Siemens DC Servo Drive System Maintenance of 10 Cases

example 1. In-line fast fuse blown fault repair

Fault phenomenon: A horizontal machining center supporting SIEMENS 8MC is turned on after the power grid suddenly loses power, and the system cannot start.

Analysis and processing: After inspection, the quick fuse of the X-axis servo drive's incoming line has been blown. The SIEMENS 6RA series DC servo drive is used in the feed system of the machine tool. The servo drive and drive unit are checked against the drive. No component damage and short circuit are found.

Check that the mechanical part of the machine tool is working properly. After replacing the fuse directly, start the machine and resume normal operation. The reason for the analysis is the sporadic failure caused by the sudden power outage of the power grid.

Example 2. Maintenance of SIEMENS 8MC Measurement System Failure

Fault phenomenon: A horizontal machining center supporting SIEMENS 8MC, when the X-axis moves to a certain position, the hydraulic motor is automatically disconnected, and an alarm message appears: the Y-axis measurement system is faulty. After the power is turned off and on again, the machine tool can return to normal operation, but the same fault may occur even if the X axis moves to a certain position.

Analysis and processing: The machine is an imported horizontal machining center supporting SIEMENS 8MC CNC system and SIEMENS 6RA series DC servo drive. Because the Y-axis alarm occurs when the X-axis moves, in order to verify the correctness of the system, the X-axis measurement feedback cable test is dialed and the X-axis measurement system fault alarm occurs. Therefore, the reason for the system's false alarm can be eliminated.

Checking the X-axis at and near the location of the alarm, it is found that it has no interference and influence on the Y-axis measurement system (raster), and only the Y-axis is moved and there is no alarm, and the Y-axis is operating normally. Check the status of the Y-axis motor cable plug, grating read head, and grating scale. No abnormalities were found.

Considering that the equipment is a large-scale machining center with more cables, the cable length between the panel and the machine tool is longer, and all the cables are fixed on the cable rack and the random bed moves back and forth. Based on the above analysis, it is tentatively judged that the possibility of local disconnection is greater due to the bending of the cable.

During the maintenance, the X axis was intentionally moved to the point where the fault occurred. The cable was manually moved and the connection of each feedback signal line on the Y axis was carefully measured. Eventually, it was found that one of the signal lines appeared occasionally during the cable movement. Open circuit phenomenon; after replacing the broken line with the backup line in the cable, the machine tool returns to normal.

Example 3 ~ Example 4. Drive fault caused by following error error alarm repair

Symptom: The CNC gear hobbing machine of a supporting SIEMENS PRIMOS system and 6RA26** series DC servo drive system moves the Z axis of the machine after starting up, and the system generates an "ERR22 following error over tolerance" alarm.

Analysis and processing process: CNC machine tool following error exceeds the alarm, the essence of which is the actual machine tool can not reach the command position. The cause of this fault is usually a failure of the servo system or a failure of the machine's mechanical transmission system.

Since the servo feed system of the machine tool is a fully closed loop structure, it cannot be tested by disconnecting the motor from the mechanical part. In order to confirm the fault location, first of all, when the machine is powered off and the clamping mechanism is released, the Z-axis screw is manually turned and no abnormality in the mechanical transmission system is found. The initial judgment is that the fault is caused by a bad servo system or numerical control device. .

In order to further determine the fault location, when the system is turned on during maintenance, use the handwheel to move the Z-axis a little (the moving distance should be controlled within the maximum allowable following error set by the system to prevent the following error alarm from occurring) and measure the Z-axis direct current. The speed of the driver is given by the voltage. After inspection, it is found that there is a voltage input given by the speed, and the magnitude of the value is related to the distance and direction of the hand wheel movement. From this, it can be confirmed that the numerical control device is operating normally, and the fault is caused by a bad servo driver.

Check the drive and found that the status indicator of the drive itself has no alarm, basically it can eliminate the fault of the main circuit of the drive. Considering that the X and Z axis drive models of the machine tool are the same, the fault location is confirmed on the A2 board of the 6RA26** DC drive by switching the drive control boards one by one.

According to the schematic diagram of the SIEMENS 6RA26** series of DC servo drives, check and measure all levels of signals one by one, and finally confirm that the cause of the fault is caused by a defect in the integrated voltage comparator N7 (model: LM348) on the A2 board: after the replacement, the machine tool is recovered. normal.

Example 4.

Symptom: An imported horizontal machining center supporting the SIEMENS 850 system and 6RA26** series DC servo drive system. After starting the machine, the X axis is manually moved. The X axis table of the machine tool does not move. The CNC displays an X following error error alarm. .

Analysis and processing: As the other axes of the machine work normally, the X-axis driver has no alarm and all status indicators indicate no fault. To determine the fault location, consider the same speed/current regulation board A2 of the 6RA26** series of DC servo drives. The A2 board of the X-axis driver and the A2 board of the Y-axis driver were tested for alignment during maintenance. Through tests, it has been found that the X axis can work normally, but the Y axis appears to follow the out-of-tolerance alarm.

Based on this phenomenon, it can be concluded that the X-axis driver has a poor speed/current regulator board. According to SIEMENS 6RA26** series DC servo driver schematic diagram, the measurement inspection found that when a small amount of movement of the X-axis when the drive speed given input between the 57 and 69 terminals have analog input, measuring drive detection terminal B1, speed analog voltage is correct However, the 6-pin output of the speed proportional regulator N4 (LM301) is always 0V.

Check the schematic diagram one by one to check the feedback resistor R25, R27, R21 of the speed regulator LM301, the offset adjustment resistors R10, R12, R13, R15, R14, R12, and the input protection diodes V1, V2 of the LM301, given the filter link R1, C1, R20, V14, R27, R28, R8, R3, C5, R4, and other peripheral components of the speed feedback filter component, all components are confirmed to be fault-free.

Therefore, the cause of the failure is caused by the poor integration of the LM301 amplifier. After the LM301 is replaced, the machine tool resumes normal operation and the fault is rectified.

Example 5. CNC fault caused by following error error alarm repair

Analysis and processing process: The fault analysis process is the same as the previous example. However, in this example, when using the handwheel to move the Z-axis a little, measuring the speed given voltage of the Z-axis DC drive is always 0, so the fault can be initially determined in the numerical control device or numerical control Connect the cable with the drive.

Check that the cable connection between the CNC device and the driver is normal and confirm that the cause of the fault is in the CNC device. Turn on the digital device check and find that the digital output of the Z-axis speed given output D/A converter is correct, but there is no analog output, thus confirming that the fault is caused by a bad D/A converter.

After replacing the Z-axis speed given output 12-bit D/A converter DAC0800, machine tool recovery

Example 6.

Symptoms: A CNC gear hobbing machine supporting a SIEMENS PRIMOS system and a 6RA26** series DC servo drive system generates an "ERR21, Y axis measurement system error" alarm after startup.

Analysis and processing: The reasons for the occurrence of measurement system alarms in the CNC system are generally as follows:

1) The position feedback signal interface circuit of the numerical control device is defective.

2) Defective connection cable between numerical control device and position detection component.

3) Poor position measurement system itself.

Since the machine tool servo drive system uses a full closed loop structure, the detection system uses a grating from HEIDENHAIN. In order to determine the fault location, the speed of the X and Y axes output from the numerical control device is first given during the maintenance, and the drive enable and the position feedback of the X and Y axes are adjusted so that the X axis output of the numerical control controls the Y axis and the Y axis output. Control the X axis. After the alignment, the CNC system was operated, the Y-axis was manually moved, and the X-axis of the machine tool was moved, and the operation was normal. It was proved that the position feedback signal interface circuit of the NC device was not faulty.

However, when operating the CNC system and manually moving the X-axis, the Y-axis of the machine tool will not move, and at the same time, the CNC displays the â€œERR21, X-axis measurement system errorâ€ alarm. This confirms that the alarm was caused by a fault in the position measurement system and is independent of the interface circuit of the numerical control device. Check that the measuring system cable is connected correctly and reliably, eliminating the problem of cable connection.

Using an oscilloscope to check the Ual, Ua2, *Ua1, and Ua2 output waveforms of the pre-amplifier EXE601/5-F of the position measurement system, it was found that the Ua1 phase has no output. Further inspection of the raster output (preamplifier EXE601/5-F input) signal waveforms reveals that Ie1 has no signal input. Check that the machine tool grating is installed correctly and that the malfunction is caused by a defective grating: After replacing the grating LS903, the machine tool returns to normal operation.

Example 7.

Symptoms: A CNC gear hobbing machine with a SIEMENS PRIMOS system and a 6RA26** series DC servo drive system is used. When the power is turned on, an "ERR21, X axis measurement system error" alarm occurs.

Analysis and Processing: The fault analysis process is the same as the previous example. However, in this example, the Ual and Ua2, *Ual, and *Ua2 output waveforms of the pre-amplifier EXE601/5-F of the position measurement system were examined using an oscilloscope, and it was found that the same Ual has no output. . Further check the signal waveform of the raster output (pre-amplifier EXE601/5-F input), found that Ie1, the signal input is correct, confirm that the fault is caused by the poor pre-amplifier EXE601/5-F.

According to the principle of EXE601/5-F (details will be described later), the signal of the preamplifier EXE601/5-F is measured step-by-step, and one of the LM339 integrated voltage comparators is found to be defective; after the replacement, the machine tool resumes normal operation.

Example 8. Drive is not ready for fault repair

Fault phenomenon: A horizontal machining center supporting the SIEMENS 850 system and 6RA26** series DC servo drive system suddenly stops during processing. The â€œdrive failureâ€ indicator on the rear panel of the engine is on, and the machine tool cannot start normally.

Analysis and processing: According to the phenomenon of "drive fault" indicator light on the panel, combined with the machine electrical diagram and the system PLC program analysis, to confirm the cause of the machine is the Y-axis driver is not ready.

Check the driver in the cabinet and measure the power input of the main circuit of the 6RA26** driver. Only the V phase has voltage. Further check according to the electrical diagram of the machine tool and find that the U and W phases of the 6RA26** driver's incoming fuse are blown. Use a multimeter to measure the 1U, 1W of the main circuit input terminal of the driver and confirm that there is a short circuit in the main circuit of the driver.

Since the main circuit of the 6RA26** AC drive is directly connected to the thyristor, it can be confirmed that the fault is caused by damage to the thyristor.

Measure the main circuit thyristors V1-V6 one by one, and confirm that V1 and V2 are defective (short-circuited); after replacing spare parts of the same specifications, the machine tool returns to normal.

Since the rest of the drive is not faulty, the thyristor module is replaced and the machine tool resumes normal operation. The analysis may be due to an accidental fault caused by transient voltage fluctuations or load fluctuations.

Example 9. Faults caused by external faults causing the motor not to turn

Fault phenomenon: An imported vertical machining center supporting the SIEMENS 6M system found that the tool magazine could not rotate normally during tool change.

Analysis and processing: Through the analysis of the electrical diagram of the machine tool, the rotary control of the tool magazine adopts the 6RA** series of DC servo drives, and the tool magazine speed is made by the machine tool manufacturer. â€œMagazine conversion setting/positioning control "The board is controlled.

The on-site analysis and observation of rotary motion of the tool magazine revealed that when the tool magazine was rotated, the PLC rotation signal was input, and the tool magazine mechanical bolt was pulled out, but the 6RA26** driver's conversion given analog quantity was not input. Since the output of this analog quantity comes from the â€œknife library setpoint conversion/positioning controlâ€ board, the â€œknife library setpoint conversion/positioning controlâ€ board schematic diagram provided by the machine tool manufacturer is measured step by step and finally found on the board. The analog switch (model DG201) is damaged. After replacing the spare parts of the same model, the machine tool resumes normal operation.

Example 10. Start-up motor is high-speed rotation fault repair

Symptom: A machine with the same model as Example 268 has a tool magazine that rotates at a high speed after the manual press of the tool magazine rotation button during the startup, causing the machine to alarm.

Analysis and processing: According to the fault phenomenon, it can be initially determined that the fault is due to the negative polarity feedback of the magazine DC drive speed measurement or the speed loop positive feedback or open loop caused by the speed feedback line coming off. The measurement confirms that the servo motor speed feedback line is connected, but the polarity is incorrect; after exchange of speed feedback feedback polarity, the magazine operation returns to normal.

2. Schneider servo drive common fault analysis and solution

1. How to deal with servo motor when there is pulse output?

1 Monitor the controller's pulse output current value and whether the pulse output lamp is flashing, confirm that the command pulse has been executed and has normally output the pulse;

2 Check whether the control cable, power cable and encoder cable of the controller to the driver are wrongly wired, damaged or have bad contact;

3 Check if the brake of the servo motor with brake is turned on;

4 monitor the servo driver panel to confirm whether the pulse command is input;

5 Run command is normal;

6 control mode must choose position control mode;

7 The servo driver setting input pulse type and command pulse settings are the same;

8 Ensure that the forward rotation side drive prohibition, reverse side rotation prohibition signal, and deviation counter reset signal are not input, disconnect the load, and the no-load operation is normal. Check the mechanical system.

2. How to deal with the motor deviation counter overflow error when the servo motor rotates at high speed?

1 motor deviation counter overflow error occurred during high speed rotation;

Countermeasures:

Check if the wiring of the motor power cable and encoder cable is correct and if the cable is damaged.

2 Motor deviation counter overflow error occurs when a long command pulse is input.

Countermeasures:

a. The gain setting is too large, manually adjust the gain again or use the automatic adjustment gain function;

b. Increase the acceleration and deceleration time;

c. If the load is too heavy, it is necessary to re-select a larger capacity motor or reduce the load, and add a gearbox and other transmission mechanisms to increase the load capacity.

3 Motor deviation counter overflow error occurred during operation.

Countermeasures:

a. Increase the deviation counter overflow setting;

b. Slow down the rotation speed;

c. increase the acceleration and deceleration time;

d. If the load is too heavy, you need to re-select a larger capacity motor or reduce the load. Add a gearbox and other gear mechanisms to increase the load capacity.

3, servo motor is not overloaded with a load, how to deal with?

1 Occurs if the servo Run signal is on and is not pulsed:

a. Check the servo motor power cable wiring and check for any poor contact or broken cable.

b. If it is a servo motor with brake, be sure to open the brake;

c. Is the speed loop gain too large?

d. The speed loop integral time constant is set too small.

2 If the servo just happens during operation:

a. Is the position loop gain too large?

b. Is the positioning amplitude set too small?

c. Check that there is no stall on the servo motor shaft and readjust the machine.

4. When the servo motor runs abnormal noise or jitter, how to deal with it?

1 Servo wiring:

a. Use standard power cables, encoder cables, control cables, and cables for damage;

b. Check whether there is interference source near the control line, and whether it is parallel or close to the high current power cable nearby;

c. Check if there is any change in the potential of the ground terminal. Ensure that the grounding is good.

2 Servo parameters:

a. The servo gain setting is too large. It is recommended to re-adjust the servo parameters manually or automatically.

b. Confirm the speed feedback filter time constant setting, the initial value is 0, you can try to increase the setting value;

c. Electronic gear ratio is set too large, it is recommended to restore to factory settings;

d. The resonance of the servo system and the mechanical system, try to adjust the notch filter frequency and amplitude.

3 Mechanical System:

a. The coupling coupling between the motor shaft and the equipment system is offset and the mounting screws are not tightened;

b. Poor engagement of pulleys or gears will also cause changes in the load torque, try to run without load, if the normal operation of the no-load, then check whether there is abnormality in the combined part of the mechanical system;

c. Check if the load inertia, torque and speed are too large. Try to run without load. If the no-load operation is normal, reduce the load or replace the larger drive and motor.

5, Schneider servo motor position control positioning is not accurate, how to deal with?

1 First, confirm whether the current value of the actual pulse sent by the controller is consistent with the expected value. If not, check and correct the program.

2 Monitor whether the number of pulse instructions received by the servo driver is the same as that issued by the controller. If not, check the control cable.

III. Panasonic Servo Driver Maintenance Common Problems and Solutions

1, Panasonic digital AC servo system MHMA 2KW, when the test machine is powered on, the motor vibrates and there is a lot of noise, then the driver appears No. 16 alarm, how to solve?

This phenomenon is generally due to the driver's gain setting is too high, resulting in self-oscillation. Please adjust parameter No.10, No.11 and No.12 to reduce the system gain appropriately. (Refer to the "Instruction Manual" for gain adjustment)

2. When Panasonic AC servo driver is powered up, it will display 22nd alarm. Why?

No. 22 alarm is an encoder fault alarm. The reasons for this are:

A. There is a problem with the encoder wiring: disconnection, short circuit, wrong connection, etc. Please check carefully;

B. There is a problem with the encoder on the motor: Displacement, damage, etc. Please send it to us.

3, Panasonic servo motor running at a very low speed, when fast, slow, like crawling, how to do?

The low-speed crawling phenomenon of the servo motor is generally caused by the low system gain. Please adjust parameters No.10, No.11 and No.12, adjust the system gain appropriately, or run the automatic gain adjustment function of the driver. (Refer to the "Instruction Manual" for gain adjustment)

4. Panasonic AC servo system In the position control mode, the control system outputs the pulse and direction signals. However, regardless of the forward or reverse command, the motor only turns in one direction. Why?

Panasonic AC servo system can receive three kinds of control signals in the position control mode: pulse/direction, forward/backward pulse, A/B orthogonal pulse. The factory setting of the driver is A/B quadrature pulses (No 42 is 0). Change No. 42 to 3 (pulse/direction signal).

5. In the use of Panasonic AC servo system, can I use Servo-ON as the signal to control the motor offline to directly rotate the motor shaft?

Although the motor can be taken offline (in a free state) when the SRV-ON signal is turned off, do not use it to start or stop the motor. Frequent use of it to switch the motor may damage the drive. If you need to implement the offline function, you can use control mode switching to achieve: Assuming the servo system requires position control, you can set the control mode selection parameter No02 to 4, that is, the first mode is position control, and the second mode is torque control. . Then use C-MODE to switch the control mode: In the position control, the signal C-MODE is turned on so that the driver works in the first mode (ie, position control); when the need to go offline, the signal C-MODE is closed, When the driver is operated in the second mode (ie, torque control), since the torque command input TRQR is not connected, the motor output torque is zero, thereby achieving offline.

6. The Panasonic AC servo used in the CNC milling machine we developed works in the analog control mode. The position signal is fed back to the computer by the pulse output of the driver. After the machine is installed and debugged, the movement instruction is issued and the motor runs on the fly. What are the reasons?

This phenomenon is caused by the wrong phase sequence of the A/B quadrature signal fed back to the computer by the driver pulse output and the formation of positive feedback. The following methods can be used to handle this phenomenon:

A. Modify the sampling program or algorithm;

B. Reverse the A+ and A- (or B+ and B-) pulse output signals of the driver to change the phase sequence;

C. Modify the driver parameter No.45 to change the phase sequence of its pulse output signal.

7. In a testing device developed by us, Panasonic AC servo system was found to have some interference with our detection device. What should be done to eliminate it?

Because the AC servo driver adopts the principle of the inverter, it is a prominent source of interference in the control and detection system. In order to reduce or eliminate the interference of the servo driver to other electronic devices, generally the following methods can be used:

A. The ground of the driver and motor should be reliably grounded;

B. The driver's power input plus isolation transformer and filter;

C. Use shielded cables for all control signals and detection signal lines.

The problem of interference is a very difficult problem in the electronic technology. There is no fixed method to eliminate it completely and effectively. Anti-jamming measures are usually found through experience and experimentation.

8, why the servo motor will not lose step?

The servo motor driver receives the feedback signal from the motor encoder and compares it with the command pulse to form a semi-closed-loop control of the position. Therefore, the servo motor will not lose step, and each command pulse can be reliably responded.

9, how to consider Panasonic servo power supply problem?

At present, almost all Japanese-made AC servo motors are three-phase 200V power supply, the domestic power supply standard is different, so it must be resolved as follows:

A. For AC servos up to 750W, the single-phase 220V can be directly connected to the L1 and L3 terminals of the driver.

B. For other types of motors, it is recommended to use a three-phase transformer to convert three-phase 380V to three-phase 200V to access the L1, L2, L3 of the drive.

10. What should you pay special attention to when installing the servo motor mechanically?

Since each servo motor is equipped with a rotary encoder at the rear end, it is a very delicate and delicate optical device. Excessive impact force will certainly damage it.

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