The cause and solution of the slide block on the hydraulic press can not return normally

Hydraulic press has high precision, high safety, low noise and other characteristics, but there will be failures when in use, today Jianlong small series on the hydraulic press slider can not normal return detailed, come and take a look.

1. Description of the fault site. It runs normally at the beginning of work, and after working for a period of time, the upper slider can not return, the return button command is invalid, and the machine can not run normally.

2. Fault analysis. Before analyzing the fault, the working principle of the hydraulic press during the return trip is described briefly: the slider relies on the oil inlet line of the return cylinder to generate the upward lifting force and the discharge line of the main oil cylinder to achieve the return trip. During the working process of the hydraulic press, the slide block fails to return, indicating that the slide block goes down normally and the return trip is abnormal, that is, the oil inlet pipeline of the main cylinder is normal when the slide block goes down, and the oil return of the main cylinder and the oil inlet of the return cylinder may be abnormal when the slide block returns. In addition, the input and output points of the electrical control system may be abnormal during the return trip of the slider, and the fault tree method is also adopted to make the fault problems organized.

3. Fault diagnosis. First of all, the application of SLC500 PLC online monitoring function check each control point and control valve input and output is normal, check found that the input and output are normal, it has been proved that there is no abnormality in electrical control, the fault problem stems from the hydraulic system, the problem point is concentrated in the main oil cylinder return pipeline and return cylinder oil pipeline. Then, check whether the electromagnetic reversing valve and the electromagnetic reversing valve in the two pipelines are normal, and the electromagnetic reversing valve moves the main valve core and communicates with the control oil circuit through the gain and loss of power, so as to achieve the rise and fall of the slide block and the return trip of the return cylinder.

It is found that the reversing action and sound of the electromagnetic reversing valve and the electromagnetic reversing valve are normal, and the cause of the fault caused by the electromagnetic reversing valve is basically eliminated. In order to further confirm the fault point, when the slider is returning, the pressure gauge pointer reading and pressure relief pressure gauge are controlled remotely to determine that the main cylinder return pipeline is normal. The problem point is finally locked in the return cylinder oil intake pipeline, if the return cylinder does not feed oil or the pressure is not enough, it may affect the slide block can not return, if the hydraulic control check valve is the reason, there are two cases of spool stuck and spring failure.

Disassembly and inspection of the hydraulic check valve found that the spool was abnormal and the spring was damaged. In order to improve the maintenance speed, the hydraulic check valve of the same model was replaced, but the fault was not completely solved, so it was determined that there were problems with the relief valve at the same time. After inspection, it was found that the spool of the relief valve operated normally, but the internal spring was damaged, the pressure regulating effect of the relief valve failed, the return cylinder could not establish the return pressure, and the slide block could not return. Finally repair the relief valve, troubleshooting.

4. Correction and prevention. For this kind of failure involves many reasons and some complex, it is necessary to analyze and troubleshoot layer by layer, and use known machine tool information as far as possible to eliminate interference factors and determine the cause of the fault. In view of the failure of the control valve, the spool stuck is caused by the wear of the spool, the blockage of oil pollution and impurities, and the rust of the spool caused by water in the oil. The spring damage is caused by the low strength of the spring, aging and wear, poor control valve pressure setting, and the spool stuck. In daily maintenance, it is necessary to pay special attention to the occurrence of the above adverse conditions and make full use of the PLC self-diagnosis function.