4' x 4' possible?

This topic contains 15 replies, has 6 voices, and was last updated by  Curt 2 years ago.

Viewing 16 posts - 1 through 16 (of 16 total)
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  • #3062

    innkeeper
    Participant

    Id like to build a usable size of 4×4′ ( x and y ~5′ conduit) however I am worried about the possibility of the EMT tubing flexing when using a Dewalt DW660 type spindle option

    Has anyone built and using a MPCNC of this size with a Dewalt, and are there any issues?

    I can see how to easily re-enforce the outer frame, but threes no way to add additional support on the X and Y conduit that connects to the Z axis and am worried about that flex and even bending.

    #3077

    Ryan
    Keymaster

    I am moving in a few weeks. I hope to throw together a really large one and see how it goes when I get there, before I get to settled.

    I think if you support the outer rails you will be okay. Just make it as small as you can. Every inch counts at that size.

    #3085

    innkeeper
    Participant

    it is unfortunate the current design dosn’t lend itself to add additional support to stiffen the inner x or y rails that attach the Z axsis. if one of the z Aziz rollers that attach the x or y axsis were open either above or below if you could add support to stiffen it (think I beam type structure). In theory, it could then be as large as you could dream up. To start i’ll probably build a 3×3 outer dimension just to get the electronics going and test a support design for the outer rails.

    #3097

    Ryan
    Keymaster

    Before you start designing improvements, try out the current design. There are so many things to learn about CNC having a “smaller” one to start with is probably a good idea.

    I am always trying to come up with ways to improve this. Right now rigidity isn’t my main concern, its actually a single machine that works with multiple size rails. So instead of adding pipes, bearings, extra hardware for rigidity you can just get a larger diameter. It will also make this Australia friendly. They seem to be the only country that can’t get 23.5mm or 25mm pipes.

    #3175

    alexpewpew
    Participant

    Here is a video of my 4×4 (pipe length) machine I just finished. Flex in the pipes seems to be unnoticeable, but during my first cut one of the steppers skipped steps due to a loose belt. Getting those right seems to be a bigger challange than rigidity.

    #3176

    Ryan
    Keymaster

    I wanna see it, but there is no link!?
    Zip ties aren’t working for you?

    #3179

    alexpewpew
    Participant

    her is one video https://www.youtube.com/watch?v=0bFK9dD4zVo and here is the other https://www.youtube.com/watch?v=jx7bP04f8M8 . I went for the corner brackets that add on, if i were to reprint the pieces i think i would edit the corners to include those so it prints as one piece. I like the easy way to adjust tension so I can figure out how tight I can get with out over doing it. With a smaller frame I don’t think I would need the corner brackets.

    Thank you so much for the design!

    #3180

    Ryan
    Keymaster

    Looks great, something a little different. I love to see these videos. Thank you for making it. I added it to the website.

    …I have the same screwgun…

    #3190

    Bluff Chuffer
    Participant

    Hi,

    I figure that the timber sides shown in the two video’s above could be brought right up to contact with the frame tubes, thereby supporting them The roller design allows for this since the bottom of the tube is not used for a bearing runner. The timber must be thin enough though.

    #3191

    alexpewpew
    Participant

    You could support the tube with the wood but I don’t believe that it is necessary. The tubes feel rigid at this length. I think the bigger issue is the drive belts having proper tension.

    #3192

    Ryan
    Keymaster

    I’m not seeing how tension is an issue. I used zip ties for this very reason. If it is too loose just click it a notch or two until it is right. Should only take a few minutes?

    I had a 3D printer where you had to cram the belt into a ribbed notch thing and that was next to impossible to get right. the zip ties are a cinch. hahahah I crack myself up

    #3193

    Ryan
    Keymaster

    Never mind, I see you decided not to use the zip ties….

    #3223

    innkeeper
    Participant

    I saw an interesting setup at maker faire today, for a completely different machine then a cnc machine.., but with a similar setup to the MPCNC……what someone did was lay the belt down onto a piece of aluminum so the belt was sandwiched between the rollers and the aluminum. this took some tension off the longer part of the belt so stretching was less of an issue as it moved.. I thought it was an ingenious design element, though might wear the belt faster..we could do something similar with another piece of conduit…..not only would it do that, but add a little rigidity/support on those long runs.

    #3228

    Ryan
    Keymaster

    Interesting, did you get any pictures?

    I’m not sure if I’m understanding it right, like a rack and pinion. the pulley rides on the belt? If that is it, belt teeth up is bad because it traps dirt causing wear to the belt as the pulley grinds the debis into it, and tooth engagement. Using these small pulleys you need to wrap the belt around and engage as many teeth as possible or you you get the possibility of slipping.

    I need to catch the next maker faire.

    #4981

    Gabriel
    Participant

    Hi This my first post here. Greetings from Poland. Great design. Thank you for all your work.

    I think innkeeper talks about setup which i see on the oxcnc machine from openbuilds where one of the belts is glued to aluminum rail, and second one is routed like in your design.. They do this for bigger machines to remove belt stretching.
    Here is video which explains everything

    #4984

    Curt
    Participant

    the dual belt is an impressive concept!

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