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  1. #11
    Thanks Gerry, I will listen to Jonathan is saying and I will keep working on a new design and then ask for help in choosing screws, motors and drives once I've sorted how to have part of the bed removable so I can add a 4th axis at a later date. Still looking at the build logs and other stuff to aid in the overall design.

  2. #12
    Hi everyone, I've had a play around with the design and changed the orientation round. It won't be a problem working over the side rails and as Jazz said it will make the machine stronger. Going to order the rails from china as I don't mind waiting a few weeks as I have lot of other things to do.

    I would like your views on the ball screws to use ? so I can order these as well. I'm mainly going to be cutting and engraving wood and phenolic (laminate) and some plastics. Next will be the motors and drivers but not in a rush at the moment due to a lack of funds.

    Your help will be much appreciated in getting the right ball screws.
    TiA Mike

    Click image for larger version. 

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  3. #13
    Quote Originally Posted by longy View Post
    Your help will be much appreciated in getting the right ball screws.
    You want 10mm pitch for X & Y axis 5mm for Z axis. Now personally I'd go for 20mm diameter at this length and sacrifice a little acceleration/speed in favor of reducing potential for whip compared to 16mm diameter.

    Now the ratio I was talking about before comes from how you attach the motors to the ballscrews.? I always connect the ballscrews to the motors with Timing belts & pulleys. Doing this reduces affects of resonance on the motors and gives smoother running motors but it also allows a Ratio to be applied if needed.
    This ratio can be applied both ways to either give Higher resolution and boost torque but at the cost of Speed or increase speed at the expense of torque and Resolution. Now in practice 10mm pitch with a 1:1 ratio works great for anything but fine engraving or work that requires high resolution. But if needed then a quick pulley change to 2:1 and you instanly get higher resolution.!

    Can I also suggest you price up Profiled linear rails from Chai before buying the Round type.? . . . I think you may get a pleasant surprise.!
    Even the cheap range of profiled linear rails blows the round type out the water and the slight difference is money well spent.
    Last edited by JAZZCNC; 14-04-2014 at 09:11 PM.

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  5. #14
    Thanks very much for your input JAZZCNC, I'm busy pricing up 2010 end machined ball screws and getting even more confused with this end machining terms like " MPF, IDE, FUS, WFR, WWF, DGK, MPH" no idea what it means. Could I use 2010 on the X axis (1500) and drop down to 1610 for the Y axis ? Would this cause problem setting the machine up ?

    As for the profiled linear rails I can't find the lengths I need on ebay and uk supplier prices put it well out of my limited budget, looks as if I will have to go with supported round rails.


  6. #15
    No need to get confuddled it's not rocket science really. The letters will correspond the Ballnut type. You just want standard flanged ballnut.

    Regards dropping the diameter for Y axis then it won't affect setting up at all. What the larger diameter tends to do is reduce the acceleration and overall rapid speed you can tune the motors to, inertia and all that, but in practice with 10mm pitch and slaved 3Nm motors you have more than enough power in reserve and will still get perfectly acceptable feeds/accel that excede what you'll ever need for cutting. Whip is something you want to avoid at all costs and your in the region of where it can happen and for the little difference I won't take the risk.

    Regards the Profiled linear rail and Ballscrews for that matter then Give Chai at lineramotionbearings a email with the sizes you need, give him total length of screws including the machining, ask for them machined and he will give you a price.
    I don't think he shows profiled linear rails on his Ebay site but he does supply them, I've had loads of them now and they are fine.

    I'll PM you his email.
    Last edited by JAZZCNC; 15-04-2014 at 12:54 PM.

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  8. #16
    Thanks JAZZCNC, I'm easily confuddled these days I just put it down to my age LOL. I'll go with the 20mm ball screws for the longer X axis so it reduces any whip in the ball screws. This might be a daft question but how do you work out the length for the ball screws ? against the linear rail travel length taking into account for the mounting blocks BK15 / BF15 and the ball nut and mount. Thanks Dean for the PM very much appreciated.
    Last edited by longy; 15-04-2014 at 02:26 PM. Reason: ball screw lenght question

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