Common problems and solutions of Siemens, Schneider and Panasonic servo drive maintenance
1. Ten cases of fault repair of Siemens DC servo drive systemexample 1. Fault repair of incoming line fuse fuse fault phenomenon: a horizontal machining center equipped with SIEMENS 8MC is turned on after the power grid is suddenly cut off, and the system cannot be started.
Analysis and processing process: After inspection, the incoming fast fuse of the X-axis servo drive of the machine tool has been fused. The feed system of this machine tool is the SIEMENS 6RA series DC servo drive. The servo motor and drive device are checked against the drive, and no damage or short circuit of any components is found.
Check that the mechanical part of the machine tool is also working properly. After directly replacing the fuse, start the machine tool and resume normal work. The reason for the analysis is the accidental failure caused by the sudden power failure of the power grid.
Example 2. Maintenance failure phenomenon of SIEMENS 8MC measurement system failure:A horizontal machining center equipped with SIEMENS 8MC, when the X axis moves to a certain position, the hydraulic motor is automatically disconnected, and an alarm prompt appears: the Y axis measurement system is faulty. When the power is turned off and then on again, the machine tool can resume normal operation, but the same failure may occur when the X axis moves to a certain position.
Analysis and processing process: The machine tool is an imported horizontal machining center, equipped with SIEMENS 8MC numerical control system, and SIEMENS 6RA series DC servo drive. Since the Y-axis alarm appears when the X-axis moves, in order to verify the correctness of the system, the X-axis measurement feedback cable test was pulled out, and the system has an X-axis measurement system failure alarm. Therefore, the cause of the system false alarm can be eliminated.
Check that the X-axis is at and near the location where the alarm occurred and found that it has no interference or influence on the Y-axis measurement system (grating), and there is no alarm when only the Y-axis is moved. The Y-axis works normally. Then check the condition of the Y-axis motor cable plug, the grating reading head and the grating ruler, and no abnormality is found.
Considering that the equipment belongs to a large machining center, there are many cables, the length of the cable between the electric cabinet and the machine tool is long, and all the cables are fixed on the cable rack, and the bed moves back and forth at random. Based on the above analysis, it is preliminarily judged that there is a high possibility of partial disconnection due to the bending of the cable.
During maintenance, the X axis is intentionally moved to the location of the fault point, the cable is artificially moved, and the connection of each feedback signal line on the Y axis is carefully measured. Finally, one of the signal lines appears occasionally during the continuous movement of the cable. Open circuit phenomenon; after replacing the broken wire with the spare wire in the cable, the machine tool returns to normal.
Example 3 ~ Example 4.Drive failure caused the following error out-of-tolerance alarm maintenance failure phenomenon: a CNC hobbing machine equipped with SIEMENS PRIMOS system and 6RA26 ** series DC servo drive system moved the Z axis of the machine tool after startup, and the system generated an "ERR22 following error out-of-tolerance" alarm.
Analysis and processing process: The follow-up error of CNC machine tool exceeds the alarm, the essence is that the actual machine tool cannot reach the commanded position. The cause of this failure is usually the failure of the servo system or the failure of the machine tool mechanical transmission system.
Because the machine tool servo feed system is a fully closed loop structure, it is impossible to test by disconnecting the connection between the motor and the mechanical part. In order to confirm the fault location, the Z axis screw was manually turned when the machine was powered off and the clamping mechanism was loosened during maintenance. No abnormality was found in the mechanical transmission system. It was initially determined that the fault was caused by a bad servo system or CNC 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 small amount (the moving distance should be controlled within the maximum allowable following error set by the system to prevent the following error alarm), and measure the Z axis The speed of the drive is given a voltage. After inspection, it is found that the speed is given a voltage input, and its value is related to the distance and direction of the handwheel movement. From this, it can be confirmed that the numerical control device is working normally, and the failure is caused by the failure of the servo driver.
Check the drive and find that there is no alarm in the status indicator of the drive itself, which can basically eliminate the failure of the main circuit of the drive. Considering that the X and Z axis drivers of the machine tool are of the same type, confirm the fault location on the A2 board of the 6RA26 ** DC driver by exchanging the control boards of the drivers one by one.
According to the schematic diagram of the SIEMENS 6RA26 ** series DC servo drive, check and measure the signals at all levels one by one, and finally confirm that the cause of the failure is due to the failure of the integrated voltage comparator N7 (model: LM348) on the A2 board: After replacement, the machine tool is restored normal.
Example 4.Fault phenomenon: An imported horizontal machining center equipped with SIEMENS 850 system and 6RA26 ** series DC servo drive system. After starting, manually move the X axis, the machine tool X axis table does not move, and the CNC follows the X following error alarm. .
Analysis and processing process: Since the other coordinate axes of the machine tool work normally, the X-axis drive has no alarm, and all status indicators indicate no failure. In order to determine the fault location, considering the speed / current adjustment board A2 of the 6RA26 ** series DC servo drive, During maintenance, the A2 board of the X-axis driver and the A2 board of the Y-axis driver were swapped and tested. The experiment found that the X axis can work normally, but the Y axis follows the out of tolerance alarm.
According to this phenomenon, it can be concluded that the speed / current regulator board of the X-axis driver is defective. According to the schematic diagram of the SIEMENS 6RA26 ** series DC servo driver, the measurement and inspection found that when a small amount of X axis is moved, there is an analog input between the 57 and 69 terminals of the speed reference input of the driver, and the detection terminal B1 of the driver is measured. The speed analog voltage is correct , But the 6-pin output of speed proportional regulator N4 (LM301) is always 0V.
Check the feedback resistors R25, R27, R21 of the speed regulator LM301, offset adjustment resistors R10, R12, R13, R15, R14, R12, and the input protection diodes V1, V2 of LM301, given the filter link R1 C1, R20, V14, R27, R28, R8, R3, C5, R4 and other peripheral components in the speed feedback filter, confirm that all components are free of faults.
Therefore, it is confirmed that the cause of the failure is due to the poor integration of the LM301 integrated op amp; after replacing the LM301, the machine tool resumes normal operation and the failure is eliminated.
Example 5. CNC fault caused by following error out of tolerance alarm maintenanceFault phenomenon: A CNC hobbing machine equipped with SIEMENS PRIMOS system and 6RA26 ** series DC servo drive system moves the Z axis of the machine tool after startup, and the system generates an "ERR22 following error out of tolerance" alarm.
Analysis and processing process: The fault analysis process is the same as the previous example, but in this example, when the Z axis is moved by a small amount of handwheel, the speed given voltage of the Z-axis DC drive is always 0, so it can be preliminarily determined that the fault is in the CNC device or CNC On the connecting cable with the drive.
Check that the cable connection between the CNC device and the drive is normal, and confirm that the cause of the fault is in the CNC device. Turn on the numerical control device to check and find that the digital input of the speed given output D / A converter of the Z axis is correct, but there is no analog output, thus confirming that the failure is caused by the defective D / A converter.
After replacing the 12-bit D / A converter DAC0800 of the speed reference output of the Z axis, the machine tool recovers
Example 6. Failure phenomenon:A CNC hobbing machine equipped with a SIEMENS PRIMOS system and a 6RA26 ** series DC servo drive system generates an "ERR21, Y-axis measurement system error" alarm after it is turned on.
Analysis and processing process: The reasons for the alarm of the measurement system of the CNC system are generally as follows:
1) The position feedback signal interface circuit of the numerical control device is bad.
2) The connection cable between the numerical control device and the position detection components is defective.
3) The position measurement system itself is defective.
Because the servo drive system of this machine tool adopts a full closed loop structure, the detection system uses the grating of HEIDENHAIN company. In order to determine the fault location, the X and Y axis speeds output by the numerical control device are first given during maintenance, the drive enable and the position feedback of the X and Y axes are adjusted, and the X axis output of the numerical control is controlled by the Y axis and the Y axis output Control the X axis. After the adjustment, the CNC system was operated, the Y axis was moved manually, and the X axis of the machine tool moved, and it was working normally, proving that the position feedback signal interface circuit of the CNC device was fault-free.
However, the CNC system is operated, the X axis is moved manually, and the Y axis of the machine tool does not move. At the same time, the CNC displays "ERR21, X axis measurement system error" alarm. It was confirmed from this that the alarm was caused by a bad position measurement system and had nothing to do with the interface circuit of the numerical control device. Check that the cable connection of the measurement system is correct and reliable, eliminating the problem of cable connection.
Use the oscilloscope to check the Ual and Ua2, * Ua1 and Ua2 output waveforms of the preamplifier EXE601 / 5-F of the position measurement system, and find that there is no output of Ua1 phase. Further inspection of the raster output (preamplifier EXE601 / 5-F input) signal waveform, Ie1 found no signal input. Check that the machine tool grating is installed correctly and confirm that the failure is caused by a bad grating: After replacing the grating LS903, the machine tool will resume normal operation.
Example 7. Failure phenomenon:After a CNC hobbing machine equipped with SIEMENS PRIMOS system and 6RA26 ** series DC servo drive system, an "ERR21, X axis measurement system error" alarm occurred after starting.
Analysis and processing process: The fault analysis process is the same as the previous example, but in this example, the oscilloscope is used to check the Ual and Ua2, * Ual and * Ua2 output waveforms of the preamplifier EXE601 / 5-F of the position measurement system, and the same Ual has no output . Further inspection of the raster output (preamplifier EXE601 / 5-F input) signal waveform, found Ie1, the signal input is correct, confirm that the fault is caused by the bad preamplifier EXE601 / 5-F.
According to the principle of EXE601 / 5-F (see below for details), the signal of preamplifier EXE601 / 5-F was measured step by step, and one of the LM339 integrated voltage comparators was found to be defective; after replacement, the machine tool returned to normal operation.
Example 8. The failure phenomenon of the drive not prepared for maintenance:A horizontal machining center equipped with SIEMENS 850 system and 6RA26 ** series DC servo drive system suddenly stopped during the machining process. The "drive failure" indicator on the back panel of the machine turned on and the machine tool could not start normally.
Analysis and processing process: According to the phenomenon that the "drive failure" indicator on the panel is on, combined with the machine tool electrical schematic diagram and system PLC program analysis, it is confirmed that the machine tool failure reason is that the Y-axis driver is not ready.
Check the drive in the electric cabinet, measure the main circuit power input of the 6RA26 ** drive, only the V phase has voltage, and further check it according to the electrical schematic diagram of the machine tool. It is found that the URA and W phase fuse of the 6RA26 ** drive fast fuse. Use a multimeter to measure the 1U, 1W input end of the main circuit of the driver, and confirm that there is a short circuit inside the main circuit of the driver.
Since the main circuit incoming line of 6RA26 ** AC driver is directly connected to the thyristor, it can be confirmed that the cause of the failure is due to damage to the thyristor.
Measure the main circuit thyristors V1-V6 one by one, and confirm that V1 and V2 are bad (short-circuited); after replacing spare parts of the same specifications, the machine tool returns to normal.
Since no other parts of the driver are fault-free, after replacing the thyristor module, the machine tool resumes normal operation. The cause of the analysis may be an accidental fault caused by instantaneous voltage fluctuation or load fluctuation.
Example 9. Failure phenomenon caused by external failure caused by motor failure:An imported vertical machining center equipped with SIEMENS 6M system found that the tool magazine could not rotate normally during the tool change process.
Analysis and processing process: Through the analysis of the electrical schematic diagram of the machine tool, the tool magazine rotation control of this machine tool is a 6RA ** series DC servo drive, and the tool magazine speed is the "tool magazine given value conversion / positioning control made by the machine tool manufacturer. "Board to control.
On-site analysis and observation of the rotation of the tool magazine. It was found that when the tool magazine was rotating, the rotation signal of the PLC was input and the mechanical latch of the tool magazine was pulled out, but the conversion analog value of the 6RA26 ** driver was not input. Since the output of this analog quantity comes from the "tool magazine given value conversion / positioning control" board, the schematic diagram of the "tool magazine given value conversion / positioning control" board provided by the machine tool manufacturer is measured step by step, and finally found on the board The analog switch (model DG201) has been damaged. After replacing the spare parts of the same model, the machine tool resumes normal operation.
Example 10. The phenomenon of fault maintenance when the motor is turned on at high speed:A machine tool of the same model as Example 268, when starting up and commissioning, after manually pressing the tool magazine rotation button, the tool magazine rotates at high speed, causing the machine tool to alarm.
Analysis and processing process: According to the fault phenomenon, it can be preliminarily determined that the fault is due to the incorrect polarity of the speed feedback of the DC drive of the tool magazine or the positive feedback or open loop of the speed loop caused by the speed feedback line falling off. The measurement confirmed that the servo motor speed feedback line was connected, but the polarity was incorrect; after exchanging the speed feedback polarity, the tool magazine action returned to normal.
1. How to deal with the servo motor does not run when there is pulse output?
â‘ Monitor the current value of the pulse output of the controller and whether the pulse output lamp flashes, confirm that the command pulse has been executed and the pulse has been output normally;
â‘¡ Check whether the control cable, power cable, and encoder cable from the controller to the driver are miswired, damaged, or have poor contact;
â‘¢ Check whether the brake of the servo motor with brake has been opened;
â‘£ Monitor the panel of the servo drive to confirm whether the pulse command is input;
⑤ Run command is normal;
â‘¥ The control mode must choose the position control mode;
⑦ Whether the input pulse type set by the servo drive and the command pulse set are consistent;
⑧ Make sure that the forward rotation side drive prohibition, reverse rotation side drive 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 error of motor deviation counter overflow when the servo motor rotates at high speed?
â‘ The motor deviation counter overflow error occurs during high-speed rotation;
Countermeasure:
Check whether the wiring of the motor power cable and encoder cable is correct and the cable is not damaged.
â‘¡ A motor deviation counter overflow error occurs when a long command pulse is input;
Countermeasure:
a. The gain setting is too large, adjust the gain manually again or use the automatic gain adjustment function;
b. Extend the acceleration and deceleration time;
c. If the load is too heavy, it is necessary to reselect a motor with a larger capacity or reduce the load, and install a transmission mechanism such as a reducer to increase the load capacity.
â‘¢ A motor deviation counter overflow error occurred during operation.
Countermeasure:
a. Increase the set value of the deviation counter overflow level;
b. Slow down the rotation speed;
c. Extend the acceleration and deceleration time;
d. The load is too heavy, you need to re-select a larger capacity motor or reduce the load, add a transmission mechanism such as a reducer to increase the load capacity.
3. What should I do if the servo motor does not report overload with load?
â‘ If it occurs when the servo Run signal is connected and there is no pulse:
a. Check the power cable wiring of the servo motor, check whether there is poor contact or cable damage;
b. If it is a servo motor with a brake, be sure to open the brake;
c. Whether the speed loop gain is set too large;
d. Is the integral time constant of the speed loop set too small?
â‘¡ If the servo only occurs during operation:
a. Whether the position loop gain is set too large;
b. Whether the amplitude of positioning completion is too small;
c. Check that the servo motor shaft is not blocked, and readjust the machine.
4. How to deal with abnormal sound or jitter when the servo motor is running?
â‘ Servo wiring:
a. Use standard power cable, encoder cable, control cable, whether the cable is damaged;
b. Check whether there is interference source near the control line, whether it is parallel or too close to the large current power cable nearby;
c. Check whether there is any change in the potential of the ground terminal, and ensure that the grounding is good.
â‘¡ Servo parameters:
a. The servo gain setting is too large, it is recommended to adjust the servo parameters manually or automatically;
b. Confirm the setting of the time constant of the speed feedback filter, the initial value is 0, you can try to increase the setting value;
c. The electronic gear ratio setting is too large, it is recommended to restore the factory settings;
d. Resonance of servo system and mechanical system, try to adjust notch filter frequency and amplitude.
â‘¢ Mechanical system:
a. The coupling connecting the motor shaft and the equipment system is offset, and the mounting screws are not tightened;
b. The poor engagement of the pulley or gear will also cause the load torque to change, try no-load operation, if the no-load operation is normal, check the joint part of the mechanical system for abnormalities;
c. Confirm whether the load inertia, torque and speed are too large, try no-load operation, if the no-load operation is normal, reduce the load or replace the larger capacity drive and motor.
5. How to deal with Schneider servo motor's inaccurate position control positioning?
â‘ Firstly, confirm whether the actual value of the pulse actually sent by the controller is consistent with the expected one. If not, check and correct the program;
â‘¡ Monitor whether the number of pulse commands received by the servo driver is consistent with that issued by the controller. If not, check the control cable.
1. Panasonic's digital AC servo system MHMA 2KW, the motor vibrates and has a lot of noise as soon as the test machine is powered on, and then the driver gives an alarm No. 16, how to solve it?
This phenomenon is generally due to the driver's gain setting is too high, resulting in self-oscillation. Please adjust the parameters No.10, No.11, No.12 to reduce the system gain appropriately. (Please refer to the content about gain adjustment in the "User's Manual")
2. No. 22 alarm appears when the Panasonic AC servo drive is powered on, why?
Alarm No. 22 is an encoder fault alarm. The causes are generally:
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: misalignment, damage, etc., please send it for repair.
3. What should I do when the Panasonic servo motor is running at a very low speed, fast and slow, like crawling? The phenomenon of low speed crawling of the servo motor is generally caused by the system gain is too low, please adjust the parameters No.10, No.11, No.12, adjust the system gain appropriately, or run the driver automatic gain adjustment function. (Please refer to the content about gain adjustment in the "User's Manual")
4. In the position control mode of the Panasonic AC servo system, the control system outputs pulse and direction signals, but whether it is a forward rotation command or a reverse rotation command, the motor only rotates in one direction. Why?
Under the position control mode, Panasonic AC servo system can receive three kinds of control signals: pulse / direction, forward / reverse pulse, and A / B orthogonal pulse. The factory setting of the driver is A / B orthogonal pulse (No42 is 0), please change No42 to 3 (pulse / direction signal).
5. In the use of Panasonic AC servo system, is it possible to use servo-ON as a signal to control the motor offline in order to directly rotate the motor shaft? Although the motor can be taken offline (in a free state) when the SRV-ON signal is 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 realize the offline function, you can use the switching of the control mode to achieve: Assuming that the servo system needs 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: when performing position control, turn on the signal C-MODE to make the driver work in the first mode (that is, position control); when you need to go offline, turn on the signal C-MODE, Make the drive work in the second mode (torque control), because the torque command input TRQR is not wired, so the motor output torque is zero, thus 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. When the machine is installed and debugged, it sends a motion command and the motor will fly.
This phenomenon is caused by the wrong phase sequence of the A / B quadrature signal of the driver's pulse output feedback to the computer and the formation of positive feedback. It can be handled by the following methods:
A. Modify the sampling program or algorithm;
B. Reverse the A + and A- (or B + and B-) of the pulse output signal of the driver to change the phase sequence;
C. Modify the driver parameter No45 and change the phase sequence of its pulse output signal.
7. In a testing device we developed, we found that the Panasonic AC servo system had some interference with our testing device. What method should be used to eliminate it? Because the AC servo drive adopts the inverter principle, it is a prominent interference source in the control and detection system. In order to reduce or eliminate the interference of the servo drive to other electronic equipment, the following methods can generally be used:
A. The ground terminals of the driver and motor should be reliably grounded;
B. Add an isolation transformer and filter to the power input of the driver;
C. Use shielded wires for all control and detection signal lines.
The problem of interference is a very difficult problem in electronic technology. There is no fixed method to completely eliminate it, usually based on experience and experiment to find anti-interference measures.
8. Why doesn't the servo motor lose steps? The servo motor driver receives the feedback signal from the motor encoder and compares it with the command pulse, thus forming a semi-closed loop position control. Therefore, the servo motor will not lose steps, and every command pulse can be reliably responded.
9. How to consider the power supply problem of Panasonic servo? At present, almost all AC servo motors made in Japan are powered by three-phase 200V, and the domestic power supply standards are different.
A. For AC servo below 750W, generally, 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 change the three-phase 380V to three-phase 200V, and connect to the driver's L1, L2, L3.
10. What should I pay special attention to when installing the servo motor mechanically?
Since the rotary encoder is installed at the rear end of each servo motor, it is a very fragile precision optical device, and excessive impact force will definitely damage it.
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