Common faults and solutions of CNC bending machines

As the core equipment in sheet metal processing, the efficiency and precision of electro-hydraulic bending machines are crucial to production quality. However, in actual use, affected by operating habits, maintenance level and environmental factors, some faults are inevitable in the equipment. This article classifies and analyzes the common faults of electro-hydraulic bending machines, and provides corresponding solutions to help operators and maintenance personnel quickly locate problems and resume production.

Ⅰ. Abnormal movement of the slider

Fault phenomenon:

The slider cannot move down or up normally, the movement speed is unstable, or it is stuck in the middle.

Cause analysis:

1. Insufficient pressure in the hydraulic system may be caused by wear of the oil pump, improper adjustment of the overflow valve or contamination of the hydraulic oil.

2. The solenoid valve controlling the slider is stuck or the coil is damaged, and the oil circuit cannot be switched normally.

3. The guide rail is poorly lubricated or the gap between the slider and the guide rail is too large, resulting in increased mechanical resistance.

4. The displacement sensor fails and the feedback signal is abnormal, resulting in misjudgment of the control system.

5. The cylinder seal is damaged, causing the piston rod to fail to work.

Solution:

1. Check the hydraulic oil level and oil quality, replace the contaminated oil and clean the oil tank; adjust the overflow valve to the rated pressure.

2. Disassemble the solenoid valve for cleaning or replace the damaged valve core/coil.

3. Clean the guide rail and add special grease, and adjust the guide rail gap to the standard range.

4. Calibrate or replace the displacement sensor, and check whether the signal line connection is reliable.

5. Open the cylinder to check or replace the seal.

Ⅱ. The bending angle deviation is too large

Fault phenomenon:

The angle of the workpiece after processing is inconsistent, the upper and lower molds are not aligned, or there is a unilateral angle deviation.

Cause analysis:

1. The positioning accuracy of the back stop is reduced, which may be due to screw wear or servo motor encoder failure.

2. The mold is loosely installed or the parallelism of the upper and lower molds is not calibrated.

3. The proportional valve in the hydraulic system responds delayed, resulting in uneven pressure distribution.

4. The material thickness or hardness fluctuation exceeds the compensation capacity of the equipment.

Solution:

1. Check the rear stop transmission mechanism, replace the worn screw rod; calibrate the servo motor zero point.

2. Reinstall the mold and use the dial indicator to adjust the parallelism of the upper and lower molds.

3. Clean the proportional valve core or replace the aged valve body to optimize the control parameters.

4. Adjust the pressure compensation parameters according to the material characteristics, or add material testing links.

Ⅲ. Hydraulic system leakage or abnormal noise

Fault phenomenon:

Oil stains appear around the oil tank, and the oil temperature rises abnormally; sharp noise or vibration occurs during operation.

Cause analysis:

1. Loose hydraulic pipe joints or aging seals lead to oil leakage.

2. The hydraulic pump inhales air (the oil level is too low or the oil suction filter is blocked), generating cavitation noise.

3. The overflow valve is in a high-pressure overflow state for a long time, causing the system to overheat.

4. The inner wall of the oil cylinder is scratched or the piston seal fails, causing internal leakage.

Solution:

1. Tighten the pipe joints and replace the O-rings or combined gaskets.

2. Refill the hydraulic oil to the standard liquid level, clean or replace the oil suction filter.

3. Check whether the load exceeds the limit to avoid frequent opening of the overflow valve.

4. Disassemble the oil cylinder to check the seals, and repair or replace damaged parts.

Ⅳ. Electrical control system failure

Fault phenomenon:

The touch screen displays abnormally, the buttons do not respond, or the equipment stops suddenly.

Cause analysis:

1. Poor contact of PLC module input/output points, or burnout of relay contacts.

2. Power supply voltage fluctuations lead to unstable power supply of control system.

3. Emergency stop switch is triggered by mistake or safety light curtain is blocked.

4. Program parameters are lost or software version conflicts.

Solution:

1. Use a multimeter to detect PLC input signal, clean or replace relay.

2. Install a voltage stabilizer and check whether the grounding line is reliable.

3. Reset the emergency stop button and clear obstacles in the light curtain sensing area.

4. Re-import backup parameters and upgrade the control system firmware.

V. Preventive maintenance recommendations

1. Regular maintenance: Replace hydraulic oil and filter element every 12 months, and clean radiator dust.

2. Parameter monitoring: Record operating data such as pressure and temperature, and deal with abnormal trends in time.

3. Accuracy calibration: Check the parallelism of the slider and the repeatability of the back gauge positioning accuracy every month.

4. Train operators: avoid human errors such as overloading and incorrect programming.

Conclusion

The failure of electro-hydraulic bending machines often has the characteristics of multiple causes and one result. Rapid diagnosis requires comprehensive analysis of mechanical, hydraulic and electrical aspects. By standardizing operating procedures and implementing preventive maintenance, the failure rate can be significantly reduced. For complex problems (such as imbalance of the dynamic characteristics of proportional valves), it is recommended to contact the equipment manufacturer or professional engineers for in-depth debugging to ensure long-term stable operation of the equipment. ZYCO is a manufacturer specializing in the design and production of bending machines. If you have any questions about bending machines, you can also contact us. ZYCO's engineering team will help you solve them.