How to Repair a Faulty Sensor in a Pipe Bending Machine?

Sensors are the "nerve endings" of a pipe bending machine, responsible for monitoring key parameters such as bending angle, mandrel position, clamping status, and feed stroke. If a sensor fails, the equipment may experience angle deviation, abnormal operation, or alarm shutdown. Mastering sensor fault diagnosis and repair methods is an important skill for ensuring the normal operation of the equipment.

Common Sensor Types and Fault Symptoms

Common sensors used in pipe bending machines include:

Angle Sensor/Encoder: Monitors the rotation angle of the bending arm. Fault symptoms: Large bending angle deviation, abnormal springback, angle display fluctuations, or no signal.

Proximity Switch: Detects position signals such as mandrel advance/retreat, clamping position, and feed origin. Fault symptoms: No response, false triggering, intermittent signal.

Displacement Sensor: Measures cylinder stroke or feed length. Fault symptoms: Inaccurate dimensions, signal fluctuations, and fluctuating displayed values.

Troubleshooting and Repair Steps

Step 1: Power Off and Safety Confirmation

Before performing any sensor maintenance, always turn off the main power supply to the equipment and release the hydraulic system pressure to prevent accidental operation and injury.

Step 2: Visual Inspection

Inspect the sensor for cracks, deformation, or oil contamination. Check for loose or oxidized terminals, and for worn or broken cable sheaths. Check the sensing surface for dust or metal debris—a common cause of proximity switch failure.

Step 3: Electrical Parameter Testing

Use a multimeter to perform three key tests: check if the power supply voltage is within the rated range (e.g., DC12-24V or AC90-250V); check if the output signal voltage is normal; check if the load current exceeds the rated value. For encoders, use an oscilloscope to observe whether the output waveform is stable and if the amplitude meets requirements.

Step 4: Signal and Interference Troubleshooting

Confirm that the sensor installation position is secure and that the sensing distance to the object being measured is appropriate. Check for strong electromagnetic interference sources in the vicinity (e.g., frequency converters, high-power motors). If necessary, add shielding to the signal line and ground it at one end.

Step 5: Calibration and Parameter Check

If the angular deviation is large, the sensor zero point needs to be recalibrated. Check if the sensor parameter settings in the control system are correct, such as the measurement range and communication protocol. For encoders, also check if the connection key is dislodged from the keyway and if the photoelectric components are dirty.

Step 6: Replace the Faulty Sensor

If the above steps do not solve the problem, it indicates that the internal components of the sensor are damaged and a sensor of the same model needs to be replaced. When replacing, ensure the power is off, connect the wires correctly, recalibrate the parameters after replacement, and perform a test run to verify.

Preventative Maintenance Recommendations

Clean the sensor sensing surface regularly to prevent oil and dust from affecting detection sensitivity.

Calibrate the sensor every six months to ensure measurement accuracy.

Maintain a spare sensor inventory; it is recommended to have spare parts for sensors in critical locations.

Select sensors with higher protection ratings (e.g., IP67 or higher) for harsh environments.

Pay attention to the sensor's operating temperature range to avoid exceeding the rated value, which can lead to performance degradation.

Although small, sensors directly affect pipe bending accuracy and equipment safety. Mastering standardized diagnostic and repair procedures can quickly locate problems and reduce downtime.