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  1. #1
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    Oct 2009
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    Need some help figuring out how to attach stepper motors on my dm2400 CNC

    Hey guys Im upgrading my old Dyna Myte 2400 . Ive purchased Xylotex 4 axis kit with nema 24 426 steppers. This my first CNC build or upgrade.
    I decided to go direct drive. Im faced with the problem of how to attach the couplers to the lead screws. The old system had a 10 to 1 gear ratio. So it had a gear before the two nuts that held it on.
    Anyways I took pic of kinda before and after . What it looks like before taking the gear off the led screw and after. in the last pic there is a flat on the lead screw for the large gear but I didnt think to rotate it to take a proper picture.
    Im kind of leaning towards making my own couplers so I could attach them to the flat on the lead screw were the gear went. I just want everything to go smoothly no binding .
    I have tons of tools full machine shop so thats not a problem .


  2. #2
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    Feb 2006
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    7079
    On a small machine like that, a simple tubular coupling with a set screw on the shaft flat will work just fine. A split coupling with a couple of clamp screws will also work fine.

    Buy a spare Xylotex boards, for when yours goes up in smoke. They all seem to, at some point. The Allegro 3977 chips they use are FAR from robust, and when one goes, you have to toss the whole board.

    Regards,
    Ray L.

  3. #3
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    Do I need to keep the double nuts on there? I would guess yes but im not sure.

  4. #4
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    Can any one tell me if I need to keep the double nuts on the lead screw? I was going to design a coupler to screw onto the lead screw if not . If I have to keep them I was thinking bout making a coupler the was split and has a recessed hole in it to cover the nuts at the end of it it would have maybe some teeth . On The opposite side it would have notches for the teeth to fit in.
    I fought bout all this and I figured the last choice would make it so the was back lash in the coupler so I'm not going to go that root. A nice solid design was best so there is no chance of back lash.

  5. #5
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    Lets go over a few things.

    There was a build a few years ago here that did modify/build a coupler for direct drive. I always mistake who it was, I believe it was TravisR100 or Alex Cole? Unfortunately the links no longer work in their threads.

    Also wasnt there a thrust bearing between the gear and the casting? The coupler I referred to above was similar to a standard coupler except it was internally threaded to match the threads on the end of the leadscrew. It did have a thrust bearing between the casting and coupler. IIRC it also had the clamp feature of a split coupler in that it could be locked down once adjusted.

    I would not use a grub screw unless you want to mess up the shaft in time.

    Btw these machines are excellent and if you get or build the proper coupler type, backlash due to the coupling will be a non issue.

  6. #6
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    Quote Originally Posted by Arich0908 View Post
    Can any one tell me if I need to keep the double nuts on the lead screw? I was going to design a coupler to screw onto the lead screw if not . If I have to keep them I was thinking bout making a coupler the was split and has a recessed hole in it to cover the nuts at the end of it it would have maybe some teeth . On The opposite side it would have notches for the teeth to fit in.
    I fought bout all this and I figured the last choice would make it so the was back lash in the coupler so I'm not going to go that root. A nice solid design was best so there is no chance of back lash.
    A solid coupling between the motor and screw is a BAD idea! Unless you manage to get the two shafts absolutely, perfectly aligned, in all three dimensions, it WILL eventually snap the shaft on the motor, through fatigue. Even a mis-alignment small enough that you won't be able to detect it, will eventually fatigue the motor shaft. There are numerous kinds of shaft coupling that allow slight misalignment, with no backlash.

    Regards,
    Ray L.

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