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The RAT. A form ply and aluminium hybrid.

Discussion in 'CNC Mills/Routers' started by Slewratesarego, Oct 1, 2014.

  1. Slewratesarego

    Slewratesarego Journeyman
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    Slewratesarego published a new build:

    Read more about this build...
     
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  2. Serge E.

    Serge E. Master
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    Interesting concept... looking forward to details.
     
  3. Slewratesarego

    Slewratesarego Journeyman
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    Thanks Serge. Just waiting on the router bits now and I'll start cutting it out. Can't wait!
    The next step will be to purchase all the electronics. Thinking of going along the lines of a Gecko G540 and nema 23s for the X and Y and a 17 for the Z.......?
     
  4. Jestah

    Jestah Veteran
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    I was really impressed by the formply gantry I saw built in NZ. Really nice balance between weight and stiffness.

    Looking forward to seeing more about your build!
     
  5. Slewratesarego

    Slewratesarego Journeyman
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    Thanks Jestah! Got any pictures of the NZ gantry?
    Using 4 bits of 1m 20x40mm with a bit of form ply to get a little more height , all sandwiched between two plates of 3mm aluminium, bolted every 100mm or so.
     
    #5 Slewratesarego, Oct 2, 2014
    Last edited: Oct 2, 2014
  6. Jestah

    Jestah Veteran
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    I wish i did but the builder requested that I not take any photos while I was installing a Mach3 controller to his build.

    The build made good use of tabs locking into slots. This located the parts well and locked every together once it was assembled. Much like this:

    http://kavasmlikon.wordpress.com/2012/11/21/laser-cut-enclosure-box-for-your-rfid-project/

    I forgot how he screwed it together as I am not sure how well the end grain of the ply will hold a screw but I don't think he used a captive nut like the link above.
     
  7. Slewratesarego

    Slewratesarego Journeyman
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    Thanks Jestah! I plan on using cross dowels to join the timber in conjunction with the slotting mentioned above.
     
  8. Mark Carew

    Mark Carew OpenBuilds Team
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    Well done @Slewratesarego ! Looks like a work of art and built very strong. Looking forward to seeing how she cuts.
    Keep up the good work.
    Mark
     
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  9. GrayUK

    GrayUK Master
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    Looks great Slew. :thumbsup:
    So when are you going to carve some pattern or design, into those terrific pieces of ply you've used? :ROFL:

    Gray
     
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  10. Slewratesarego

    Slewratesarego Journeyman
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    Thanks guys. Yeah, me too Mark. Funny you should mention that it looks like a work of art, my sister said almost the same thing when I told her I was designing a cnc machine. She said it would be a work of art. :)
    So, what are the pros and cons of having a lot of mass in the gantry? I'll try and weigh it some time soon.
    Well Gray, as soon as I get it up and running, I'll carve a logo into the back part of the gantry brace. ;)
     
    #10 Slewratesarego, Oct 21, 2014
    Last edited: Oct 21, 2014
  11. Mark Carew

    Mark Carew OpenBuilds Team
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    I would say keep building and see how it works. You will be moving the gantry slowly to do cuts anyway so I never see a reason to speed up the CNC for heavy cutting work. Little at a time helps to save ware and tear on the machine as well.
     
  12. Slewratesarego

    Slewratesarego Journeyman
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    Thanks Mark. Just about to start putting the base together. :)
     
  13. Slewratesarego

    Slewratesarego Journeyman
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    Anyone out there know what the exact distance should be between two solid V wheels for them to sit perfectly in a bit of horizontal 2040 for example? My callipers have been lying to me.
     
  14. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    20mm minus one wheel thickness measured at the bearings. Now all you have to do is figure out what one wheel thickness is at the bearings. (Good luck getting any two wheels to agree.)
     
  15. Slewratesarego

    Slewratesarego Journeyman
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    Thanks @Rick 2.0, I understand all that. So what you are saying is that not all wheels are the same thickness?
     
  16. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    In theory they should be but I never can seem to get the same measurement twice. I just pulled four from an assembly I've been meaning to take apart and got 10.95, 10.96, 11.01, and 11.04. Theoretically you should be using the 9mm spacer between the wheels but if you are requiring absolute precision you will need to be doing some balancing of the thicknesses.
     
  17. Slewratesarego

    Slewratesarego Journeyman
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    Hmmm, well that explains it then. I'm running four pairs on the to top and bottom of the gantry carriage and they don't seem to line up perfectly. Grrr, guess it's going to take a while to get them all to sit right. The search for M5 shims begins......
     
  18. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    Really shouldn't need shims. Just measure all you have to work with and pair up one each of a less than 11.0 and a greater than 11.0 attempting to get all pairs as close to 22.0 as possible. Then just put all the thinner ones along one groove and the thicker ones along the other.
     
  19. Slewratesarego

    Slewratesarego Journeyman
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    I would if I had a decent set of callipers. :rolleyes:
    That'll have to be my next purchase after all the other stuff.:) Thanks again @Rick 2.0
     
  20. mike125

    mike125 Well-Known
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    Looks good, so far!
     
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  21. SlyClockWerkz

    SlyClockWerkz Veteran
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    This is very good looking, I'm glad some people are also looking into a larger/beefier gantry design. I think its required if you want a 750mm+ x gantry
     
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  22. Serge E.

    Serge E. Master
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    Going for a 1500mm X gantry with some issues, I would say yes. At least have the back 20x60 (third, some suggest as 'optional') needs to be horizontal rather than vertical like the other two. But that requires modifying the Y plates. That requires a CNC machine, which I don't have yet as I'm building it. So it might not be a bad idea to start with a smaller design, even if just for having a machine to do parts for the bigger design(s).
     
  23. GrayUK

    GrayUK Master
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    I think you might be right Serge regarding the size, but it would break my heart to cut up a valuable piece of V Slot. It's not like you can just pop down the road to get another length is it? :cry:

    Plan? Get it built, then improve it. :thumbsup:

    There should be a Tag line at the very beginning of this site saying:

    "You ain't gonna get it right the first time, so build a small one first!" :banghead:

    Gray
     
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  24. Serge E.

    Serge E. Master
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    Well said. In my case, I figured the cost was mostly made up of everything but the V-slot, so might as well go for the big one right off the bat. :duh:

    The trick would of been to buy a few extra length of V-slot to make a babyOX - scaled version of the big 'one' :rolleyes:

    All that is needed is 1 extra 20x60 1500mm cut in three equal parts for the X beams, 1 extra 20x80 1000mm cut in two equal parts for the Y beams. The 20x40 for the base can hang long during the experience with a babyOX, unless one is ready to spring an extra 15$ or so to cut 1 extra 1000mm into two parts equal to the X beams. Pre-cut 500mm length are now available (when in stock) from OBPS.

    No need to buy everything else in double ...

    In any case, its only about 50$ of extra material (reuse the screws and rest) without the 20x40 or 65$ with it. It represents a small fraction of the total cost of a large OX. One could even resale those bits of V-slots for the next guy wanting to give it a go. Kind of pay it forward, get an other person hooked on DIY CNC mill/router. :rolleyes:
     
  25. JustinTime

    JustinTime Master
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    I think only the X axis has to be cut, if you're going to make a small machine first. Let the Y be as long as you plan for the full size, it's mounted securely.
     
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  26. GrayUK

    GrayUK Master
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    Very True

    Gray
     
  27. Slewratesarego

    Slewratesarego Journeyman
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    Relatively speaking though, V slot is cheap. Just double up every where you can. Hence the four bits of 2040 some vertical, some horizontal, all bolted together with a 3mm al plate either side. Not entirely sure but I'd like to think that this would be a lot stronger than two bits of 2060.:)
     
  28. Serge E.

    Serge E. Master
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    So true. So you could get away with just cutting one extra length of 20x60.

    We forgot some GT3 which could be 'wasted' ... depending on how it's clamped down on the babyOX. At worse, just a couple of feet will be wasted anyways.
     
  29. FRIDGE

    FRIDGE Well-Known
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    Weight should be fine for those nema 23's .... my last cnc i constructed out of 150mm 'c' channel (metal -- shelving i utilised) ... can't remember the exact measurements but i'm sure the gantry was wider than 1.8 metres , x axis was more than 2.5 metres .... ran it on a belt system similiar to the v-belt system .....here's a you tube link ...
     
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  30. Slewratesarego

    Slewratesarego Journeyman
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    Thanks FRIDGE, any hints on belt tensioning and getting the alignment right? Things to watch out for to negate slippage?

    My build has slowed down to snails pace, with a whole a lot of hurry up and wait happening right now. The slow boat is truly a slow boat.
    Waiting on one last piece before I begin the process of calibrating and finally watching it complete a job or even draw a pretty picture.
    I should fire the project manager, what with how long it's all taking. Oh whoops, that's me. :)
     

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