Fault Analysis of QC12Y-4×3200 Hydraulic Shearing Machine

1. The tool holder return is too slow to reach the limit position

QC12Y-4×3200 hydraulic shearing machine, the appearance is shown in Figure 1. The working principle of hydraulic oil circuit is shown in Figure 2.

Figure 1——QC12Y-4*3200 Hydraulic Shearing Machine

e 2——Hydraulic oil circuit working principle

The on-site operator reflected that the speed of the shearing machine tool holder was too slow and the upper stop position was lowered, and the problem of restarting the switch was the same. According to the working principle of the hydraulic oil circuit of the shearing machine, the tool return is realized by the return of the nitrogen cylinder on both sides of the fuel tank. Checking the two nitrogen return cylinders, it was found that the two nitrogen pressures were insufficient and the cylinders did not have obvious cracking. The reasons may be related to insufficient nitrogen or abnormality of the nitrogen cylinder seal. After separately adding nitrogen to the two nitrogen cylinders, the pressure gauge of the two nitrogen cylinders was observed after a few minutes, and it was found that the pressure did not change substantially, indicating that the nitrogen cylinder was basically normal, and the pressure of the nitrogen cylinder was pressure drop. When the machine is turned on several times, the speed of the tool holder is still too slow and the upper stop position is lowered. The pressure of the two nitrogen cylinders is basically normal, and the pressure drop of the other is increased. It is initially determined that there is a sealing problem with the nitrogen cylinders with increased pressure drop during operation.

Disassemble the nitrogen cylinder and find that the sealing ring has been severely deformed. Replace the same type of sealing ring. After installation and reset, the machine is turned on, the operation is normal, and the pressure of the two nitrogen cylinders is basically normal. After using it for one month, the same problem reappeared, and a nitrogen cylinder still showed a significant pressure drop. After careful inspection, the seal was deformed again and the seal failed. Observing the nitrogen cylinder sealing structure, it is found that the step surface size of the inner cylinder sealing ring of the nitrogen cylinder bushing (Fig. 3) is too long, and after the sealing ring is repeatedly pressed, it will gradually deviate from the original installation position and deform. The problem lies in the reason why the nitrogen cylinder liner seal ring is installed with the step surface. To completely solve this problem, it is necessary to measure the size of the sleeve and process the corresponding part with the corresponding tolerance. The length of the step surface is determined according to the size of the matching seal ring. After running verification, the problem was solved and the shearer returned to normal.

Figure 3——Nitrogen cylinder bushing

2. After the machine is turned on, the tool holder and the pressing body cannot move.

The on-site operator reported that the knife holder and the pressure body could not move after the shearing machine was turned on. Check that the electrical components of the control circuit are basically normal, and initially determine that the hydraulic system is abnormal. Carefully analyze the hydraulic system of the shearing machine (Fig. 2). After the variable pump starts working, the electromagnetic reversing valve 2 is energized to realize the reversing action. If the electromagnetic reversing valve 2 does not operate, the pressure control valve will be unloaded, resulting in a knife. The rack and the pressure body inlet line have no oil and cannot operate.

First check the operation of the electromagnetic reversing valve 2, the electromagnetic reversing valve works normally and the spool action sounds normal. Depending on the direction of hydraulic oil flow, the cause of the unloading of the pressure control valve is related to the relief valve. If the relief valve is unloaded, it will cause the pressure control valve to unload. Check the relief valve spool and working conditions, no abnormalities were found. The problem may be related to the pressure control valve. Check the cone of the pressure control valve. There is no foreign matter and the spool works smoothly. However, the damping hole on the spool is blocked. After the pressure control valve is damped and reset, the fault is not eliminated.

Further inspection along the flow direction of the hydraulic oil circuit, if the directional control valve 2 is unloaded, it will cause the tool holder and the pressing body to be inoperable. Directional control valve 2 Unloading is related to the operation of the spool and the operation of the solenoid-operated valve 1. Check the directional control valve spool to ensure reliable operation without abnormal conditions. When the electromagnetic reversing valve is not energized, the action is normal and the valve core is not stuck. Carefully check that no other abnormalities were found in the oil circuit, but the tool holder and the pressure body could not move. Further checking the working condition of the variable pump, the variable pump body has no obvious abnormality, but there is a de-soldering condition at the connection between the suction pipe and the pump body inlet port, resulting in insufficient output pressure of the variable pump, causing the tool holder and the pressure body to fail to operate. After repairing the desoldering area, the components of each device are reset and the fault is solved.