Troubleshootings for Hydraulic Press Brake Machine

For most of the press brake operators, they will encounter some problems on the hydraulic press brake machines. Sometimes, it will take long time for the new novices to fix them, today we will share some details and solutions with you and hope it will be helpful to you.

Trouble 1: No pressure in the hydraulic system of the hydraulic press brake or the pressure button does not work

1. Whether the solenoid coil of the proportional relief valve is energized and whether the voltage of the proportional solenoid coil meets the requirements. If it is due to the above reasons, please check the related electrical reasons.

2. Check whether the cartridge valve or the main spool is stuck and the damping hole is blocked. If it is related to the cause, please disassemble the overflow valve and clean it, and then reinstall it.

3. The phase adjustment of the three-phase power supply causes the motor to reverse.

4. The oil pump rotates incorrectly or the oil pump is damaged.

5. Whether the pressure gauge is damaged.

6. Whether the pressure control valve has electrical signal or valve blockage.

7. The pressure cartridge valve is blocked or stuck and cannot seal the oil.

8. The filling valve is stuck (the ram does not slow down).

9. The compensation amplifier is adjusted too small.

10. When the pressure can only reach a certain value, use the method of directly supplying 24V electricity to judge whether there is a problem with the valve oil pump.

Trouble 2: Long pause time at the speed change point of the ram 

1. The upper cavity of the oil cylinder sucks in air, and the pressure builds up for a long time (the self-priming pipeline leaks).

2. The flow rate of the filling valve or self-priming pipeline is small, or the sliding speed is too fast to cause suction.

3. The filling valve is not completely closed, and the pressure in the upper cavity slows down.

4. After the slow down valve is energized, close the filling valve, and the upper cavity cannot suck oil.

5. The wrong position of the proportional valve leads to different openings and out of synchronization.

6. Decrease the fast down speed and check whether the test stops.

7. The size of the fast down pressure has an effect on the closing of the filling valve and eliminates the fast down pressure.

8. Adjust the pressure parameters in the delay stage before work advance.

9. The damping hole of the filling valve control line is too small, resulting in a pressure difference.

10. CNC system parameters (delay before slow down).

11. CNC system parameters (the gain parameter decreases at slower speed).

12. Check whether the oil level of the fuel tank is too low and the filling port is not flooded. When fast forward, the upper cavity of the cylinder is filled with liquid, causing insufficient filling. For the above reasons, add oil from the tank to more than 5mm above the filling port so that the filling hole is completely flooded.

13. Check whether the filling valve is fully opened. If it is because of oil contamination, the valve core of the filling valve is not flexible and jammed, causing insufficient filling. The filling valve needs to be cleaned and reinstalled to make the spool flexible.

14. Check whether the fast forward speed is too fast, causing insufficient filling. For the above reasons, the fast forward speed can be reduced by modifying the system parameters.

Trouble 3: The return speed of the hydraulic press brake ram is normal, the fast forward speed is normal, The ram can not come down in manual mode and no enough bending force. 

1. Check whether the "three-position four-way" reversing valve of the control filling control oil circuit is working properly, if it is, the filling valve is not closed, so that the upper cavity is connected to the filling port of the fuel tank, and pressure cannot be built. The reason that the valve cannot work normally is that it is not powered on or is stuck.

2. Check whether the filling valve is stuck. If so, please clean the filling valve and reinstall it to make the valve core flexible.

Trouble 4: The return speed of the hydraulic bending machine ram is too slow, and the return pressure is high

This type of Trouble is mainly caused by the fact that the filling valve is not opened. This phenomenon is just the opposite of the logical relationship of the above-mentioned Trouble three. It can be dealt with by referring to the solution of Trouble three.

Trouble 5: The ram is not vertical when it is working, and it makes abnormal noises

This type of failure is due to the long use of the guide rail, abnormal lubrication of the guide rail, and increased clearance due to wear. It is necessary to check the wear degree of the guide rail pressure plate and readjust to meet the required clearance. Depending on the degree of wear, determine whether to replace the rail pressure plate. If the strain is severe, it needs to be replaced.

1. The original pressure plate is pasted with plastic. Pay attention to the hardness of the pasted plastic and the pasting surface of the guide rail. After scraping, ensure that the pasting surface is above 85%, and open a zigzag lubricating oil groove;

2. Inside the original pressure plate is a metal plug iron. To choose tin bronze plate or ductile iron, the bonding surface is processed by a grinder, the connecting bolt is lower than the bonding surface, and a zigzag lubricating oil groove is opened.

Trouble 6: The bending machine ram can only go down, and there are many situations that can not go up

● There is no pressure on the return stroke, and the ram of the bending machine cannot go up:

1. Circuit problems.

2. The pressure regulating valve is stuck.

●  There is pressure on the return stroke, and the ram of the bending machine cannot go up:

1. If the pressure is small, increase the pressure.

2. The reversing valve is stuck

●  The return pressure is very large, and the ram of the bending machine rises slowly:

1. The hydraulic control valve is stuck.

2. The oil pressure of the hydraulic control is too low.

3. The control oil reversing valve is stuck or does not change direction.

4. The solenoid valve spool is reversed

●  It can rise and fall without pressure or for a long time before pressure: 

1. For electrical circuit problems, the solenoid valve must not be powered.

2. The large hydraulic control valve spring and the spool are damaged.

3. The lifting cylinder screw falls off.

●  The machine tool declines:

1. Circuit problems.

2. The oil cylinder sealing ring is damaged. Does not lock the oil.

3. The oil circuit of the locking device is leaked and damaged. (Small hydraulic control, throttle valve, etc., depending on the hydraulic system of the machine tool)

●  The machine tool drops slowly or jitters:

1. The oil cylinder is roughened, damaged or the nut screw in the oil cylinder is stuck.

2. The track is worn or not vertical.

Trouble 7: There is an impact sound when the ram moves quickly 

1. Impact sound caused by loose rail plate.

2. The position of the grating ruler is incorrect or the position of the travel switch is incorrect.

3. The setting value of the delay parameter before fast down is too smal

Trouble 8: The ram can not move down quickly

1. Whether there is an electrical signal or stuck in the quick lower valve.

2. Whether the electromagnetic proportional directional valve has an electrical signal or whether the spool is moving or stuck (check the feedback voltage).

3. The mechanical part is connected too tightly, such as the guide rail plate is too tight, and the cylinder is too tight.

4. The filling valve is closed and cannot be opened, so no oil can be sucked.

5. Grating ruler problem.

6. Check whether the foot switch is in good condition, check the wiring.

7. After the slow down valve is energized, close the filling valve and the upper cavity cannot suck oil.

Trouble 9: The ram can not move down slowly

1. Whether the electromagnetic proportional directional valve has an electrical signal or whether the spool is moving or stuck.

2. The system cannot build pressure.

3. The filling valve is stuck, or the filling valve sealing ring is leaking.

Trouble 10: The size of the backgauge is inconsistent at both ends (small and large ends)

The error at both ends is small, within 2mm. Check to confirm that the X1/X2 mechanical transmission structure has no Troubles. The error can be eliminated by adjusting the finger fine adjustment. If there are no Troubles in the mechanical transmission structure (such as bearings, ball screws, linear rails, transmission wheels, transmission belts, etc.), remove the Trouble. Re-adjust to within the tolerance of parallelism and re-install the synchronous transmission device.

Trouble 11: No action on the backgauge axis

The reason for the failure of the backgauge shaft transmission may be that the transmission shaft is separated from the timing belt wheel, the key bar or the timing belt slips off. The stopper shaft driver and servo motor are Trouble, and the upper computer control system is Trouble. Such failures need to check and confirm the cause of the failure, repair or replace the Trouble components, and eliminate the failure.

Trouble 12: Connection between cylinder and ram is loose

Loose connection between the oil cylinder and the sliding block may cause the bending angle to be inaccurate or the machine cannot find the reference point.

Trouble 13: The oil pump is too noisy (heats too fast), the oil pump is damaged

1. The oil pump suction line leaks or the oil tank liquid level is too low, causing the oil pump to suck.

2. The oil temperature is too low and the oil viscosity is too high, resulting in high oil absorption resistance.

3. The suction port oil filter is clogged and the oil is dirty.

4. Pump damage (injury when installing the pump) by any knock.

5. Coupling installation problems, such as excessive axial tightening, the motor shaft and the oil pump shaft are not concentric.

6. After the pump is installed, it reverses for a long time or does not refuel during the test machine.

7. The outlet high pressure oil filter is blocked or the flow rate is not up to the standard.

8. The oil pump sucks (there is oil, but there is air at the oil pump suction port).

9. If it is a plunger pump, the height of the return line may be set too low.

10. If it is a HOEBIGER oil pump, it may be deflated.

11. The oil temperature is too high, causing the viscosity to decrease (within 60°C).

12. Hydraulic oil contains water, which can cause blockage and damage to the high-pressure filter element.

Trouble 14: Generating pressure is too slow (REXROTH hydraulic system)

1. The orifice at port X of the pressure valve may be blocked.

2. The cartridge valve at the pressure valve may not move flexibly.

3. Possible electrical problems: use the 24V voltage test directly to the solenoid pressure valve, or use something to test the solenoid pressure valve spool.

4. Is the high-pressure oil filter blocked