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  1. #1

    Join Date
    Mar 2006
    Posts
    107

    401 servo alarm (VRDY OFF), at turn on, Fanuc OM SOLVED

    Eveything was OK with machine, until we have moved it from place to place, just for one meter, by hand, carefully, and cleaned (washer) it, also carefully.

    Now when I turn it on (main pow, nc control) and i pull out emergency stop, this alarm appears

    401 SERVO ALARM: (VRDY OFF)

    And I can't get rid of it, I push reset, it appears again, pull in/out EM STOP, alarm appears again.

    Machine is not movable (nor in handle mode).
    I have tryed to turn it off and on for several times, but no progress.
    And on servo amplifiers there is no alarm code, just " - " as not ready.

    I have red lot about this alarm, but it could be anything (wires, relays, amplifier, servo brushes, dirty servo.....?)

    And read again my first sentance, it may be important for finding solution.

  2. #2

    Join Date
    Sep 2005
    Posts
    755
    You may have a limit switch that has stuck open or become shorted by the washing process. Look for limit switches on each axis (in both + and - direction). There are frequently TWO limit switches in each direction. One limit switch simply causes an Overtravel (OT) alarm, and you can then jog in the oposite direction to move off the switch. The second switch is an "Extreme" overtravel switch, and it is designed to protect the ballscrews and stop the servo positively if the first switch should fail, or if the CNC should ignore the OT switch. On some machines, that switch is tied to the 24v E-stop circuit, which will simply make the machine come up "NOT READY". Other machines, however, use the 100vac circuit to enable the servo contactors for that same purpose. If your machine is wired like this, and one of these switches was stuck on, filled with water, or otherwise defective, you will get your 401 servo alarm. Also look for damaged cables from these switches to the CNC, and inspect any connectors you may find along these cables. These extreme overtravel switches are usually wired as "normally closed" and are in series, so actuating any one of them breaks the circuit and shuts down all the servos.

  3. #3

    Join Date
    Mar 2006
    Posts
    107
    Thanks for help, machine was in "middle" position, far from limit switches.

    Actually I have just solved the problem

    Silly me, we have reconected main power input to tramsformer, and one wire (one phase) was not tightened well, and there were just two phases connected.

    (nuts)

    Thanx

  4. #4

    Join Date
    May 2008
    Posts
    79
    Hi all.
    I have the same problem: The alarm " 401" appear on screen when power on, I checked all wires, and can not find the reason. Pls. help me to fix this problem.
    Thanks

  5. #5

    Join Date
    May 2008
    Posts
    79
    Pls., Pls. help me.

  6. #6

    Join Date
    Aug 2008
    Posts
    7
    you have to check the power supply for the axis card it has some pines where you can test 25v 10v -25v or something like that maybe you transformator is broken

  7. #7

    Join Date
    May 2008
    Posts
    79
    Dear robertox
    Thanks for your reply, but I checked all the wires and voltage, all it are normally( the machine was work fine before). Is there some thing else?
    Did you know how to turn on F148.6, it will turn on Y51.2 then show up the procedure.
    Thanks

  8. #8

    Join Date
    Sep 2004
    Posts
    206
    Remove the cap from each axis motors and remove any brush dust (be careful, it's probably toxic!) and inspect/clean the commutator. While you're at it, check the brush length/condition and replace as required.

    I was getting persistant 401 errors on my mill and cleaning out the X and Y motors got rid of them almost completely. I still get the occasional 401 error, but I can usually clear it with one off/on cycle and it's probably because I didn't clean out the Z motor (which is buried in the machine casting).

  9. #9

    Join Date
    May 2008
    Posts
    79
    Dear Scirchen
    Thanks for your reply, I'll check it tonorow.

  10. #10

    Join Date
    May 2008
    Posts
    79
    Dear skirchen
    I checked already, this is AC motor, do you mean I need to check at encoder? But it's have no too. Pls. help me. Do you have servo amplifier manual( it's code AB-1003-O86), if yes, pls. sent it to me( e-mail: namnp2007@gmail.com)
    Thanks for your time

  11. #11

    Join Date
    Sep 2004
    Posts
    206
    Namnp2007,

    I'm not 100% sure, but I think that AC motors don't have brushes, so my fix isn't going to work for you. There are lot's of things that it could be; do a google search for "fanuc 401" and you will get lots of results. That's where I got the idea to clean out the brushes .

    Fanuc is a good source for the manuals (http://www.fanuc.co.jp/en/contact/index.htm). Plus, their tech department is usually very good about debugging problems over the phone, even if you bought the machine used. I once had a tech on the phone for over an hour; I was checking things on the machine while he was feeding me instructions.

    Chris Kirchen

  12. #12

    Join Date
    May 2008
    Posts
    79
    Ok, thanks.

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