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  1. #1
    Hi all.

    As anybody a strong opinion on whether or not to change the standard drive shafts on my cnc converted milling machine to Ballsrews or leave the originals in.

    Can anyone recommend which Stepper Motor Drive couplings are best for CNC application.

    Regards

    Ray

  2. #2
    I'm dithering about with a Warco WM16 mill which I plan to convert to CNC but was planning on leaving the standard lead screws in and seeing how it performs. If it turns out to be crap, then I'll look at anti-backlash nuts, followed by ball screws. Ball screws cost about 5x the standard acme lead screws, but are they *really* 5x better?

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  4. #3
    C_Bubba's Avatar
    Lives in LaGrange, GA USA, United States. Last Activity: 12 Hours Ago Has been a member for 7-8 years. Has a total post count of 77. Received thanks 11 times, giving thanks to others 1 times.
    All I can say is when I converted my RF-31 back about 2000, I left the original lead screws in and within about 2 months (even with a one shot oiler), I had worn the bronze nut out enough to "walk" it down the screw with no rotational movement of either the screw or nut.
    Worth 5x, Yep!

    My thoughts anyway.
    Last edited by C_Bubba; 19-05-2013 at 07:12 PM. Reason: fat fingers some data
    Art

    AKA Country Bubba
    (Older than Dirt)

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  6. #4
    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.
    ballscrews all the way...worth 20 times the cost of the leadscrews.

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  8. #5
    Leadscrews are OK to get started, as it's generally very easy to just add motors and use the original screws. You can probably then change to ballscrews without wasting much if any money on parts. However, you'll soon find that backlash, low efficiency and wear (to name but a few) make the overall machine much less useful than it could be.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

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  10. #6
    ballscrews all the way...worth 20 times the cost of the leadscrews.
    What he said..

    You can easily get rid of backlash in lead screws by tensioning (or compressing) two nuts together but the resultant friction is often more of a problem than the backlash. My little mill has has this type of anti-backlash and I can get pretty much zero backlash but the friction is so high it is difficult to turn the hand wheel and impossible to get smooth motion. as already pointed out this will also result in the screw wearing out quickly.

    The halfway house is to use brass nuts and a hydraulic tensioning system to self adjust for the wear and then replace the nuts as when they totally wear out. but by the time you set that up it is probably easier and cheaper to get a ball screw.

    Don't be tempted to use delrin, been there done that and it has no place in milling machine. I've learnt from my mistakes and I'm getting ball screws for the next one.

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  12. #7
    Done a few WM16's and one thing to bear in mind is that some convert easily and some don't.
    The stumbling block is the bed in the middle, the casting when being cast, sags and make the gap tighter in the middle.
    No problem with the top, that's machined so no sag. From the ones I have done it's 50/50 if a ballnut clears.

    So worst scenerio is to get someone with a big mill to take a lick out or angle grind a clearance grrove.

    WM14 are usually OK, I haven't come across a bad one but WM 18's 'always' need machining
    John S -

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  14. #8
    Many Thanks, Any thoughts on the couplings?

    Ray

  15. #9
    Oldhams, they are the only non backlash coupling that works CORRECTLY in two planes.
    All the others are fück ups.
    John S -

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  17. #10
    Quote Originally Posted by manofgresley View Post
    As anybody a strong opinion on whether or not to change the standard drive shafts on my cnc converted milling machine to Ballsrews or leave the originals in.
    Clearly, yes some people have strong opinions.

    Personally I think it depends on what you intend to use the machins for. I am using Delrin anti backlash nuts on my converted Chinese mill but then it is only a toy for learning and occasional use in model engineering. I have 1 thou backlash on both X and Y axes and it gives very little friction at that setting.

    If you are going to use the mill every day for production purposes there is no question that ballscrews are necessary.

    ... just my 2 centimes worth.

    Russell.

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