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IndustryArena Forum > MetalWorking Machines > HURCO > Teardown Fanuc Model O servo motors in Hurco BMC-20
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  1. #1
    Join Date
    Jan 2006

    Teardown Fanuc Model O servo motors in Hurco BMC-20

    I've got 3 Fanuc Model O servo motors in a Hurco BMC-20 that need rebuilding. I can't see how to open the driven-end plate to remove the spindle and pull the driven-end bearing. I've included two slightly different views below. The black disk seems to be made of plastic, so I have been reluctant to do much to it. Thank you for your help!

  2. #2
    Join Date
    Jan 2006

    Re: Teardown Fanuc Model O servo motors in Hurco BMC-20

    I've got it disassembled, and wanted to record for posterity how to do it.

    1. The timing belt pulley is secured by a nut and lockwasher at the end of the spindle, The nut and lockwasher must be removed first.
    2. The timing belt pulley is on a taper shaft where it's been for 40+ years. Don't use a gear puller on the inboard flange of the pulley; you'll tear it up. Instead use a bearing puller plate snugly mounted next to the spindle and pull the pulley out by the small inboard hub shown in the second picture in the original post.
    3. You may or may not have a secondary oil seal with OD=25mm. If it's still in place, it's a NOK part number AB1314F0 (SB Type) and is available at Misumi https://uk.misumi-ec.com/vona2/detai...0&isReSearch=1
    4. The main oil seal (OD=78mm) is the large black rubber-coated plate, NOK part number BC3554E. Several companies make a replacement, one is available at https://www.hydraulicpumpseal.com/pr...c3554e-sc-seal It can be difficult to get out. I tried several things before resorting to drilling a small hole in the seal and screwing in a 1-lb sliding hammer.
    5. After you get the main oil seal out, life is good. There will be two internal circlips exposed, a large one that secures the bearing to the aluminum end-plate and a smaller one that secures the shaft onto the bearing. Once you pop off the 2 circlips (watch out for your eyes!) the end-plate, shaft, and bearing will come apart into 3 pieces.

    Thanks to everyone who read the thread and pondered how to help!

  3. #3
    Join Date
    Jun 2008

    Re: Teardown Fanuc Model O servo motors in Hurco BMC-20

    When you get to stripping off the back end with the encoder, there is a ring with two lugs pressed onto the shaft after the bearing. You’ll need to remove this before the bearing comes off but it’ll need to go back on in the same place it came off.
    First though, getting the encoder off can be tricky. I had best success by removing the bung on the encoder to get to the screw holding it on the shaft and taking out the M5 screw that holds the encoder on. Replace the short M5 screw with a long (M5 x 60 or about that length) screw. Undo the three screws holding the encoder body to the casting (noting the position of the tab with the notch so the encoder goes back in the same position) and then get someone to take the weight of the motor by holding the encoder body while the long M5 screw is gently tapped with a hammer to break the taper between the motor shaft and the encoder. Gently is the trick here as the glass can be broken by going at it like a madman.
    Once the encoder is off, scribe on the shaft where the two lugs are before levering off the ring.

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