Troubleshooting pipe bending machine

During long-term operation, pipe bending machines inevitably experience various malfunctions. Quickly and accurately locating and promptly eliminating these faults is crucial for ensuring production efficiency and pipe bending quality. The following outlines the causes and troubleshooting approaches for common malfunctions, for reference by on-site technicians.

1. Inaccurate Bending Angle or Excessive Springback

Symptom: The actual bending angle is less than the set value, or the angle fluctuates significantly within the same batch of products.

Possible Causes:

Insufficient springback compensation, especially for materials such as high-strength steel and stainless steel.

The bending angle setting is too small.

Insufficient clamping die pressure, causing pipe slippage.

Encoder or angle sensor signal drift.

Troubleshooting Suggestions:

Increase the bending angle value, testing each piece until the angle stabilizes.

Check if the clamping cylinder pressure reaches the set value, and check for oil contamination on the die working surface.

Calibrate the angle sensor zero point, and check if the coupling is loose.

2. Wrinkling or Collapse at the Bending Point

Symptom: Wavy wrinkles appear on the inner side of the bend, or the cross-section is noticeably flattened or collapsed inward.

Possible Causes:

Anti-wrinkle die not installed or excessive gap between it and the bending die.

Mandrel not used, or insufficient mandrel extension, or ball head misalignment.

Bending radius too small, exceeding the allowable range for the pipe.

Pipe wall thickness too thin or material too soft.

Troubleshooting Suggestions:

Adjust the anti-wrinkle die gap to ensure it fits snugly against the bending die without jamming.

Check mandrel specifications for compatibility; adjust mandrel extension position according to pipe diameter and R-value (usually 0.5-1.5mm before the bending die tangent).

Confirm R/D value is below the process lower limit; increase bending radius or add mandrel support if necessary.

3. Scratches or Indentations on Pipe Surface

Symptoms: Obvious scratches, tears, or die indentations on the pipe surface after bending.

Possible Causes:

Wear, rust, or debris accumulation on the die working surface.

Insufficient lubrication; failure to use specialized bending oil.

Burnt or metal shavings on the pipe surface.

Excessive clamping pressure, causing localized indentations.

Troubleshooting Recommendations:

Inspect and clean all die surfaces in contact with the pipe; grind or replace if necessary.

Apply sufficient bending oil, paying particular attention to the bending die grooves and mandrel area.

Reducing clamping pressure appropriately, ensuring the pipe does not slip.

Clean the pipe blank surface before bending, removing burrs from the ends.

4. Inaccurate feeding length or rotation angle.

Symptoms: Spatial misalignment in multi-bend products, making assembly impossible; length dimensions exceeding tolerance.

Possible Causes:

Feed servo motor or encoder malfunction

Weared linear guide rail, excessive ball screw backlash

Loose rotary shaft coupling, or accumulated mechanical backlash

Incorrect program reference point setting

Troubleshooting Suggestions:

Perform a homing operation and observe whether the feeding and rotary shafts reset accurately.

Check for damage to the guide rail protective cover, clean the guide rail surface and relubricate.

Measure the feeding repeatability with a dial indicator; if out of tolerance, check the screw preload or coupling tightness.

Recheck that the feeding length and rotation angle between each bend in the program match the drawings.

5. Hydraulic System Abnormalities (Noise, Temperature Rise, Slow Action)

Symptoms: Abnormal noise from the hydraulic pump, rapid rise in oil temperature, slow or no cylinder action.

Possible Causes:

Low hydraulic oil level or contaminated/emulsified oil

Clogged suction filter causing pump cavitation

Relief valve set pressure too low or valve core stuck

Radiator fan malfunction or severe dust accumulation on heat sink fins

Troubleshooting Recommendations:

Check oil level; add the same type of hydraulic oil if insufficient.

Observe oil color and condition; replace with new oil and clean the oil tank if severely contaminated or emulsified.

Replace the return and suction filters.

Clean the radiator surface and check if the fan is operating normally.

Measure system pressure with a pressure gauge to confirm if the set value has been reached.

6. Motor Overheat or Overload Alarm

Symptom: Motor casing temperature is too high; control system reports an overload fault.

Possible Causes:

Equipment overload operation; pipe diameter or wall thickness exceeding rated range.

Increased mechanical resistance (wear on reducer, bearings, transmission components).

Low power supply voltage or three-phase imbalance.

Motor fan malfunction or poor ventilation.

Troubleshooting Suggestions:

Confirm that the pipe bending specifications are within the equipment's capacity.

Run the equipment under no-load to determine if there is still a significant load; check the mechanical transmission components.

Measure the power supply voltage and three-phase current; check for any missing phases.

Clean the motor cooling shroud and fan blades to ensure proper ventilation.

7. Control system alarm or touchscreen unresponsive.

Symptoms: HMI black screen, system freeze, or system reports servo/PLC fault.

Possible causes:

Power module failure or blown fuse

Emergency stop button not released or safety circuit disconnected

Servo drive alarm (overvoltage, overcurrent, encoder failure)

Incorrect program parameters or accidental modification

Troubleshooting suggestions:

Check the status of indicator lights on each module in the control cabinet to confirm normal power input

Confirm the emergency stop button is turned out and the safety door switch is closed

Record the drive alarm code and check against the instruction manual

If parameters have been modified, restore the backup program or contact the manufacturer's technical support.

The key to troubleshooting pipe bending machines lies in "observation first, analysis second, and action third." Start with the symptoms, and in conjunction with the equipment's operating status, systematically check each component—electrical, hydraulic, mechanical, and mold-related—avoiding blind disassembly and assembly. Establishing a routine inspection and regular maintenance system can effectively reduce unexpected malfunctions and keep the equipment in optimal working condition at all times.