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IndustryArena Forum > CNC Electronics > Spindles / VFD > Spindle: all 4 pins are grounded
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  1. #1
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    Spindle: all 4 pins are grounded

    My first spindle (water cooled, 1.5kW, ER11) had a issue with the bearings (it would scream about about 13,000rpm). I'm installing the replacement spindle (water cooled, 1.5kw, ER16) and I've discovered that all 4 pins are grounded. I've told the supplier and expect them to help, but I've already waited 6 weeks for the replacement to arrive and don't want to wait that much again. Has anyone experienced this issue and/or can anyone give advice on something simple I could look for to fix this?

    Thanks,
    Allistar.

  2. #2
    Community Moderator Al_The_Man's Avatar
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    Re: Spindle: all 4 pins are grounded

    What did you use to test and what was the actual resistance?
    CNC, Mechatronics Integration and Custom Machine Design

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

  3. #3
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    Re: Spindle: all 4 pins are grounded

    I used a multimeter and had is set to the "beep" function so it beeps when there's a connection. The supplier has told me it's like the ground wire is pinched underneath the cap and that I shouldn't try and fix it myself. They're sending a replacement. Annoying to have to wait weeks longer. Thanks anyway.

  4. #4
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    Re: Spindle: all 4 pins are grounded

    Only the ground pin should "beep" to the spindle case. If any other pins "beep" to the case, you either have a fried winding, or a short in the wiring.

    It could be something as simple as a pinched wire, as your supplier said (which means poor assembly practices and/or poor quality control).

  5. #5
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    Re: Spindle: all 4 pins are grounded

    Hi,
    multi meters are poor devices for measuring low resistances.

    I use a Kelvin bridge and it can measure resistances down to micro-ohms, but say as low as 10mili-ohm at 1% accuracy. I would suggest asking a motor re-wind company to
    measure the resistances for you. Having said that the ground wire alone should be connected to the motor casing, the other three should be meg-ohms to the casing.

    Craig

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    Re: Spindle: all 4 pins are grounded

    Quote Originally Posted by joeavaerage View Post
    Hi,
    multi meters are poor devices for measuring low resistances.
    They are perfectly good to check for an open winding, or for a short between the winding and the ground, or for a short between the winding leads. I would say, that covers 99% of the cases.

  7. #7
    Community Moderator Al_The_Man's Avatar
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    Re: Spindle: all 4 pins are grounded

    Of course, it would only take one of the motor conductors that was grounded to show a GND on all three, it would register as such due to the low resistance between each winding.
    Remove the connector screws to examine below the connector to check for a pinched wire etc.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
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  8. #8
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    Re: Spindle: all 4 pins are grounded

    Quote Originally Posted by allistar View Post
    I used a multimeter and had is set to the "beep" function so it beeps when there's a connection. The supplier has told me it's like the ground wire is pinched underneath the cap and that I shouldn't try and fix it myself. They're sending a replacement. Annoying to have to wait weeks longer. Thanks anyway.
    All 3 phases U V W will beep if you are using continuity check, but not each phase to Ground, Spindle Body to U V W.

    It is quite normal for someone to wire these spindles incorrectly, you don't have much room for the wire connections, the Plug pins need to be insolated.

    First check the wiring you did in the plug, this is where most of the problems happen.

    Yes you should remove the top cap this is normal. to have to do this to attach the Ground wire, a pinched Ground wire is not going to short all 3 phases to Ground, each pin would have to be connected to Ground for this to happen

    If the spindle motor is fried then it is possible that each phase has a short to Ground, this normally happens with incorrect Parameters set in the VFD Drive
    Mactec54

  9. #9
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    Re: Spindle: all 4 pins are grounded

    Quote Originally Posted by mactec54 View Post
    a pinched Ground wire is not going to short all 3 phases to Ground, each pin would have to be connected to Ground for this to happen
    I am assuming the OP measured between pins with the VFD disconnected!
    And a short to GND on one of the phase pins is going to register on all, the coil resistance on these motors is very low.
    It would register a short on all three particularly using a 'Beeper' setting which is usually diode check on a meter and actually measure volt drop for diode testing.NOT resistance.
    CNC, Mechatronics Integration and Custom Machine Design

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

  10. #10
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    Re: Spindle: all 4 pins are grounded

    Quote Originally Posted by Al_The_Man View Post
    I am assuming the OP measured between pins with the VFD disconnected!
    And a short to GND on one of the phase pins is going to register on all, the coil resistance on these motors is very low.
    It would register a short on all three particularly using a 'Beeper' setting which is usually diode check on a meter and actually measure volt drop for diode testing.NOT resistance.
    Correct, this would be a spindle motor problem, if this was the case.

    There is no Ground wire, that can be pinched, unless he has had the top off and add a Ground wire, which by what he posted he had not had the top off, very few come with the Ground pin connected, to anything.

    The only other way is if he checked it with the spindle plug in place, and checked the cable end ( VFD Drive End ) this then would indicate the he has incorrectly installed plug, on the spindle end.
    Mactec54

  11. #11
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    Re: Spindle: all 4 pins are grounded

    The Beep setting is useless here. Measure the actual resistance! Between phases and to ground/case as well.

    Cheers
    Roger

  12. #12
    Community Moderator Al_The_Man's Avatar
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    Re: Spindle: all 4 pins are grounded

    Although.. not completely useless! if it beeps from a phase to motor frame, It would mean there is current flowing (as in Diode test) so there would definitely be a problem.
    CNC, Mechatronics Integration and Custom Machine Design

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

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