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  1. #11
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    could you mount the nut on the edge of the apron for the x axis, and the front or the back for the y. That may lower the axis of the screw enough to get a reasonable one in there.

  2. #12
    Jonathan, kudos for thinking outside the box (or should i say table) i had never thought about doing it like that

    i2i, i didn't quite grasp your concept but i would certainly like to hear you elaborate on your idea, btw im only focusing on the x axis at the moment

    i had a look at some of the smaller nuts available and on average was coming up with a bill of 200 for 2 8mm nuts and 600mm of screw with 10mm screw being marginally cheaper
    compare that to 1204 ballscrews which i can get all 3 screws and nuts for 85

  3. #13
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.
    rather than having the nut between the table and the apron, you could mount it at the edge of the apron so all that has to pass between the table and the apron is the screw.

  4. #14

    I think i2i was saying put the ballnuts on the ends of the axes, instead of near the middle. That way, assuming you have room for the 16mm screw under each, you would just need to use a longer ballscrew to get the same travel. It's actually rather like how I mounted it on my lathe cross slide. There I extended the saddle with a milled block of steel, then mounted the ballnut to that to get it outside. I also had to mill a fair bit from the bed to fit the RM1204 ballscrew in.

    Edit: Didn't see post #13 before submitting this.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  5. #15
    i think its was use of the term 'apron' that was confusing me. it just makes me think of an apron on a lathe lol

    i have thought about it but i cant imagine how to implement it with much success. as far as i can imagine, i would have to mount the nut past the extremity of the table travel and at that distance i believe the mount would have tons of flex and the the overall rigidity of an overcooked supernoodle

    mounting a 1204 nut on the side of the saddle would still require machining of the table

  6. #16
    OK
    just had a brain wave


    mount the nut on the end of the table
    mount the ballscrew to the side of the saddle and use a small pulley so i can lower the motor down out of the way

    how does that sound?

  7. #17
    i2i's Avatar
    Lives in Cardiff, United Kingdom. Last Activity: 23-12-2016 Has been a member for 7-8 years. Has a total post count of 693. Received thanks 30 times, giving thanks to others 0 times.

  8. #18
    i have seen that one already, i have no issue finding 12mm ballscrews at good prices

    i am however quite stoked at the possibility of the concept i mentioned above and i must thank yourself and jonathan for giving me the idea

    cheers

  9. #19
    i did a few drawings of my concept (has anyone seen this done before?)


    the first 2 show the ball nut and a mount i designed to utilize the original leadscrew mount holes
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    i then proceeded to modify the old ballnut mount i designed into a ballscrew mount. notice how the new mounts are 0.01mm off concentric which i feel is negligible and with adjustment can be completely overcome
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    the screw mount was then further modified to allow attachment of a stepper via pulleys. it was also extended to clear the lip at the back of the knee (see second pic below)
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    and finally with a nema 23 added for good measure
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    still have to draw some pulleys, a ballscrew and a few other components. more to come soon


    so...

    any critical thoughts on this design?

  10. #20
    I would mount the stepper motor to a block of aluminium since the posts are not particularly strong, wont conduct much heat from the motor and also look like a grandfather clock. Also you might have difficulty fitting the belt/pulley between two posts? It would certainly limit your choice of ratios.
    Probably negligent, but instead of making the ballnut mount match the circular profile of the nut, I'd make the mount closer to a rectangle so it fixes to a greater area of the bed since that should be stronger.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

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