Help needed - FANUC servo motor and pulsecoder after service

  • Hi,
    I am in need of help. I have an old FANUC robot M710i with RJ2 Controller. I recently had to remove and disassemble a motor to replace the axis bearings. The problem is the motor won't start after I put it back in. It get's powered up, I can hear the brake released but no motion from the axis. After 2-3 seconds OVC alarm hits. Sometimes it turns but the motion is jerky, bumpy. Is it a pulsecoder issue ? In situations like this that I have to remove a motor for bearing service is there a procedure I must follow when I assemble and disassemble the pulsecoder from the motor ? Can I directly enter the pulsecoder data of the serviced motor that was stored from the last MASTERING in DMR GROUP sys variable ? Should I mark the pulsecoder position somehow and position the axis there during assemble procedure ?

    I always put the robot in zero degree position when I service or replace a servo motor.

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  • The OVC indicates something is wrong inside the motor in this case. It has nothing to do with the pulse coder.
    There is no way to put the "data" back in the pulse coder other than mastering the axis once the pulse coder has been unplugged. You may be able to use quick master if you set quick master reference prior to removing the motor. You should have had a BZAL alarm on the axis the motor was removed from. Then you would reset the pulse coders from the master cal menu and then cycle power.

    Once the pulse coder connector has been removed you must master and calibrate the axis.

  • Hi, We're making a faulty engine change. This is what we do. We're taking the robot to zero. We place mechanical support on many points before we dismantle the engine. We replace an engine that is exactly the same as the one we replaced and the same as the palscoder model. We add new grease without moving their support. We open the robot in cold start mode and increase the axis limits. We do "SPC reset and Res SCA" and we do "Mas count true" without changing the old calibre values from DMR group menu. After turning it on and off again, we calibrate the axle motor, which we just changed from the calibration menu. It's a long time to work, but if you did everything right, it works fine. Despite all this, if there is still sound, there is a mechanical problem from the engine. "OVC alarm" is usually a problem with your cable, or your software values and engine values are mismatched and difficult to do.

  • Regarding the OVC:
    I would remove the motor and try releasing the brake and see if the motor easily turns by hand. About 50VDC will release the brake and it should stay released until <40VDC. Hearing the brake release and having it actually release can be different.
    Bearing fit and alignment in the motor are critical to having the motor last. If not done right, it could cause binding.
    Was this a problem before replacing the bearings? Besides the brake, could be the armature or stator gone bad.

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