Siemens, Schneider and Panasonic servo drive repair common problems and solutions

First, Siemens DC servo drive system fault repair 10 cases

example 1. Faulty maintenance failure phenomenon of incoming line fast fuse blown: A horizontal machining center equipped with SIEMENS 8MC is turned on after the power grid is suddenly powered off, and the system cannot be started.

Analysis and processing: After inspection, the incoming line fast fuse of the X-axis servo drive of the machine tool has been blown. The feed system of the machine uses the SIEMENS 6RA series DC servo drive. The servo motor and the drive are inspected against the drive. No damage or short circuit of any components is found.

Check that the mechanical part of the machine tool is working normally. 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 failure of the power grid.

Example 2. SIEMENS 8MC measurement system failure repair failure 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 prompt appears: the Y-axis measurement system is faulty. After the power is turned off and on again, the machine can resume normal operation, but the same fault may occur when the X-axis moves to a certain position.

Analysis and processing: The machine is an imported horizontal machining center with SIEMENS 8MC CNC system and SIEMENS 6RA series DC servo drive. Since 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 in the system. Therefore, the cause of the system false alarm can be eliminated.

Check that the X-axis is in the vicinity of the alarm and it is found that it has no interference and influence on the Y-axis measurement system (grating), and only moves the Y-axis without alarm, and the Y-axis works normally. The Y-axis motor cable plug, grating readhead and scale were checked for no abnormalities.

Considering that the equipment is a large-scale machining center, there are many cables, the cable length between the electric cabinet and the machine tool is long, and all the cables are fixed on the cable rack, and the random bed moves back and forth. According to the above analysis, it is preliminarily judged that the possibility of partial disconnection is large due to the bending of the cable.

During the maintenance, the X-axis is intentionally moved to the position where the fault occurred. The cable is manually moved. The connection of each feedback signal line on the Y-axis is carefully measured. Finally, one of the signal lines is occasionally appeared during the continuous movement of the cable. Open circuit phenomenon; after replacing the disconnection with the spare line in the cable, the machine tool returns to normal.

Example 3~Example 4. Drive fault caused by the following error tolerance alarm repair failure phenomenon: a matching SIEMENS PRIMOS system, 6RA26** series DC servo drive system CNC gear hobbing machine, after moving the Z axis of the machine tool, the system occurs "ERR22 following error tolerance" alarm.

Analysis and processing: The following error occurs in the CNC machine tool and exceeds the alarm. The essence is that the actual machine tool cannot reach the position of the command. The cause of this failure is usually the fault of the servo system failure or the machine mechanical drive system.

Since the servo feed system of the machine tool has a full closed loop structure, it cannot be tested by disconnecting the motor from the mechanical part. In order to confirm the fault location, firstly, when the machine is powered off and the clamping mechanism is released, the Z-axis screw is manually rotated. No abnormality of the mechanical transmission system is found. It is preliminarily determined that the fault is caused by the servo system or the numerical control device. .

In order to further determine the fault location, when the system is switched on, 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 DC. The speed of the drive is given a voltage. It is checked that the speed is given a voltage input, and the 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 malfunction is caused by the malfunction of the servo driver.

Check the drive and find that the drive's own status indicator has no alarm and basically eliminates the fault of the drive's main circuit. Considering that the X and Z axis drive models of the machine are the same, confirm the faulty part of the A2 board of the 6RA26** DC drive by switching the drive board one by one.

According to the schematic diagram of SIEMENS 6RA26** series DC servo drive, check and measure each level of signal one by one, and finally confirm that the cause of the fault is caused by the failure of the integrated voltage comparator N7 (model: LM348) on the A2 board: after the replacement, the machine is restored. normal.

Example 4. Fault phenomenon: an imported horizontal machining center with SIEMENS 850 system and 6RA26** series DC servo drive system. After starting the machine, manually move the X axis, the X axis table of the machine does not move, and the CNC has an X following error error alarm. .

Analysis and processing: Since the other axes of the machine tool are working normally, the X-axis drive has no alarm, and all the status indicators indicate no fault. In order to determine the fault location, the speed/current adjustment board A2 of the 6RA26** series DC servo drive is considered the same. During the repair, the A2 board of the X-axis drive was tested against the A2 board of the Y-axis drive. It has been found through experiments 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 speed/current regulator board of the X-axis drive is poor. According to the schematic diagram of SIEMENS 6RA26** series DC servo drive, the measurement check found that when a small amount of X axis is moved, there is an analog input between the speed reference input terminals 57 and 69 of the driver, and the detection terminal B1 is measured. The speed analog voltage is correct. However, the 6-pin output of the speed proportional regulator N4 (LM301) is always 0V.

Check the feedback resistors R25, R27, R21 of the speed regulator LM301, the offset adjusting resistors R10, R12, R13, R15, R14, R12, and the input protection diodes V1 and V2 of the LM301, given the principle diagram. C1, R20, V14, peripheral components such as R27, R28, R8, R3, C5, and R4 in the speed feedback filter section, confirm that all components are fault-free.

Therefore, it is confirmed that the cause of the fault is caused by the poor operation of the LM301 integrated operation amplifier; after the LM301 is replaced, the machine tool resumes normal operation and the fault is eliminated.

Example 5. CNC fault causes follow-up error tolerance alarm repair

Fault phenomenon: A CNC hobbing machine with a SIEMENS PRIMOS system and a 6RA26** series DC servo drive system. After starting the machine, the Z axis of the machine tool is moved, and the system has an alarm of “ERR22 following error tolerance”.

Analysis and processing: 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 the handwheel, the speed of the Z-axis DC drive is always set to 0, so the fault can be preliminarily determined in the numerical control device or numerical control. Connect the cable to the drive.

Check that the cable connection between the CNC unit and the drive is normal, and confirm the cause of the fault in the CNC unit. Turn on the numerical control device check and find that the speed of the Z axis is correct for the digital input of the output D/A converter, but there is no analog output, so that the fault is caused by the D/A converter.

After replacing the Z-axis speed given output of the 12-bit D/A converter DAC0800, the machine is restored

Example 6. Fault phenomenon: A CNC hobbing machine equipped with SIEMENS PRIMOS system and 6RA26** series DC servo drive system, “ERR21, Y-axis measurement system error” alarm occurs after power-on.

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

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

2) The connection cable between the numerical control device and the position detecting component is defective.

3) The position measurement system itself is defective.

Since the servo drive system of this machine adopts a full-closed structure, the detection system uses the grating of HEIDENHAIN. In order to determine the fault location, the X and Y axis speeds output by the numerical control device are first given during maintenance, and the drive enable and the position feedback of the X and Y axes are reversed, so that the numerical control X-axis output controls the Y-axis and the Y-axis output. Control the X axis. After the adjustment, the CNC system is operated, the Y axis is manually moved, the machine X axis generates motion, and the work is normal, which proves that the position feedback signal interface circuit of the numerical control device has no fault.

However, the CNC system is operated, the X axis is manually moved, and the Y axis of the machine tool is not moved. At the same time, the numerical control displays the alarm "ERR21, X axis measurement system error". It is thus confirmed that the alarm is caused by a defective position measuring system and is independent of the interface circuit of the numerical control device. Check that the measurement system cable connections are correct and reliable, eliminating the problem of cable connections.

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 the Ua1 phase has no output. Further check the signal output of the raster output (input of the preamplifier EXE601/5-F) and find that Ie1 has no signal input. Check that the grating of this machine is installed correctly, and confirm that the fault is caused by the bad grating: after replacing the grating LS903, the machine will resume normal operation.

Example 7. Fault phenomenon: A CNC hobbing machine equipped with SIEMENS PRIMOS system and 6RA26** series DC servo drive system, “ERR21, X-axis measurement system error” alarm occurs after power on.

Analysis and processing: 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 measuring system, and it is found that the same Ual has no output. . Further check the signal output of the raster output (the input of the preamplifier EXE601/5-F), find Ie1, the signal input is correct, and confirm that the fault is caused by the defective preamplifier EXE601/5-F.

According to the principle of EXE601/5-F (see below), 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. Faulty maintenance faults of the drive: A horizontal machining center equipped with SIEMENS 850 system and 6RA26** series DC servo drive system suddenly stops during processing, and the “Drive Fault” indicator on the rear panel of the boot is on. The machine does not start properly.

Analysis and processing: According to the phenomenon that the “Drive Fault” indicator on the panel is on, combined with the machine electrical schematic and the system PLC program analysis, it is confirmed that the cause of the machine fault is that the Y-axis drive is not ready.

Check the driver in the cabinet and measure the main circuit power input of the 6RA26** driver. Only the V phase has voltage. According to the electrical schematic of the machine tool, it is found that the U and W phases of the 6RA26** driver incoming fuse are blown. Use a multimeter to measure the 1U and 1W of the main circuit input terminal of the driver, and confirm that there is a short circuit inside the main circuit of the driver.

Since the 6RA26** AC driver main circuit incoming line is directly connected to the thyristor, it can be confirmed that the cause of the fault is due to thyristor damage.

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

Since there is no fault in other parts of the drive, after the thyristor module is replaced, the machine tool resumes normal operation, and the analysis may be an accidental fault caused by instantaneous voltage fluctuation or load fluctuation.

Example 9. Faults caused by external faults that cause the motor to not rotate. Repair phenomenon: An imported vertical machining center supporting the SIEMENS 6M system found that the tool magazine could not rotate normally during the tool change process.

Analysis and processing: Through the electrical schematic diagram analysis of the machine tool, the tool magazine rotary control of the machine tool adopts 6RA** series DC servo drive, and the tool magazine rotation speed is “tool magazine setpoint conversion/positioning control” manufactured by the machine tool manufacturer. "The board is controlled.

On-site analysis and observation of the tool magazine rotation action, when the tool magazine is rotated, the PLC rotation signal has been input, the tool magazine mechanical bolt has been pulled out, but the 6RA26** drive conversion given analog input is not input. Since the output of the analog quantity comes from the “tool magazine setpoint conversion/positioning control” board, the schematic diagram of the “tool magazine setpoint 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) is damaged. After replacing the same type of spare parts, the machine returns to normal operation.

Example 10. The faulty maintenance fault phenomenon of the starting motor is the high-speed rotation: one machine with the same model as the example 268, when the machine is pressed and the rotary button is pressed manually, the tool magazine is rotated at a high speed, causing the machine tool to alarm.

Analysis and processing: According to the fault phenomenon, it can be preliminarily determined that the fault is due to the incorrect polarity of the speed feedback feedback of the DC drive of the tool magazine or the speed loop feedback or open loop caused by the falling of the speed feedback line. The measurement confirms that the servo motor speed feedback line is connected, but the polarity is not correct; after exchanging the speed feedback polarity, the tool bank operation returns to normal.

Second, Schneider servo drive common fault analysis and solution

1. The servo motor does not run when there is a pulse output. How to deal with it?

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

2 Check the controller to drive control cable, power cable, encoder cable for wiring errors, breakage or poor contact;

3 Check if the brake of the servo motor with brake is open;

4 Monitor the panel of the servo drive to confirm whether the pulse command is input;

5 Run run command is normal;

6 Control mode must select the position control mode;

7 The input pulse type set by the servo driver is consistent with the setting of the command pulse;

8 Make sure that the forward side drive is prohibited, the reverse side drive inhibit signal and the deviation counter reset signal are not input, the load is released and the no-load operation is normal, and the mechanical system is checked.

2. When the servo motor rotates at high speed, the motor deviation counter overflow error occurs. How to deal with it?

1 Motor deviation counter overflow error occurs during high speed rotation;

Countermeasures:

Check that the motor power cable and encoder cable are wired correctly and that the cable is damaged.

2 A motor deviation counter overflow error occurs when a longer command pulse is input;

Countermeasures:

a. The gain setting is too large, re-adjust the gain manually or use the auto-adjust gain function;

b. Extend 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 install a transmission mechanism such as a reducer to increase the load capacity.

3 A motor deviation counter overflow error occurred during operation.

Countermeasures:

a. increase the deviation counter overflow level setting value;

b. slow down the rotation speed;

c. Extend the acceleration and deceleration time;

d. If the load is too heavy, it is necessary to re-select a larger capacity motor or reduce the load, and install a transmission mechanism such as a reducer to improve the load capacity.

3. The servo motor does not report overload with load. How to deal with it?

1 If the servo Run signal is connected and no pulse is generated:

a. Check the servo motor power cable wiring to check for 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. Whether the integral time constant of the speed loop is set too small.

2 If the servo only happens during the run:

a. Whether the position loop gain is set too large;

b. Whether the positioning completion amplitude is set too small;

c. Check that there is no stall on the servo motor shaft and re-adjust the machine.