Gear Failure Diagnosis Function - Mitsubishi Electric MELSERVO-J5 User Manual

Gear failure diagnosis function

The gear failure diagnosis function uses the servo motor driving status to predict a gear malfunction by estimating the
backlash amount of the gear connected to the servo motor. The gear failure diagnosis function includes the backlash
estimation function and the gear failure prediction function.
• Backlash estimation function
For the backlash estimation function, the backlash amount of the gear connected to the servo motor is estimated from the
servo amplifier internal data during the to-and-fro positioning operation. When the servo motor is at a stop, click the estimation
start button of MR Configurator2 to start. If the servo motor speed is 20 r/min or faster, pressing the estimation start button of
MR Configurator2 will not start the backlash estimation and an error will be displayed.
• Gear failure prediction function
The gear failure prediction function predicts the gear failure by comparing the backlash amount estimated by the backlash
estimation function with the backlash threshold set by the servo parameter. After inputting the backlash threshold with [Pr.
PF67 Backlash nominal value] and [Pr. PF68 Backlash threshold multiplication] and executing backlash estimation, gear
failure prediction is performed.
• When using a linear servo motor, the gear failure diagnosis function cannot be used. When the linear servo
motor is used, backlash estimation does not start as errors will occur.
• Perform backlash estimation when all the servo motors connected to the servo amplifier have been
stopped. If any of the servo motors connected to the servo amplifier are being operated, backlash
estimation is not performed as errors will occur.
Precautions
• During gear diagnosis, the servo amplifier automatically generates a command to drive the servo motor. Even if the servo
motor moves by the travel distance + 1 rotation during gear diagnosis, ensure that the movable part does not collide with
the equipment, then execute backlash estimation. Use the stroke limit or EM2 (Forced stop 2) during the gear diagnosis.
• The gear failure diagnosis function can be used for the gears with backlash amount of 0.1 degree in the servo motor shaft
conversion. If the backlash estimation is performed on the gears with the backlash amount of less than 0.1 degree, the
error between the estimated value and true value becomes too large, causing an incorrect detection of [AL. 0F7 Machine
diagnosis warning]. Also, [AL. 0F7 Machine diagnosis warning] may not be detected during a gear malfunction.
• The gear failure diagnosis function can be used only when the load to motor inertia ratio is two times or more. If backlash
estimation is performed when no load is applied or when the load to inertia ratio of the connected load is less than two
times, the error between the estimated value and the true value becomes too large, causing an incorrect detection of [AL.
0F7 Machine diagnosis warning]. [AL. 0F7 Machine diagnosis warning] may not be detected during a gear malfunction.
• Once backlash estimation is performed, the servo amplifier will enter the test operation mode and control commands from
the controller will not be available. After executing the backlash estimation, reset the communication or cycle the power of
the servo amplifier.
• If the overspeed alarm level and the torque limit value are too small, the backlash estimation may fail.
• If the gear diagnosis is executed simultaneously on two or more axes in the equipment with mechanical interference, the
equipment may malfunction. Execute the gear diagnosis on one axis at a time.
• Adjust the gain before executing the backlash estimation so that the equipment does not oscillate or vibrate. The backlash
estimation estimates the backlash from the servo motor drive status during the to-and-fro operation. If the equipment
oscillates/vibrates, the error between the backlash estimate and the actual value may be too large.
• If the gear ratio on the load side is too large, the backlash estimate accuracy may deteriorate.
• When executing the backlash estimation on the MR-J5_-_B_, assign both FLS (Upper stroke limit) and RLS (Lower stroke
limit) to the servo amplifier. When backlash estimation is executed with them assigned to the controller, "C007" is displayed
in the error code status.
4 APPLICABLE FUNCTIONS
4.5 Machine diagnosis
4
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