Common faults in the hydraulic system of machine tools

1. The working pressure imbalance of the machine tool hydraulic system
The working pressure imbalance of the hydraulic system is manifested as unstable pressure, delayed pressure conversion, and high unloading pressure. The cause of such malfunctions is caused by hydraulic pumps and valves. The phenomenon of trapped oil in hydraulic pumps has not been properly resolved. The pump parts are damaged or poorly processed. In response to the above reasons, elimination methods should be adopted, such as redesigning the structure for removing trapped oil and improving machining accuracy.

2. Vibration and noise
There are two main reasons for vibration and noise in the hydraulic system of machine tools. The first issue is that the machining accuracy of hydraulic pumps and motors is not high, with large flow and pressure fluctuations, severe oil trapping, and poor bearing quality, which can all cause noise. The second issue is that air enters the hydraulic system, causing cavitation. The sudden change in air volume caused by the conversion of high and low pressure during the transmission process leads to the emission of noise. For example, if the channel of the directional valve is too small or suddenly changes, high flow velocity will generate vortices; When the flow rate is high and the back pressure is high, a local vacuum is formed, causing cavitation and producing noise. After identifying the cause, corresponding measures can be taken to eliminate the fault.

3. Slow crawling
Crawling is a common fault in the hydraulic transmission system of machine tools. It not only damages the stability and precise positioning of the hydraulic system, but also has an impact on the surface quality of the machined parts. Reducing the practical life of machine tools requires timely diagnosis and troubleshooting. The reason for crawling is poor lubrication conditions; Air entering the system; Mechanical rigidity is too low, the device is improper, or the parts are deformed, worn, and the size exceeds the tolerance. If the sealing of the piston and piston rod of the hydraulic cylinder is too tight or too loose; The non concentricity of the piston and piston rod can cause uneven frictional resistance and result in crawling. The methods to eliminate crawling include: first, ensuring that the hydraulic system has sufficient rigidity. The second is to maintain sufficient lubrication and minimize the impact of friction. The third method is to use guide rail oil, by adding 0.3% -0.5% stearic acid or oleic acid to the base oil, the crawling phenomenon can be completely eliminated.

4. System leakage
Leakage in the hydraulic system leads to insufficient working pressure, decreased working speed, and power loss in the machine tool. Moreover, external leakage pollutes the environment. Therefore, corresponding measures should be taken to reduce internal leakage and eliminate external leakage. The main reasons for leakage in hydraulic systems are due to poor installation of sealing components, poor processing of sealing ring grooves and sealing components, aging or damage of sealing components, high oil temperature and decreased viscosity, etc.

The main measures to eliminate system leaks include: properly installing sealing components to avoid losing the sealing effect due to sharp edges, burrs, etc. of the parts being cut off; Timely replace aging or damaged sealing components; When rotating sealing components, it is necessary to prevent both high-pressure oil leakage and air from entering the interior; Choose sealing rings with good sealing performance, such as cowhide rings, copper sheets, etc., as sealing devices.