1. What needs to be done before starting the servo motor?

 

1. Measure the insulation resistance (for low-voltage motors, it should not be lower than 0.5M).

 

2. Measure the power supply voltage, check whether the motor wiring is correct and whether the power supply voltage meets the requirements.

 

3. Check whether the starting equipment is in good condition.

 

4. Check whether the fuse is suitable.

 

5. Check whether the motor grounding and zero connection are good.

 

6. Check whether the transmission device is defective.

 

7. Check whether the motor environment is suitable, and remove flammable materials and other debris.

 

 

 

2. What are the reasons for the overheating of the servo motor bearings?

 

The motor itself:

 

1. The inner and outer rings of the bearing are too tightly matched.

 

2. There is a problem with the shape and position tolerance of the parts, such as the coaxiality of the machine base, end cover, shaft and other parts.

 

3. Improper selection of bearings.

 

4. The bearing is poorly lubricated or the bearing is not cleaned, and there is debris in the grease.

 

5. Shaft current.

 

Use aspect:

 

1. Improper installation of the unit, such as the coaxiality of the motor shaft and the driven device.

 

2. Pulling the pulley is too tight.

 

3. The bearing is not well maintained, the lubricating grease is insufficient or exceeds the service life, and it becomes dry and deteriorated.

 

 

 

 

3. What is the reason for the unbalanced three-phase current of the servo motor?

 

1. The three-phase voltage is unbalanced.

 

2. Poor welding or poor contact of a phase branch circuit inside the motor.

 

3. Short circuit between motor winding turns or phase to ground.

 

4. Wiring error.

 

 

4. How to control the speed of the servo motor?

 

The servo motor is a typical closed-loop feedback system. The reduction gear set is driven by the motor, and its terminal (output end) drives a linear proportional potentiometer for position detection. The potentiometer converts the corner coordinates into a proportional voltage and feeds it back to the control circuit board. The control circuit board compares it with the input control pulse signal, generates a correction pulse, and drives the motor to rotate in a forward or reverse direction, so that the output position of the gear set matches the expected value, and the correction pulse tends to 0, so as to achieve the servo The purpose of precise positioning and constant speed of the motor.

 

 

 

 

5. Observe whether sparks are generated between the carbon brush and the commutator when the motor is running and the degree of sparks to repair

 

1. There are only 2 to 4 tiny sparks. If the surface of the commutator is flat at this time. In most cases, repair is not necessary;

 

2. There is no spark. No need to repair;

 

3. There are more than 4 very small sparks, and there are 1 to 3 large sparks, you don't need to disassemble the armature, just use sandpaper to grind the carbon brush commutator;

 

4. If there are more than 4 large sparks, the commutator needs to be ground with sandpaper, and the carbon brush and armature must be removed. Replace the carbon brush and polish the carbon brush.

 

 

 

6. Repair of commutator

 

1. The surface of the commutator is obviously uneven (touch by hand) or sparks when the motor is running, as in the fourth case. At this time, the armature needs to be disassembled and the converter is processed with a precision machine tool;

 

2. Basically flat, but with very small scars or sparks. For example, in the second case, l port 1 is hand-grinded with water and sandpaper without disassembling the armature. The order of grinding is: first process a wooden tool according to the arc of the commutator, cut water sandpaper of several different thicknesses into strips as wide as the commutator, and remove the carbon brush (please note Mark the handle of the removed carbon brush and the carbon brush slot to ensure that the left and right are not changed during installation) Use a wooden tool wrapped with sandpaper to fix the commutator, and press the motor rotation direction with the other hand. Lightly rotate the shaft commutator to grind. Servo motor repairs use the order of the thickness of sandpaper to be coarser then finer. When a piece of sandpaper is too sandy to be used, change another finer sandpaper until the finest water sandpaper (or metallographic sandpaper) is used up.

 

 

Seven, how to align the servo motor encoder phase and rotor magnetic pole phase zero point repair

 

1. Phase alignment of incremental encoder

 

The alignment method between the phase of the UVW electronic commutation signal of the incremental encoder with commutation signal and the phase of the rotor magnetic pole, or the electrical angle phase, is as follows:

 

1) Use a DC power supply to pass a DC current smaller than the rated current to the UV winding of the motor, U input, V output, and orient the motor shaft to a balanced position;

 

2) Observe the U-phase signal and Z signal of the encoder with an oscilloscope;

 

3) Adjust the relative position of the encoder shaft and the motor shaft;

 

4) While adjusting, observe the encoder's U-phase signal transition edge and Z signal until the Z signal is stable at a high level (here the normal state of the Z signal is low by default), lock the encoder and the motor relative Positional relationship;

 

5) Twist the motor shaft back and forth, after letting go, if the Z signal can be stabilized at a high level every time the motor shaft freely returns to the equilibrium position, the alignment is valid.

 

2. Phase alignment of absolute encoder

 

The phase alignment of the absolute encoder is not much different for single-turn and multi-turn. In fact, the phase alignment of the encoder is aligned with the phase of the electrical angle of the motor within one turn. At present, a very practical method is to use the EEPROM inside the encoder to store the measured phase after the encoder is randomly installed on the motor shaft. The specific method is as follows:

 

1) Install the encoder on the motor randomly, that is, consolidate the encoder shaft and motor shaft, as well as the encoder housing and motor housing;

 

2) Use a DC power supply to pass a DC current less than the rated current to the UV winding of the motor, U input, V output, and orient the motor shaft to a balanced position;

 

3) Use the servo drive to read the single-turn position value of the absolute encoder and store it in the EEPROM that records the initial phase of the electrical angle of the motor inside the encoder;

 

4) The alignment process ends.

 

 

 

8. Servo motor maintenance movement phenomenon

 

The movement phenomenon occurs during the feed, and the speed measurement signal is unstable, such as a crack in the encoder; poor contact of the terminal, such as a loose screw, etc.; when the movement occurs at the moment of reversing from the positive direction to the reverse direction, the general It is caused by the backlash of the feed transmission chain or the servo drive gain is too large.

 

Nine, servo motor maintenance crawling phenomenon

 

It mostly occurs in the start acceleration section or low-speed feed. It is generally caused by factors such as poor lubrication of the feed transmission chain, low servo system gain and excessive external load. In particular, it should be noted that the coupling used to connect the servo motor and the ball screw, due to the loose connection or the defect of the coupling itself, such as cracks, causes the ball screw and the servo motor to rotate out of synchronization, which makes the feed Movement is fast and slow.

 

10. Servo motor maintenance vibration phenomenon

 

When the machine tool is running at high speed, vibration may occur, and an overcurrent alarm will be generated at this time. Machine vibration problems are generally speed problems, so the speed loop problem should be looked for.

 

11. Servo motor maintenance torque reduction phenomenon

 

When the servo motor is running from the rated locked-rotor torque to high-speed operation, it is found that the torque will suddenly decrease. This is caused by the heat dissipation of the motor winding and the heat of the mechanical part. At high speeds, the temperature rise of the motor becomes larger. Therefore, the load of the motor must be checked before using the servo motor correctly.

 

12. Servo motor maintenance position error phenomenon

 

When the servo axis movement exceeds the position tolerance range (KNDSD100 factory standard setting PA17: 400, position out of tolerance detection range), the servo drive will appear "4" position out of tolerance alarm.

 

The main reasons are:

 

The tolerance range of the system setting is small; the servo system gain is set improperly; the position detection device is polluted; the cumulative error of the feed transmission chain is too large, etc.

 

13. Servo motor maintenance does not rotate

 

In addition to connecting the pulse + direction signal from the CNC system to the servo drive, there is also an enable control signal, which is generally DC+24V relay coil voltage.

 

Servo motor does not rotate, common diagnostic methods are:

 

1. Check whether the CNC system has pulse signal output;

 

2. Check whether the enable signal is turned on; observe whether the input/output status of the system meets the starting conditions of the feed axis through the LCD screen;

 

3. Confirm that the brake has been opened for the servo motor with electromagnetic brake; the drive is faulty; the servo motor is faulty;

 

4. The coupling of the servo motor and the ball screw fails or the key is disconnected, etc.