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Thread: BNC 34t Alarms

  1. #1
    maximus69th Guest

    Default BNC 34t Alarms

    After a crash alarms came up which i have been unable to clear.
    401 servo alarm: (vrdy off).
    410 servo alarm; X axis ecess err.
    I have restarted the control panel while holding the P & cancel but still no joy.
    Have checked trip switches and followed all checking procedures as far as i can in the fanuc maintanence manual.
    There are no fault lights come up on the velocity control board for the X.
    Don't know what to try next.
    The control is a Fanuc OT model A
    Last edited by maximus69th; 02-11-12 at 02:23 PM.

  2. #2
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    Default Re: BNC 34t Alarms

    Sounds like something is bound up on the ballscrew whether it be the ballscrew bearings or the ballnut itself. Pull back the waycovers for the axis and see if you can turn the screw by hand. Sometimes there is an allen bolt in the end of the screw as well. It should be pretty free otherwise the coupling may also have some pin holes that you can turn the screw with. Since it was crashed it is highly likely a mechanical bind of some kind, my first guess is the ballnut 2nd would be the bearings.

  3. #3
    maximus69th Guest

    Default Re: BNC 34t Alarms

    Have removed the drive motor and turned the ball screw by hand which moves freely. have also checked any keyways and there keys.

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    Default Re: BNC 34t Alarms

    This does not correspond with the crash but the next thing I would check is your motor 3 phase lines to ground with a megohm meter. If the wires are coolant soaked or shorted in anyway that would also cause an excess error.

  5. #5
    maximus69th Guest

    Default Re: BNC 34t Alarms

    Have had an electrical bloke come in and he has checked the 3 phase's. No problems found there.

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    Default Re: BNC 34t Alarms

    Check Diagnostic 800 and watch the following error when you reset Estop. Check to see if the X motor jumps at that time. The crash could have damaged the encoder. You can also raise the parameter for allowable error while stopped. This will cause the motor to stay on longer. Of course this is only safe if the motor is disconnected and you have the X head blocked up.

  7. #7
    maximus69th Guest

    Default Re: BNC 34t Alarms

    The motor does jump when i reset the estop.

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    Default Re: BNC 34t Alarms

    When the motor twitches, you should see the following error jump on Diagnostic 800. When that number exceeds the parameter setting for allowable error at stop, you get the 410 alarm. If the encoder is damaged, you may get no counts of following error. This can also cause an alarm because the control expects to see some feedback when it excites the motor. Depending on whether the encoder is motor mount or ball screw mount will also effect the feedback loop. You can swap the command, feedback, and motor cables in various combinations to determine if the control, drive, or motor/encoder is at fault. If you need help doing this, let me know and I'll break it down for you.

  9. #9
    maximus69th Guest

    Default Re: BNC 34t Alarms

    Any help and a break down for this procedure would be appreciated.

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    Default Re: BNC 34t Alarms

    Important question: Was crash caused by operator or programming problem? Did machine run away and crash for no apparent reason?
    Assuming the encoder is mounted on the motor, you can leave the machine in Estop and turn the motor shaft while watching Diag. 800. You should see if count up and down. NOTE: some machines won't update this display while in Estop. Try turning Z and see if 801 changes. You can check the drive by swapping the command cable and motor leads with the Z axis. If the drive is bad, this will change the alarm to a 420 alarm. You can check the control by swapping the command and encoder cables between X and Z. If the control is bad, the alarm will change to a 420.
    Another possiblity, the older Fanuc controls used to store drift compensation. When a crash or drive fault happened, it could store a large enough number in the parameter that would cause the motor to jump and fault when the compensation kicked in. I don't remember if the OT-A did that or not. Just something to check. Happy Hunting!

  11. #11
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    Default Re: BNC 34t Alarms

    BTW, if you need control parts, I've got a complete OT-A control from a running machine, plus a dual axis drive. If you're interested, I can give you part numbers and we'll work out a deal.

  12. #12
    maximus69th Guest

    Default Re: BNC 34t Alarms

    The machine crashed while setting up.
    The main turret crashed into the stop mounted on the sub turret due to a program error (a m90 waiting code in the wrong position)
    Thank you for the advice.
    It may be a while for i get back but will keep you posted.
    Last edited by maximus69th; 02-19-12 at 12:25 AM.

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