Bending machines may encounter various failures during use. This article summarizes the cause analysis and solutions of common failures to help operators quickly troubleshoot and deal with problems.
1. The main motor does not rotate
Cause analysis
- Starting circuit failure: emergency button is not released, cable connection is loose, 24V control power supply is abnormal
- Motor starting component problem: thermal relay, circuit breaker, AC contactor and other overload protection or damage
- Power supply problem: three-phase power supply is abnormal
Solution
- Check the emergency button status, confirm that the cable connector is firmly connected, and verify whether the 24V control power supply is normal
- Check whether the main motor starting component is in overload protection state, and replace damaged components if necessary
- Check whether the three-phase power supply is intact and the voltage is balanced
2. The cam cannot drop quickly
Cause analysis
- The cam rail is too tight
- The rear stopper shaft is not in place
- The cam has not run to the dead point position
- The signal of the foot switch and other components has not entered the control module
- Proportional servo valve failure
Solution
- Check and adjust the tightness of the cam rail
- Check whether there is a cursor on the actual position of the X-axis on the controller, and verify whether the rear stopper programming value on the manual interface is consistent with the actual value
- Confirm that the Y-axis state is “1” (if it is “6”, detect the actual coordinate of the Y-axis, which should be less than the difference between the Y-axis and the return stroke)
- Check whether the signal transmission of the foot switch and other components is normal
- Check the feedback signal of the proportional servo valve
3. The cam did not reach the predetermined bending position
Cause analysis
- The cam did not reach the transition point
- Improper setting of Y-axis bending parameters
- Insufficient pressure (programming operation, parameter setting or hydraulic system problem)
Solution
- Check whether the Y-axis status changes from “2” to “3”, confirm that the actual value of the Y-axis should be greater than the conversion value, and adjust the fast forward parameter if necessary
- Re-adjust the Y-axis bending parameters
- Use a pressure gauge and a multimeter to check the main pressure and proportional pressure valve signals, check whether the valve is blocked, check the filter element and hydraulic oil status, and check the oil pump and coupling if necessary
4. Cam cannot return
Cause analysis
- Cannot return without load: parameter setting error or hydraulic oil failure
- Cannot return when bending workpiece: workpiece angle does not reach the preset value
- Cannot return but workpiece angle exceeds the preset value
Solution
- Debug Y-axis bending parameters: too small gain will lead to incomplete bending, too large will cause jitter; check the left and right valve offset settings and main pressure, and confirm the PV valve S5 status
- Appropriately increase parameter gain; check whether the pressure is sufficient; analyze program design (mold, plate thickness, material, workpiece length, bending method) and hydraulic system (oil pump, pressure valve, filter element, hydraulic oil)
- Check all program settings and workpiece parameters
5. The slider does not run smoothly
Cause analysis
- Loose cam guide rail
- Loose cam locking nut
- Machine parameters need to be adjusted
- Proportional servo amplifier zero offset
- Improper back valve pressure setting or uneven pressure on both sides
Solution
- Re-adjust the guide rail gap
- Re-tighten the nut and replace it if it does not match
- Adjust machine parameters according to the reference curve
- Carefully adjust the BOSCH or REXROTH valve
- Use a pressure gauge to adjust the back pressure valve to ensure that the pressure on both sides is consistent
6. The main motor stops working automatically
Cause analysis
- The proportional pressure valve and the total pressure relief valve are blocked, resulting in continuous pressurization
- The filter is blocked and affects the oil circuit
- The hydraulic oil is contaminated or of poor quality
- The circuit breaker and thermal relay are faulty
- The system pressure control signal is abnormal
Solution
- Cleaning the pressure gauge valve and the main pressure relief valve
- Replace the filter and check the oil contamination degree
- Replace the engine oil and filter element in time
- Use the recommended high-quality hydraulic oil
- Replace the circuit breaker or thermal relay
- Check the system output signal
7. The hydraulic oil turns black and foams
Cause analysis
- The hydraulic oil has been used for too long and has been contaminated
- Poor oil quality
- Aging of the rubber seal at the oil inlet of the oil tank
Solution
- Regularly replace the hydraulic oil of the bending machine
- Use the high-quality hydraulic oil recommended by the manufacturer
- Replace the oil-resistant rubber seal
8. Bending machine cylinder slips
Cause analysis
- Back pressure valve or drive valve is damaged
- Insufficient back pressure
- SPGO strain and wear
- Cylinder interface strain
- A small amount of slow slip (<0.5mm within 5 minutes) is normal
Solution
- Clean or replace the back pressure valve and drive valve
- Re-adjust the back pressure valve pressure according to the standard
- Replace SPGO and find out the cause of strain and wear
- If the problem is caused by oil contamination, replace the cylinder and seal ring
- No treatment is required for slip within the normal range
9. The height of both sides of the bending machine is inconsistent when pressing
Cause analysis
- The back pressure on both sides is inconsistent, and the back pressure setting may be too high
Solution
- Adjust the pressure on both sides to the specified value and keep it consistent
| Back pressure valve position | Standard pressure value (MPa) | Adjustment method |
|---|---|---|
| Back pressure valve on the left side | 10±0.5 | Clockwise increase, counterclockwise decrease |
| Back pressure valve on the right side | 10±0.5 | Keep consistent with the left side |
10. The slider waits too long at the speed transition point
Cause analysis
- Oil tank suction nozzle leaks
- Oil filling valve failure (improper installation leads to valve core blockage, insufficient spring tension)
- Y-axis feed parameter setting error
Solution
- Check the sealing of the rubber plate and reinstall the cover plate
- Check the installation of the filling valve, valve core movement and spring tension
- Adjust the Y-axis feed parameters
11. The length and angle deviation of the workpiece vary greatly
Cause analysis
- Improper setting of the inertia parameters of the bending machine
- Sheet quality problem
- Multiple bending leads to excessive cumulative error
- Irrational bending sequence
Solution
- Re-adjust the inertia parameters
- Check the sheet quality
- Accurately adjust the accuracy of each bending and control the angle within the negative error range
- Optimize the bending sequence
12. The system calculates that the pressure is greater than the mold resistance
Cause analysis
- Irrational bottom mold selection during programming
- Improper mold resistance setting
- Wrong bending method
- Constant parameters (material parameters, units, etc.) are modified
Solution
- Select a suitable mold according to the relationship between the sheet thickness and the bottom mold opening
- Correctly set the mold resistance of the bending machine
- Check program settings
- Verify the machine constant parameters
13. The large radius bending program is slow to calculate or the system crashes
Cause analysis
- The programmed X valve exceeds the maximum value of the X axis
Solution
- Check and modify the program parameters to ensure that it is within the capacity of the equipment
14. The oil temperature is too high
Cause analysis
- Failure of hydraulic components (filter element blockage, oil contamination or deterioration)
- Long-term high-pressure operation
Solution
- Check the filter element and oil quality and replace them if necessary
- Arrange working hours reasonably to avoid long-term high-load operation
15. The workpiece angle is not accurate
Cause analysis
- Excessive error: incorrect programming, loose slider, damaged grating ruler
- Small error: normal, can be adjusted by the controller
- Unstable angle: loose slider, grating ruler failure or material quality problem
Solution
- Check whether the process parameters (mold, material, thickness, plate length, bending method) are consistent with the actual operation, and check the connection between the slider and the grating ruler
- Appropriately adjust the control parameters to compensate for the error
- Check the Y-axis repeat positioning accuracy and confirm that the slider and grating ruler are connected normally
16. Incorrect workpiece size
Cause analysis
- Unstable size: may be related to power supply, servo system, encoder, controller, mechanical connection, etc.
- Size is deviated but stable: related to the parallelism and straightness of the rear stop beam, the parallelism and verticality of the stopper
- The angle is greater than 90° during the folding edge positioning, resulting in smaller size
Solution
- Check the repeatability of the rear stop axis (should be less than 0.02mm), and check the electrical and mechanical problems one by one
- Check the parallelism, linearity of the beam and the parallelism and verticality of the stopper
- When using the bending edge positioning, the bending angle should be kept less than 90°
Note: Before fault diagnosis and repair, make sure the equipment is powered off and take necessary safety measures. It is recommended to contact professional technicians or equipment manufacturers for complex faults. Regular maintenance and care are the best way to prevent failures.
