2nd build - For a friend - Page 27


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  1. #313
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    Default Re: 2nd build - For a friend

    Quote Originally Posted by JeremyFXDWG View Post
    I think i just figured it out. I was looking at the below diagram and could not put it together initially but Input A and B are defined by software so I would assign say direction to A and Step to B. Then it is just normal wiring like a stepper to the MB2 into the respective Step and direction terminals.

    Are you using the enable signal with the MB2?

    Attachment 362050
    Yes. The enable circuit on my friends machine runs through the E stop switch.

    Sent from my Pixel XL using Tapatalk



  2. #314
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    Default Re: 2nd build - For a friend

    awesome.. thank you!

    I am going to try and diagram all this out and post it up to help others too as it is a good learning process for me.



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    Default Re: 2nd build - For a friend

    Hi, I just found this from the newletter, sorry I don't have time to read 22 pages of comments.

    Looks very serious. Excellent construction. One thing I doubt is whether you will be able to control movement to the 5 thou' accuracy you want on hard materials with rack and pinion drives. Are you using some kind of anti-backlash mechanism?

    I'm building a similar machine but about half the X,Y work area you have used. I chose ballscrew drives to ensure minimal movement error. They are a little slow on full axis movement: 22" of gantry takes about 7s , the best I have been able to do. Certainly usable.



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    Default Re: 2nd build - For a friend

    I don't know, I've never checked its backlash. I've never had to. I've cut out pockets for parts in aluminum and it seems very accurate. I.e. an 80mm pocket for an 80mm part is a snug fit. Everyone seems to make the comment that rack and pinion drives are subject to backlash. On 2 machines I've used the R&P products from Moore gear and CNC Router Parts and the first one had no backlash and I never saw a reason to check this one. Ballscrews are certainly ideal, but I wanted this machine to be fast. R&P was a better fit in this case.

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    Default Re: 2nd build - For a friend

    I just mentioned that since it was one of your stated design goals. You can get away with a lot on ali but hardwoods like oak will push back.

    I have cut parts in ali on a cheap chinese CNC router that you could bend all over the place by hand. It came out alright with light cuts. It's not a good guide for what happens with tougher materials. I am hoping to work mild steel with my machine so I've opted for ball screws.

    Getting enough rigidity is a problem using linear bearing type construction particularly on the Z axis and of course it all adds to any backlash. It is worth checking backlash the resistance to side load on each axis as you go along. There will a lot less chance to make modifications once it's built.

    I agree R&P is more robust and less prone to machining dust. I'm planning to add extra dust protection to my ball screws to prevent ingression of foreign particles into the bearings.That's definitely a downside.

    Last edited by reg.miller; 06-15-2017 at 01:23 AM.


  6. #318
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    Default Re: 2nd build - For a friend

    You can get away with a lot on ali but hardwoods like oak will push back.

    Oak is nowhere near as hard as aluminum. Any wood is much easier to cut than aluminum.

    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


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2nd build - For a friend
2nd build - For a friend