and in some cases, it is necessary to impregnate the pipelines and joints.

3) Install oil filter in the pipeline to protect the oil supply pipeline and pressure pipeline of the valve.

4) Install a flushing plate in the collector to replace precision valves, such as electro-hydraulic servo valves, etc.

5) Check that all lines are properly sized and properly connected.

If the electro-hydraulic servo valve is used in the system, I may wish to say two more words, the servo valve has to wash the plate to make the oil flow from the oil supply pipeline to the collector, and directly return to the tank, so that the oil can be repeatedly circulated to flush the system, so that the oil filter filters out the solid particles, the washing process, not every 1 ~ 2 hours to check the oil filter, In case the oil filter is blocked by pollutants, the bypass should not be opened at this time, if it is found that the oil filter begins to block, immediately change the oil filter.

Flushing cycle 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, then install the new oil filter, remove the washing plate, install the valve to work!

Planned maintenance:

Establish the system regular maintenance system, the injection molding machine hydraulic system better maintenance system recommendations are as follows:

1) up to 500 hours or three months to check and replace the oil filter.

2) regularly flush the imported oil filter of the oil pump.

3) Check the hydraulic oil is acidified or other pollutants pollution, the smell of hydraulic oil can roughly identify whether the deterioration.

4) Repair leaks in the system.

5) Ensure that no foreign particles enter the tank through the vent cap of the tank, the plug seat of the oil filter, the sealing gasket of the return line, and other openings of the tank.