Servo motor faults and repair methods

Servo motor is a product with a wide range of applications in the motor industry. It is often used in fields that require high-precision positioning, such as machine tools, industrial robotic arms, robots, etc. And the servo motor adopts a closed-loop control structure, which can achieve high accuracy as long as the load is within the rated range. However, during the use of servo motors, some common faults will inevitably occur. So what are the common faults? And how to perform repairs? Let’s take a look below!

Some common faults and repair methods of servo motors are as follows:

1. When the motor is powered on, the machine vibrates (during acceleration/deceleration)

Common causes of such failures in servo motors include:

1. The pulse encoder is faulty. At this time, you should check whether the servo system is stable, whether the circuit board maintenance test current is stable, and whether the voltage on the reaction line terminal of the speed detection unit drops at certain points. If there is a drop, it indicates that the pulse encoder is defective and replace the encoder.

2. The cross coupling of the pulse encoder may be damaged, causing the shaft speed to be out of sync with the detected speed. At this time, the coupling can be replaced.

3. The tachometer generator fails. Measures we can take include: repair and replace the tachometer. During the maintenance practice, the brushes of the tachometer are often worn and jammed. At this time, the brushes of the tachometer should be removed, polished a few times with fine sandpaper, and the dirt on the commutator should be cleaned at the same time, and then reinstalled.

2. When the motor is powered on, the mechanical movement is abnormally fast (speeding)

If this kind of servo motor system failure occurs, you should not only check the position control unit and speed control unit, but also check: ① Whether the pulse encoder wiring is wrong; ② Whether the pulse encoder coupling is damaged; ③ Check whether the tachometer generator terminals are The connection is reversed and the excitation signal line is connected incorrectly. Generally, this kind of phenomenon should be handled by professional circuit board maintenance technicians, otherwise it may cause more serious consequences.

3. The spindle cannot move directionally or the directional movement is not in place.

If this kind of servo system failure occurs, you should check the settings and adjustments of the directional control circuit, check the directional plate, and adjust the spindle control printed circuit board. You should also check whether the output waveform of the position detector (encoder) is normal. To judge the quality of the encoder (it should be noted that the normal output waveform of the encoder should be measured and recorded when the equipment is normal, so that it can be checked in case of failure).

4. The coordinate axis oscillates during feeding

You should check the motor coil, the connection between the mechanical feed screw and the motor, the servo system, the pulse encoder, the coupling, and the tachometer.

5. NC error alarm occurs

NC alarms are caused by program errors and operation errors. For example, the Nc of the FANUC6ME system displays a 090.091 alarm. The reasons may be: ① Main circuit failure and feed speed is too low; ② Pulse encoder is defective; ③ Pulse encoder power supply voltage is too low (at this time, adjust the 15V power supply voltage to make the main The voltage value on the 5V terminal of the circuit board is within 4.95-5.10V); ④ It cannot be executed normally without inputting the one-turn signal of the pulse encoder.

6. Servo system alarm

Servo motor system faults often appear with the following alarm numbers, such as 416, 426, 436, 446, and 456 servo alarms in the FANUC6ME system; 1364 servo alarms in the STEMENS880 system; and 114 and 104 servo alarms in the STEEMENS8 system. At this time, we should check: ① The axis pulse encoder responds to signal disconnection, short circuit or signal loss. Use an indicator to measure the A and B phase one-turn signals to see if they are normal; ② The encoder has an internal fault, causing the signal to be unable to be received correctly, and may also be affected by The influence of factors such as pollution, too much dirt, deformation, etc.