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Thread: Building my first JGRO based on 2004 plan

  1. #13
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    Default Re: Building my first JGRO based on 2004 plan

    I am near completion on my gantry assembly. It's a very satisfying point in the build. The box is mostly finished, except I need to cut one more piece for the gantry front. I have the rear brace as a solid board (haven't cut the hole in it) and have the sides, bottom, blocks, and Y bearing assemblies all joined up. I just need to get to the store and pick up four 1/4-20 3" hex-head bolts as I'm making do with 2-1/2" bolts right now. The whole thing is standing atop a few pieces of scrap wood so that the angle bolts of the Y bearing assemblies don't take too much strain.
    Building my first JGRO based on 2004 plan-img_0923b-copy-jpg

    In my prior post I'd said I wasn't sure why someone would use OD 0.219 as opposed to 0.203 for the #10-24 thru-holes, and now I think I see why. I'm about to assemble the anti-backlash nut for the X axis (gantry) and while everything looks like it lined up properly, having some slop in the placement of the holes will be a good thing.

    For the Z axis assembly, the ABL nut could slip a bit within the routed channels of the Z assembly. But for the X axis, you have to make sure the pipe placements with respect to the center point of the holes in the gantry and hole for the the lead screw are all nicely aligned, and if the ABL nut were to be in a firmly fixed position, it wouldn't allow for any inaccuracy in the other pieces.

    Here's how the X axis nut support is lining up currently. It's pretty good, but hard to tell exactly how accurate things are.
    Building my first JGRO based on 2004 plan-img_0924c-jpg

    I'm thinking a better design would have been to have made larger through-holes in the X Axis Nut Support (cnc_dtl37), and instead of having 4x OD 0.150 holes for holding the ABL nut, make those through-holes, too. Then, use longer #10-24 screws, and let them slip through to a washer/lockwasher/nut. That way, the assembly steps would be:
    - assemble the Z axis and gantry box
    - attach the Z axis assembly to the pipes on the gantry assembly, and align and tighten them
    - drill the holes of the ABL nut
    - tap the hole of the plastic so it matches your lead screw type
    - thread the plastic onto the lead screw (far enough in so that can be on the interior of the gantry box)
    - attach both ends of the lead screw -- motor end and flange bearing end
    - slide the Z axis assembly across the tubes rotate the lead screw manually until the ABL nut meets up with the X axis nut support.
    - at this point, if the ABL nut mounting holes don't align with the X axis nut support holes, it's too messed up anyway. But if they do align, slip through the #10-24's and bolt them on, using lock washers so things don't get loose.

    The good news, I suppose, is that the current design starts with a small hole for directly mounting the ABL nut to the X axis nut support, so if that doesn't work, I can drill those out and make larger holes. Or just rebuild that piece.

    I do feel validated in my build-from-the-inside-out approach. Where in the Z axis I had problems with alignment, this time I joined up everything and pre-measured the pipe distances before cutting the pipe holes in the gantry sides. They ended up measuring 8.8" apart, not 9", and so I measured outward 4.4" from the center hole, and then drilled the pipe holes. I also was careful to drill both sides at once, face-to-opposite-face, when making the pilot holes. I know, probably seems obvious to experienced woodworkers, but that helped minimize error in hole placement, compared to measuring/punching/drilling holes in each gantry side independently.

    So here's my question for you JGRO experienced builders... Where should lock washers go on this thing? Seems to me that in many places, I'm putting a 1/4-20 through a hole and bolting it on the other side, sometimes with a flat washer. But wouldn't it make more sense to have lock washers in lots of places, especially since the whole system will experience a lot of vibration?

    A separate question: what's with the holes in the front of the left and right gantry side panels? They don't appear to serve any purpose, but right now I'm thinking that they just make for convenient handles so you can carry the gantry around.



  2. #14
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    Default Re: Building my first JGRO based on 2004 plan

    Sorry a bit late for the party.

    Never needed lock washers on mine. The compression of the bolts against the MDF held them in fine. The only bolts that came lose was on the adjustment blocks and is why there are two. The holes on the sides of the gantry are for the screw for the outer lower adjustment blocks on your Z to pass through.

    Even though outdated the JGRO is a fun build. I learned a ton with mine.



  3. #15
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    Default Re: Building my first JGRO based on 2004 plan

    Are you still working on this?



  4. #16
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    Default Re: Building my first JGRO based on 2004 plan

    Still working on it, but slow going for the past few months. Where I am now: got one end of the Y axis glued up and marked for cutting. I want to cut another piece just like it for the other end, and drill through the holes of the first into the second so things line up properly.

    I also headed down the path of building a box for the electronics, and will post pics of that the next time I have time to post here. I took a discarded old DVR from the dump bins, and pulled it apart. It effectively became my first attempt at case modding, and the newbyness shows, but it's working. I chose that box because it had enough room for the power supply and Gecko. I actually left the original DVR power supply in, in case I'd want to reuse its original front panel buttons and LEDs, though I'm not sure if I'll be able to do that since it has a 20-pin flat ribbon cable that is hard to a breadboard-style assembly -- so that's another future project. I ended up getting mostly done with that, but want a more solid power inlet. Right now it's doing the very uncool thing of just pushing a 3-prong power cable through a hole in the back, and having its individual wires go to the power supply's terminals, so I'll be looking to a local high school wiz kid for mentorship since he's done this kind of thing properly multiple times before.

    So in the end, no 3rd axis yet, and thus no initial cut yet. But it's summer now, so maybe I will put some cycles on it again soon.



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    Default Re: Building my first JGRO based on 2004 plan

    For me the winter is when I like projects like this. We camp every weekend during the summer so not much free time. The wife lets me do stuff like this if I use the money from my part time job and this summer is looking like I will have lots of hours so might as well start learning and saving now.



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    Default Re: Building my first JGRO based on 2004 plan

    I realize you are well into the project, but thought I would share a link to my JGRO build and updates to the machine since. You can find them at JGRO CNC Router. I really like my JGRO even though there were times we struggled to get along. My only issue with it has been rigidity, But I suppose that is another story. Hope there is something there that might help you out.

    Joe



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    Default Re: Building my first JGRO based on 2004 plan

    Hey DaveJGRO,

    I know its been a while since you lasted posted. Any updates on your build? I'm using the same plan for jrgo cnc and I will be referring to your post frequently.



  8. #20
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    Default Re: Building my first JGRO based on 2004 plan

    Nice clean job so far....:O)

    Don't Give Up The Ship !!!


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Building my first JGRO based on 2004 plan

Building my first JGRO based on 2004 plan