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  1. #1
    Join Date
    Jul 2007
    Posts
    10

    tacho generator disconnected

    as soon as the machine is switched on "tacho generator disconnected"alarm appears.can someboby help fast

  2. #2
    Join Date
    Dec 2003
    Posts
    24216
    No output from the Spindle Tach on the end of the spindle shaft, what machine?
    If you pull the spindle over manually, you should see a plus minus DC voltage out of the tach depending on direction, the level depending on speed, check the tach brushes.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  3. #3
    Join Date
    Jul 2007
    Posts
    10
    it is a fanuc all electric molding machine pretty old may be 1994 make. this perticular servo is y axis

  4. #4
    Join Date
    Dec 2003
    Posts
    24216
    Substitute Yaxis servo for reference to spindle in my first post, they must be DC servo's with a tach on them.
    Remove motor or disconnect drive coupling to test., spin it over by hand and see if dc output from the tach, check all the Main armature brushes while you are about it.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  5. #5
    Join Date
    Jul 2007
    Posts
    10
    this particular machine the fanuc motors are black body with red caps for the encoder(if color of the two is of any relevance as to know which type a/c , d/c etc).when the motor shaft is rotated by hand, the reading on the monitor changes accordingly, does this feed back help?

  6. #6
    Join Date
    Dec 2003
    Posts
    24216
    Red Cap, then they are AC servo's.
    Try swapping two motors over, if they are the same size to eliminate the encoder, I have never seen tach loss message on AC servo's?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  7. #7
    Join Date
    Jun 2007
    Posts
    43
    I have, I suspect that this alarm is an early days hang over from the change from DC to AC, quite often a wire break on the motor thermal sensor

  8. #8
    Join Date
    Jul 2007
    Posts
    10
    we checked the drive card, there was a problem with what the expert said "module", which after replacement , the alarm message is gone. But we have a new problem. now , i think its because the encoder cable was disconnected from the drive and hence it has lost its Y position value,the new alarm says, "return to original position - Y".We donot know if there is any homing to be done for Injection Molding machine like VMCs,CNC Lathes.But otherwise we dont 'home' the machine at every 'power-on'

  9. #9
    It seems to be a absolute pulse coder. Normally we will made Zero return afer the Drive service or Backup Battery of the Encoder fail. Once did ZRN after that is not required to ZRN. Check up with your manual for procedure.

  10. #10
    Join Date
    Jul 2007
    Posts
    10
    how to do ZRN for absolute encoder. can u pl help

  11. #11
    Join Date
    Mar 2007
    Posts
    1

    Zrn

    What is the control for ex. 15M, 15 IM,21Im ...
    we need that info to give you a procedure for it
    Djack

  12. #12
    Join Date
    Jul 2007
    Posts
    10
    it is a fanuc 10 tf control

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