1. Excessive noise (rapid heating) and damage to the oil pump
1. Air leakage in the oil pump suction pipeline or low oil level in the tank causing the oil pump to draw in air.
2. Low oil temperature and high viscosity of the oil causing increased suction resistance.
3. Clogging of the oil filter at the suction port and dirty oil.
4. Pump damage (injury during pump installation) due to any impact.
5. Coupling installation issues, such as excessive axial tightness or misalignment between the motor shaft and oil pump shaft.
6. Prolonged reverse rotation or lack of oil during pump testing after installation.
7. Blockage of the high-pressure outlet filter or failure to achieve the required flow rate.
8. Oil pump cavitation (presence of air at the oil pump suction port despite the presence of oil).
9. For piston pumps, it could be due to the low height setting of the return oil port pipeline.
10. For HOEBIGER pumps, air release may be required.
11. High oil temperature leading to decreased viscosity (within 60°C).
12. Presence of water in the hydraulic oil leading to blockage and damage to the high-pressure filter element.
2. Lack of system pressure or inability to build up pressure
1. Incorrect rotation direction of the oil pump or pump damage.
2. Possible damage to the pressure gauge.
3. Presence of electrical signal or blockage in the pressure control valve.
4. Blockage or improper sealing of the pressure cartridge valve.
5. Sticking of the filling valve (no slow descent of the slide).
6. Insufficient adjustment of the compensator amplifier.
7. If the pressure can only reach a certain value, use a direct 24V method to determine if there is a problem with the valve or pump.
3. Slow pressure build-up (REXROTH hydraulic system)
1. The damping hole at the X port of the pressure valve may be blocked.
2. The cartridge valve at the pressure valve may have poor responsiveness.
3. Possible electrical issues: Test the electromagnetic pressure valve with a direct 24V voltage or test the valve core with an object.
4. Check for blockage in the high-pressure oil filter.
Four: Impact noise during rapid descent
1. Impact noise caused by loose guide rails.
2. Incorrect position of the grating ruler black plate.
3. Delay parameter setting for rapid descent is too small.
Five: Lack of rapid descent action in the slide
1. Check for electrical signals or blockage in the rapid descent valve.
2. Check for electrical signals or movement of the electromagnetic proportional directional valve, or if it is stuck (check feedback voltage).
3. Mechanical parts are too tightly connected, such as overly tight guide rails or cylinder.
4. Filling valve is closed and unable to open, resulting in inability to draw oil.
5. Issues with the grating ruler.
6. Check the condition of the foot switch and inspect the wiring.
7. After the slow descent valve is energized, the filling valve is closed, causing the upper chamber to be unable to draw oil.
Six: Long pause time at the speed conversion point of the slide
1. Air intake in the upper chamber of the cylinder, resulting in a longer pressure build-up time (air leakage in the self-priming pipeline).
2. Insufficient flow in the filling valve or self-priming pipeline, or excessive vacuum caused by too fast rapid descent of the slide.
3. The filling valve is not completely closed, resulting in slow pressure reduction in the upper chamber.
4. After the slow descent valve is energized, the filling valve is closed, causing the upper chamber to be unable to draw oil.
5. Incorrect positioning of the proportional valve, causing different openings and asynchronous movement.
6. Test by reducing the rapid descent speed to see if there is a pause.
7. The size of the rapid descent pressure affects the closing of the filling valve, eliminate the rapid descent pressure.
8. Adjust the pressure parameters during the pre-delay stage of the work advance.
9. The damping hole in the control circuit of the filling valve is too small, causing pressure difference.
10. CNC system parameters (pre-delay for slow descent).
11. CNC system parameters (decrease in gain parameter for slow descent).
Seven: No slow descent action in the slide
1. Check for electrical signals or blockage in the electromagnetic proportional directional valve.
2. System unable to build pressure.
3. Filling valve is stuck or the sealing ring of the filling valve is leaking.
4. Check for electrical signals or blockage in the slow descent valve.
5. Excessive back pressure or too low slow descent pressure.
Eight: Vibration, swinging, and noise during slow descent motion of the slide
1. Presence of air bubbles in the pressure oil discharged from the cylinder.
2. Excessive friction in the slide guide rails, lack of lubricating oil.
3. Large clearances or uneven alignment in the mating surfaces of the guide rails.
4. Poor adjustment of the frame and worktable level.
5. Blockage in the balance valve.
6. Check if the rapid descent valve is energized and open.
7. CNC system parameters (gain) or excessive work advance speed setting.
8. Loose back pressure valve, uneven resistance on both sides.
9. Coil bias in the electromagnetic proportional valve, incorrect mid-position signal of the proportional valve.
10. Interference with the signal of the proportional servo valve, use the same inspection method as above.
11. Sealing ring of the cylinder gripping the piston rod tightly, causing high resistance (test by replacing with polytetrafluoroethylene hard sealing ring).
12. Missing spherical gasket on the grating ruler, resulting in unsmooth movement of the slide and communication line issues with the grating ruler.
13. Incorrect pressure curve, insufficient pressure during work advance.
14. Minimal leakage from the pressure sealing O-ring of the filling valve.
Nine: Large synchronization deviation during slow descent
1. Faults in the synchronization detection system (grating ruler).
2. Proportional directional valve.
3. Leakage in the rapid descent valve.
4. Large difference in back pressure on both sides.
5. Low oil temperature.
6. Oil leakage between the upper and lower chambers of the cylinder.
7. CNC system parameters.
Ten: Oscillation and jitter during dead point holding of the slide
1. Possible issues with the grating ruler.
2. Presence of air bubbles in the pressure oil discharged from the cylinder.
3. Blockage in the balance valve.
4. CNC system parameters (gain).
5. Back pressure valve issues, uneven resistance on both sides.
6. Problems with the electromagnetic proportional valve: Incorrect mid-position.
7. Loose fastening bolts of the cylinder → Jitter at the dead point, incorrect height, inaccurate bending angle, and noise during bending.
Eleven: No return action or slow return of the slide
1. Check for direction change and possible damage in the electromagnetic proportional directional valve.
2. Check if the system has established pressure or if the return pressure is too low.
3. One side of the filling valve may be stuck or not fully open.
4. After the slow descent valve is energized, the filling valve is closed, preventing rapid return.
5. CNC system: Programming angle is too small, unable to reach the bending programming dead point.
6. Zero adjustment of CNC system parameters.
7. Damage to the grating ruler or wiring issues.
8. Check if the system pressure builds up slowly.
Twelve: Vibration and jitter during return motion of the slide
1. Excessive or insufficient return pressure.
2. System parameters or PLC and DM02 module.
3. Coil deviation in the proportional valve.
Thirteen: Slide sliding down (upper dead point)
1. Adjustment of the back pressure valve.
2. Leakage in the back pressure valve or rapid descent valve.
3. Oil leakage between the upper and lower chambers of the cylinder.
4. Bias in the proportional valve.
5. Insufficient stability of the supporting sealing ring, leading to slide sliding after deformation.
6. Determine the cause of sliding - observe if oil comes out from the lower chamber oil port after removing the proportional valve.
Fourteen: Large bending angle error
1. Check if the compensating cylinder has excessive deflection and cannot fully return to the zero position.
2. Check if the quick clamping wedge is loose.
3. Check if there are changes in the lower dead point during each bending.
4. Check if the installation of the arch-shaped handle is in compliance and if the screw holes are fully tightened.
5. Changes in the sheet material itself (thickness, material, stress).
6. Check if the grating ruler is loose.
7. Inaccurate positioning: Check if the zero offset value of the proportional valve is appropriate, as positioning cannot reach the lower dead point, resulting in inability to return.
Fifteen: Large straightness error in bending
1. Check if the compensating cylinder has appropriate deflection.
2. Check if the quick clamping wedge is loose.
3. Check if there is deformation in the horizontal and vertical mating surfaces of the slide.
4. Check if there is deformation in the upper and lower molds.
5. Changes in the sheet material itself (thickness, material, stress).
6. Check if the lower worktable (neutral plate) is deformed.
Sixteen: Hydraulic pipeline oil leakage or pipe burst
1. Check if the oil pipe installation meets the requirements (extension length, diameter, wall thickness, clamps, nut tightness, bending radius, etc.).
2. Check if there is any impact or vibration on the oil pipe.
3. Check if the pipeline interferes with other components, causing collisions.
4. Lack of pipe clamps for fixing the pipeline.
Seventeen: Precautions for hydraulic system installation and maintenance:
1. Valves sealed with paint should not be disassembled or adjusted by oneself.
2. After the valves are cleaned and functioning properly, new oil must be immediately replaced and the oil tank cleaned.
3. The oil pump should not be subjected to any impact or shock during installation, and it should be pre-filled with oil before testing.
4. During installation, only handle the valve body of each valve, and do not touch any solenoid valves.
Eighteen: Common analysis of faults in the back gauge
1. Back gauge unable to move: ① Check if the driver has an alarm.
② Check the limit switches of each axis.
③ Check the reliability of the connectors.
2. Alarm from the driver.
3. Unstable and jittery movement of the X and R axes.
4. Changes in positioning accuracy: ① Mechanical issues (looseness, impact).
② Electrical - unidirectional positioning.
③ Parameter adjustment.
④ Check if the tensioning wheel is loose and if the screw connecting the lead screw is loose.
5. Overload alarm: Check if the ball screw can rotate easily, as the steel balls may be damaged.
6. Alarm 16 from the R-axis driver → Faulty gas spring.
7. Alarm 22 from the Z1 and Z2 axes → Replace the encoder cable.
8. Alarm 38 → Loose connection in the wiring joint.
9. Servo motor emits noise: Gain setting is too high.
