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Thread: DIY CNC machine on the cheap!

  1. #121
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    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by skrubol View Post
    How come the Z axis rails are so far away from the carriage? Those little threaded rods are going to flex a LOT at that length. You will need to add a lot of triangulated bracing if you want to get decent results cutting anything harder than styrofoam.
    That's to provide room for the Z-axis assembly although they are much further than necessary in the photo. I adjusted them later (more photos will be uploaded shortly).

    I'll try to cut as slow as possible for my first cuts but if the flexing is more than I can bear, then I'll switch out the threaded rods for 8mm ones.
    The idea is to use this first crude set up to cut some neater more accurate MDF pieces for a smaller Z - axis assembly. If this can just hold out long enough for that, I'll be golden.

    Quote Originally Posted by skrubol View Post
    The problem with a sealed box and no vacuum (or compressed air,) is that the chips you're cutting will just pile up on what you're cutting and cause lots of problems if they aren't cleared away frequently. When cutting wood you can easily start a fire.
    I'm still not set on the sealed box. I know chips will build up on the rails and probably bind up the axes if nothing is done about it for a long time on long jobs; perhaps I could attach a small fan to one end of the box and a vent to the other to direct the dust outside the building. I'll keep thinking in that regard.



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    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by Dec0y View Post
    As many have said your design will be plagued with lots of movement.
    It appears you are fixed on your design but I urge you to reconsider your design
    I would recommend you consider a fixed gantry moving bed or high fixed walls for your Y axis that a low gantry rides on.

    take alook at this video

    Thanks for the suggestion but I've come a long way to do anything about it. I'm fully aware of the short comings of a moving gantry CNC and if I had to do it all over again, I'd probably do a fixed gantry. I'll see how it goes.
    A second machine won't be long after this guy is finished.



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    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by aarggh View Post
    Aside from the serious trouble you'll have with the machine flexing in every direction in use, relying on a dust enclosure will simply clog up every single part of the machine that moves with dust, which will make things run roughly, and with more flex when the bearings are riding on clumps of built up dust. Wherever possible you need to remove dust at the source, in this case at the cutter.
    I have considered that and actually, one way around the dust build up on the rails would be tiny brushes mounted on the moving assemblies to constantly bush the dust off, but I highly doubt it would be very effective. I'll keep thinking.

    Quote Originally Posted by aarggh View Post
    Water cooled spindles are very quiet, and will be the most ideal solution for machining indoors, and as you'll have dust problems, they won't be affected by the dust like an air cooled one would be, which would be noisier anyway.
    Water cooled spindles are completely out of the question for this first machine. I want to make it as cheap and easy as possible. Once, I've got it up and running, I'll tackle the various problems it will have one at a time starting with the most urgent. It will be very exciting to see what issues will manifeste from blunders I made designing and building the machine.... can't wait!!!

    Mean while, I got all the electronics I'll need. I've decided an Arduino will run the show with A4988's on a shield.
    For the spindle, I'm going with the flimsy 775 motor and ER11 collects!



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    Default Re: DIY CNC machine on the cheap!

    Z axis assembly.

    Sent from my SM-J250F using Tapatalk



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    Default Re: DIY CNC machine on the cheap!

    Hi Isaac - Your design is coming along well. Bolting through a SHS section with a single bolt means you can't torque the bolt up very tight as you will crush the section. Think about using channel vs SHS sop you can bolt up connections hard to each other. Or drill an oversize hole in the SHS so the bolt can bear on one side only... Your machine stiffness depends on its connections and these depend on friction which depend on max preload of the bolt. Keep at it... Peter



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    Default Re: DIY CNC machine on the cheap!

    I'm not surprised that the next machine is already under consideration,that tends to be the normal way.Every lesson learned from building this one will be valuable for that one.In the meantime you will be able to use this one and keep learning while making some parts of whatever needs making.



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    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by peteeng View Post
    Hi Isaac - Your design is coming along well. Bolting through a SHS section with a single bolt means you can't torque the bolt up very tight as you will crush the section. Think about using channel vs SHS sop you can bolt up connections hard to each other. Or drill an oversize hole in the SHS so the bolt can bear on one side only... Your machine stiffness depends on its connections and these depend on friction which depend on max preload of the bolt. Keep at it... Peter
    Thanks Peter,
    I actually switched from the SHS to the steel angle because of that. Well that and the fact that the quality of SHS you get here is appalling,making it hard to alighn holes on other side of it. The steel angle has served me very well thus far, I only have to drill a single hole and that's it. Thanks for the encouragement.



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    Default Re: DIY CNC machine on the cheap!

    Quote Originally Posted by routalot View Post
    I'm not surprised that the next machine is already under consideration,that tends to be the normal way.Every lesson learned from building this one will be valuable for that one.In the meantime you will be able to use this one and keep learning while making some parts of whatever needs making.
    Hello routalot!!! Hope all is well.

    Yes, I'm very eager to get this one up and running and getting cutting for my next machine! I guess I could say I've caught the "CNC-bug". First thing will be to make improvements to the Y and Z - axes. I'll make a compact design out of MDF which will probably get me a few extra inches of work area in the X direction. Movement is really smooth and everything is surprisingly rigid. I'm a little concerned that the spindle will hang a little too far ahead of the Y - axis, but that will be short-lived. It's indeed going to be a steep learning curve. For the start, I'll probably use easel although I really haven't decided what I'll use later once I've gained some experience.

    Regards.



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DIY CNC machine on the cheap!

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