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Room 1803, 2nd, 2501 Lane, Guyang North Road, Songjiang District, Shanghai, China

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Common Faults and Handling Methods of CNC Press Brake(1)

A. the oil pump noise is too loud (heat too fast), the oil pump is damaged

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

2. The oil temperature is too low, the viscosity of the oil is too large, resulting in large oil absorption resistance

3. The oil suction filter is blocked and the oil is dirty.

4. Pump damage (injured during pump installation) caused by barbaric operation

5. Coupling installation problems, such as axial overtightening, motor shaft and oil pump shaft are not the same

6. After the pump is installed, the machine will be reversed for a long time or not refueled.

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

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

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

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

11. The oil temperature is too high, resulting in a decrease in viscosity (within 60 ° C)

12. Hydraulic oil contains water, which will cause high-pressure filter plugging damage.


B. the system can not build up without pressure or pressure

1 oil pump steering error or oil pump damage

2. Is the pressure gauge damaged?

3. The pressure control valve has no electric signal or valve blockage

4. Pressure cartridge valve plug, card, can not seal oil

5. The filling valve is stuck (the slider is not slow)

6. The compensation amplifier is too small.

7. The pressure can only reach a certain value, and the method of directly giving 24V to judge whether there is a problem with the valve oil pump


C. the pressure is built slowly (REXROTH hydraulic system)

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

2. The cartridge valve at the pressure valve may not be flexible

3. Electrically possible problems: use the voltage test directly to the electromagnetic pressure valve 24V, or use the electromagnetic pressure valve spool test. 4. Is the high-pressure oil filter blocked?


D. there is a shock when going down

1. Impact sound caused by looseness of the guide rail

2. The position of the black chip of the grating ruler is incorrect.

3, fast down before the delay parameter setting value is too small


E. the slider has no quick action

1 fast valve has no electric signal or stuck

2. Electromagnetic proportional reversing valve has no electric signal or the spool has no action, stuck (check feedback voltage)

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

4. The filling valve is closed and cannot be opened, so that it can not absorb oil.

5. Scale rule problem

6. Is the footswitch intact, check the wiring

7. After the slow valve is energized, the filling valve is closed, and the upper chamber cannot absorb oil.


F. the slider speed conversion point has a long pause time

1 Intake air in the upper chamber of the cylinder, the pressure build-up time is long (leakage from the self-priming line)

2. The flow rate of the filling valve or the self-priming pipe is small, or the speed of the slider is too fast and the vacuum is sucked.

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

4. After the lower valve is energized, the filling valve is closed, and the upper chamber cannot absorb oil.

5. The neutral position of the proportional valve causes the opening to be different and goes out of sync.

6. Will the speed of the fast down test be paused?

7. The magnitude of the fast down pressure affects the closing of the filling valve, eliminating the rapid down-force

8. Pressure parameter adjustment in the delay stage before the work

9. The filling valve control line damping hole is too small to form a pressure difference

10. CNC system parameters (slow down delay)

11. CNC system parameters (slow down gain parameter reduction)


G. the slider does not slow down

1Electromagnetic proportional reversing valve has no electric signal or the spool has no action, stuck

2. The system cannot establish pressure

3. The filling valve is stuck, or the filling valve seal leaks.

4. Slow down the valve with or without electric signal or stuck

5. The backpressure is too high or the pressure is too low.


H. When the slider moves slowly, it will vibrate, swing, and have noise.

1 cylinder discharge pressure oil contains bubbles

2. The friction of the slider guide is too large, and there is no lubricant.

3. The gap between the rail plate fitting surface is large, or the upper and lower sides are uneven

4. The rack and workbench levels are not adjusted well.

5. Balance valve blockage

6. Check if the quick lower valve is energized to open

7. CNC system parameters (gain), or work speed setting too large

8. The back pressure valve is loose and the resistance on both sides is different.

9. Is the electromagnetic proportional valve coil biased, and the proportional valve neutral signal is correct?

10. Is the signal of the proportional servo valve interfered? The inspection method is the same as above.

11. The cylinder seal ring locks the piston rod, and the resistance is large (for the test of PTFE hard seal ring)

12. The spherical washer on the scale is not installed, the movement of the slide is not smooth, and there is a problem with the communication line of the scale.

13. The pressure curve is wrong, and the pressure is not enough when entering the work.

14. Filling valve pressure seal O-ring produces a small amount of leakage


I. the synchronization deviation is slow when slow

1 synchronous detection system failure (grating ruler)

2. Proportional direction reversing valve

3. Quick valve leakage

4. The back pressure difference between the two sides is large

5. The oil temperature is too low

6. Oil cylinders in the upper and lower chambers

7. CNC system parameters

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Room 1803, 2nd, 2501 Lane, Guyang North Road, Songjiang District, Shanghai, China