Fault analysis and troubleshooting of hydraulic system of sheet bending machine

There are many kinds of hydraulic system failures. Some of these failures are caused by the failure of a hydraulic component. Some are caused by the combination of multiple components in the system; Some are caused by improper selection of hydraulic oil and hydraulic oil pollution; Some are also caused by mechanical, electrical and external factors .

Some of these failures occur after a slow build-up, but many occur suddenly. Many users of hydraulic equipment do not pay attention to equipment maintenance and can only be repaired after the equipment has broken down. In order to catch up with the construction cycle or pursue economic benefits, they even make the equipment work with the disease, thus greatly reducing the use time of the equipment sheet bending machine.

Usually, it takes less than half a day and more than a few days to troubleshoot hydraulic equipment. Users were so worried that some had to buy new machines. Hydraulic technology is a new technology and not easy to master bending machine.

So, how can maintenance personnel with little knowledge of hydraulic technology analyze and find faults as quickly as possible without special instruments?

Taking "hydraulic system of multi-function bending machine" as an example, the troubleshooting method is discussed.

This machine is used for bending processing of metal material products with diameter φ 4.5 ~ ф 12mm. It is composed of three parts: main engine, hydraulic station and electrical control cabinet. The hydraulic principle is shown in Figure 1.

1 - filter; 2, 3 - dual hydraulic pump; 4, 16-position two-way solenoid directional valve; 5,6 - pilot type relief valve; 7, 12-three four-way solenoid directional valve; 8,11 - one-way throttle valve; 9 - Left bending mechanism hydraulic cylinder; 10 - Right bending mechanism hydraulic cylinder; 13 - Press the hydraulic cylinder; 14-two four-way solenoid directional valve; 15 - Speed control valve

Common faults during operation of the equipment include:

First of all, the noise increases suddenly and the working pressure decreases.

1) Check whether there are bubbles in the compressor oil of the car oil tank, if there are bubbles, it is because the system software enters the vapor body; If not, go to 2).

By observing whether there are two kinds of bubbles in the compressor oil, this is a layer of large bubbles on the surface, basically no compressor oil; The other is the compressor oil with a small bubble.

The reasons for the first type of steam inlet are: the oil inlet plastic hose of the hydraulic pump leaks; Hydraulic seal of connection head is damaged; Hydraulic oil pump shaft skeleton seal damage (the former probability is greater).

Solution: remove the plastic hose into the oil; Remove the hydraulic seal of the connection head; Remove the hydraulic pump shaft skeleton seal.

The second type of air intake is because the filter screen 1 is blocked or deoiled plastic hose embrittlement.

Solution: clean or remove the filter screen 1 or remove the oil plastic hose (must be changed to acid and alkali resistant plastic hose), if the compressor oil is dirty, be sure to remove the same model specifications of new gear oil.

2) Adjust the speed control valve 6 and 5, add the system software rating load, touch the hydraulic pump 2 and 3 by hand, if the temperature rises rapidly and the vibration is abnormal, indicating the internal parts of the pump damage.

Solution: Replace pump or repair.

Secondly, the system software has no noise and no working pressure. First check whether the remaining oil of the oil return port of the system software is normal. If everything is normal, then in 5,6 2 speed control valve side listen to whether there is the sound of the compressor lubricating oil flow, if there is, distinguish which one, that is the speed control valve is abnormal, clear only; If the remaining oil returned to the oil hole is abnormal, it indicates that the pump is destroyed, repair the pump or replace the pump.

Finally, the system software has no noise. When the gear oil temperature is low, the working pressure is normal. When the temperature is high, the working pressure is reduced.

This common fault is not very easy to distinguish and deal with in the basic way, can be handled by section enumeration method: the first analysis from the hydraulic schematic diagram, the system software is divided into three subsystems (1 hydraulic cylinder control loop is counted as 1), electrohydraulic directional valve 7 subsystem is by the pump 2 supply and demand balance working pressure oil; The two sub-systems of electro-hydraulic directional valve 12 and 14 are supplied by pump 3 to balance the working pressure oil. The following two parts are discussed.

Advance preparation criteria:

When the operating temperature of the system software is over normal, the common fault of reducing the working pressure appears. The system software uses the hydraulic directional valve connected with flat plate (if the hydraulic directional valve connected with bolts can also refer to this method to distinguish);

According to the specifications of installation holes and oil inlet and outlet holes of the electro-hydraulic directional valve (4,7,12,14, etc.), produce and process four block plates with a thickness of 12mm, and install the O-type sealing ring at the oil inlet and outlet.

The sub-system of the control of the electro-hydraulic directional valve 7 is discussed.

1) Shut down the server, and plug the electro-hydraulic reversing valve 7 with the relative plugging plate, so that oil leakage can not be allowed. Then, start pump 2 to see if the working pressure rises to the rated current. If not, go to 2); If more than, indicates that the electro-hydraulic valve or hydraulic cylinder leakage. Check the hydraulic cylinder first. Method: Remove the plug plate of the modified electro-hydraulic reversing valve 7, replace the electro-hydraulic reversing valve 7, remove the rodless cavity inlet of the hydraulic cylinder 9 together (assuming that the hydraulic cylinder has been returned), start the hydraulic oil pump, make 2YA get electricity, and see whether the oil seepage from the disassembled hydraulic cylinder connection head. If it leaks, it indicates that the hydraulic seal on the piston rod of the hydraulic cylinder 9 is damaged and needs to be replaced; If it does not leak, there is no doubt that it is a common fault caused by leakage in the electro-hydraulic directional valve 7. The new electro-hydraulic directional valve of the same model can only be replaced.

2) Remove the speed control valve 6 of the same model. If the working pressure is rated current, it indicates that the valve is damaged and needs to be removed. Otherwise, it is a common fault caused by the embrittlement of hydraulic oil pump 2, and the pump of the same model needs to be replaced.

Check 2 sub-systems of pump 3 driver.

1) Shut down the main engine, and plug the electro-hydraulic reversing valve 12 with the relative blocking plate, so that oil can not seep. Start pump 3 to see whether the working pressure of the system software is the rated current. If it exceeds the rated current, please refer to 1) method in hydraulic directional valve 7 for inspection; If not, go to this section mode 2).

2) Shut down the server, and plug the electro-hydraulic reversing valve 14 with the relative plugging plate, so that oil leakage can not be allowed. At this time, the block plate at part 12 of the electro-hydraulic directional valve is still in the system software. Start the pump 3 to see whether the working pressure of the system software is the rated current. If it exceeds the rated current, please refer to method 1) in hydraulic directional valve 7 for inspection. If not, go to this section mode 3).

3) Shut down the server, and plug the electro-hydraulic reversing valve 4 with the relative plugging plate, so that oil leakage can not be allowed. Start pump 3 to see whether the working pressure of the system software is the rated current. If it exceeds the rated current, it indicates that the electro-hydraulic reversing valve 4 is destroyed and needs to be replaced. If it is not up to it, it must be the embrittlement of hydraulic oil pump 3, which needs to be dismantled and replaced.