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Fixed screw/moving nut makeover of my cnc

Discussion in 'CNC Mills/Routers' started by Florian Bauereisen, Oct 28, 2016.

  1. Florian Bauereisen

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    Hi all,
    i have never particulary liked the quality of my x-axis (long axis in my case). Simply buying a new one wasn`t likely to change to the better, buying a high quality one was ... well expensive.
    A friend of mine had build a diy-cnc as well and had machined some sets of fixed screws/moving nuts for it. Lovely to watch and drool over.
    Luckiely he had made some more sets while he was at it, and so i got hold on one of these.:cool:
    Quite surprising it is not overly expensive as screw does not need to be end-machined and fixed/loose ends are simple through holes..

    the slideshow and vid show how very nice it works. Speeds had been dialed to 6500 after this vid, once run in it might be upped some more.




    If there is more questions feel free to ask

    enjoy
    greets
    flo
     
    3DMON likes this.
  2. GrayUK

    GrayUK Master
    Staff Member Moderator Builder

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    That was some cool engineering there. :D
    Would be nice to see a bit more video of it working.
    Excellent job :thumbsup:
    Gray
     
  3. Florian Bauereisen

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    Hi,
    thanks
    well i could show more vid of it moving ... but basically that would be the same all over.
    Once at work, it will be covered with my usual spoilboard thus invisible:confused:
    Just wanted to show in hope of inspiration for others...

    greets

    flo
     
    GrayUK likes this.
  4. JustinTime

    JustinTime Master
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    I wonder what the advantage is of the moving nut over the moving screw. :confused:
     
  5. GrayUK

    GrayUK Master
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    There would be no torque from the end of the screw, or potential twist in the screw, I think.
     
  6. Florian Bauereisen

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    Hi
    What Gray says is true but the biggest advantage:
    no whipping of the screw.
    My mill has 1270mm (1550 altogeher) of screw hanging free to fight gravitation.
    So accelerating from one end causes the screw to whip and that is no good at all.
    Only cure is a really big screw diameter but that causes tremendous momentum (torque requirement).
    That leads to big steppers.
    Both together prevent an agile /springy fast mill.

    Keeping the screw stationary allows for rapid acceleration and fast speeds and cheap/rel. thin screws and small steppers / servos in one package.
    As mentioned above it is not even a much more expensive solution.

    Worth thinking about if one designes a new gantry mill.

    greets

    Flo
     
    GrayUK likes this.
  7. Jestah

    Jestah Veteran
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    Thanks for the vids and inspiration! Really nice work and excited to see that this is possible as I have some 3m long screws I would love to get working.

    Could you please give us a little more info on what you used to constrain the nut? Did you mill the part your self or are they off the shelf?
     
  8. Florian Bauereisen

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    Hi Jestah,
    sorry for replying late, been tremendously busy.

    Ok, i am not a native english speaker so i hope i get your question right:

    The Pinion gets screwed to the black round thingy from one side while the nut is screwed to this black piece from the opposite side.
    The black thingy is centered in the nut housing with two simple big bearings which are held in the recesses of the housing using a big fine pitched screw and a "step up " in diameter from the other.
    Belt and pinion are of the shelf, only a little modified to suite.
    First of the pinion is center drilled to clear the big 20mm screw. and it is drilled for the M4 bolts to attache to the black thingy. The ballscrew is all original.

    The black piece could be done on a normal turning machine if it runs true and care is taken.
    Only the housing part is tricky as it would need to be absolutely precise milled to accept the two bearings precisely opposite.
    This two parts were kindly done by a friend of mine (Michael) who designed this setup.

    Hope this was understandable..

    greets

    Flo
     
    #8 Florian Bauereisen, Nov 12, 2016
    Last edited: Nov 12, 2016

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