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Thread: 1984 Leadwell 550S w Fanuc 3MC Spindle runaway/malfunction

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    Default 1984 Leadwell 550S w Fanuc 3MC Spindle runaway/malfunction

    I am retired and do not turn on my machine very much.
    Today I went to the shop to putter around and turned on the Leadwell and got a battery alarm. So I changed the batteries.

    I don't know if this has anything to do with the battery change or not, but now when I manually turn on the spindle, it revs up much faster than the 6000 max and then alarms out and coasts to a stop. When I enter an M3 S500 command, with MDI, it starts to go for a second and then alarms out. I tried an M4 command, same thing. Tried to run a little test program same thing. All the axis still move, just the spindle having fits

    Can't really afford a repair man as I am not making money with this machine anymore and I am on a fixed income.

    I know these machines aren't worth much, but it was nice to have it around to do hobby things with once in a while.

    Any help would be much appreciated

    G

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    Default Re: 1984 Leadwell 550S w Fanuc 3MC Spindle runaway/malfunction

    Hello and welcome to the forum,

    2 questions right away:

    a) When you replaced the batteries, was the machine ON or OFF?

    It is always recommended to replace the backup batteries with the power being ON, otherwise parameters, offsets, etc; can get lost.

    b) Do you know if your spindle is driven by a DC or AC motor?

    In old DC spindle motor systems, they used to put a tachogenerator for speed feedback, an small rotor was mounted at the rear end of the spindle motor, and would generate a little DC voltage according to the speed reached. That small rotor used 2 (or 4) small brushes that would pickup the small DC voltage and send it to the spindle drive. But when that "speed feedback system" failed (bad windings, brushes, backwards or broken connections to the spindle drive), the spindle itself would "runaway", sometimes with catastrophic results.

    Please let us know what you find about this.

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    Default Re: 1984 Leadwell 550S w Fanuc 3MC Spindle runaway/malfunction

    Thank you for your thoughts
    I just looked and it says "Fanuc AC Spindle Motor Number 6"

    I'm not sure if they power was on or off. If it was off and parameters were lost can they be replaced?

    However the problem was occuring before I replaced the batteries and I replaced them as part of what I thought would be a remedy

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    Default Re: 1984 Leadwell 550S w Fanuc 3MC Spindle runaway/malfunction

    Ok,

    Then I think your Fanuc 3MC parameters are not lost.

    But, how about your AC spindle drive parameters?

    Take a look at your spindle drive, the big metal box, most likely you have a Fanuc brand in there. It also uses parameters, you can check their values if it has an small red display, there is an special procedure to read and to re-write those values. Fisrt post here the whole drive Fanuc number (located in the rear bottom end of the metal box) and also post here the number of the top main board of this drive, the numbers look like A06B-XXXX-XXXX.

    Also, check and see if your machine uses an spindle encoder for speed feedback, sometimes it is belt-driven and the belt wears out or breaks itself. Do you remember if you were able to see the actual spindle speed at one of your screens, MDI's screen for instance? How does it look like now, when you command say 2000 rpm, what does it show before running away or alarming out?

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    Default Re: 1984 Leadwell 550S w Fanuc 3MC Spindle runaway/malfunction

    Quote Originally Posted by Sinumeriko View Post
    Ok,

    Then I think your Fanuc 3MC parameters are not lost.

    But, how about your AC spindle drive parameters?

    Take a look at your spindle drive, the big metal box, most likely you have a Fanuc brand in there. It also uses parameters, you can check their values if it has an small red display, there is an special procedure to read and to re-write those values. Fisrt post here the whole drive Fanuc number (located in the rear bottom end of the metal box) and also post here the number of the top main board of this drive, the numbers look like A06B-XXXX-XXXX.

    Also, check and see if your machine uses an spindle encoder for speed feedback, sometimes it is belt-driven and the belt wears out or breaks itself. Do you remember if you were able to see the actual spindle speed at one of your screens, MDI's screen for instance? How does it look like now, when you command say 2000 rpm, what does it show before running away or alarming out?



    The serial on the drive unit is
    A068-6044-H008

    In front of the dive unit there is mounted a large board with the number
    A20B-0009-0531
    on it.

    It has 5 LEDs
    the one to the far left is green and is always on
    there are 4 to the right of it with the numbers 8 4 2 1 above each LED
    when the spindle alarms out the LEDs under 4 2 1 turn on and are red
    When I hit reset on the operator's panel they go out

    I have looked over the spindle drive motor and there are no tachs that I can see above or below or to the side.
    There is a box mounted to operators side of the spindle motor that is about 7" sqaure, but there seems to be nothing visually wrong in there.
    There looks like there might be something that looks like a prox sensor, but I may be wrong.
    I did not think to look at the spindle to see if there is a tach on it, but I will when I go back down (the spindle motor and the spindle are connected via a cogged belt)

    I do not remember an RPM counter on the MDI pages. I looked just now and there is no place for one.
    There is an analog RPM meter/indicator on the operators panel.
    There is also a power meter
    When the motor starts the power meter goes up into the red zone for a moment and then back down, but it has always done that since I bought it new.

    Thanks you again for taking the time to think about this.
    It is a real lift for the spirits

    G

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