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IndustryArena Forum > MetalWorking Machines > Milltronics > Z axis servo brake failure
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  1. #1
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    Join Date
    Jun 2013
    Posts
    16

    Z axis servo brake failure

    A few weeks ago my Z axis stopped moving, the brake was no longer being released. After probing wires I determined that the windings inside the brake had failed as it was an open circuit.

    Sorry I didn't take any pictures of the servo disassembly but the brake is bolted to the mounting plate of the servo motor. Remove the 3 allen head screws in the center circle and the 4 5/16 head nyloc nuts and pull the bottom plate off. Then use a small gear puller to pull the bearing as it's a slight press fit onto the shaft and then the brake will drop out.

    Since the bobbin for the windings is glued into the brake I had to machine a new one from delrin.

    Attachment 450312

    Then I used my little CNC lathe to wind the 35g wire because I could run it for a set time at a consistent speed to count the windings. My rough counting of the windings on the original was 2800 wraps, but my calculations said I needed closer to 3800 wraps to get the 13w consumption at 90v which should yield 623ohm. I measured the one on my other mill at 575ohm so there is some wiggle room.

    Attachment 450314

    I ended up with around 3600 wraps as I stopped early to leave room on the bobbin for the leads which ended up at 585ohm. Maybe 36g wire would have been better but I measured the original wire at 0.0061" which is 35g.

    Attachment 450316

    All glued into place.

    Attachment 450318

  2. #2
    Junior Member
    Join Date
    Jun 2010
    Posts
    127

    Re: Z axis servo brake failure

    Congratulation's, Good write up

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