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Attaching 'rack' to v-slot

Discussion in 'CNC Mills/Routers' started by Sage, Dec 19, 2013.

  1. bobt

    bobt Well-Known
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    Here is a forum discussion about using rack and pinon with MakerSlide extrusions.

    http://www.buildlog.net/forum/viewtopic.php?f=16&t=1296&p=14023&hilit=rack#p14023

    Here is where the discussion starts and is 88 entries long. It talks about the problems and changes
    that were needed to make it work.

    http://www.buildlog.net/forum/viewtopic.php?f=16&t=1296

    It is basically similar to what vslot is and was used successfully to make a CNC Plasma Cutter.
    Let's not reinvent the wheel here when others have made the trip before us.
    Here is a video of his Plasma cutter that uses Rack and Pinon with MakerSlide.



    Now I don't understand why this cannot be done using V-Slot instead.

    Bob
     
    #31 bobt, Sep 8, 2014
    Last edited: Sep 8, 2014
  2. Jonny Norris

    Jonny Norris Well-Known
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    I personally wouldn't like to rely on the slots alone, you may be able to just set motor position and it will be fine. But there's not many easy solutions if it starts slipping. The eccentrics already on the gantry are putting force in a single direction, so they will be a slight force applied to the rack but restricted by profile. The rack and pinion will need to be in complete harmony with each other with 0 room for deflection. Any and you will get either loss of mesh or a wobly gantry.

    You could put eccentrics on the motor but turning 4 at the same time will be interesting. Sprung loaded rack.. Okay sounds interesting but I dont think they actually need forcing together here just floating with the correct mesh.

    Maybe a servo might be your best option instead of direct drive.

    I'm still going to try the floating rack at the cost of two holes on each gantry for v wheels and a couple of brackets at each end. If it doesn't work. No real loss.
     
  3. Hytech2k

    Hytech2k Veteran
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    I have run a rack and pinion system on my homebuilt 5' x 9' machine for over a year now and couldn't be happier with it. I thought I might be able to give insight on how mine works. I am using JoesCNC Evolution 3/4 alum plates for my x and y and I have cncrouterparts Nema 34 Pro drives on each. The Pro drives IMHO are great, they pivot on a needle bearings and have a nice tension system to keep the drive engaged in the track to prevent slipping, minimize any backlash, and ride any irregularities in the rack. My drives are belt reduced 3.2-1 and the nema 23's are 2-1. I am thinking of changing the side plates on the Y on my next ox to try and incorporate R&P and the nema 23 drives. I run my machine probably 10 hrs a day 5 days a week, made over 700 products on it so far. I did ALOT of reseach before building my first machine, alot of people having trouble with long lead screws, others issues about tightening chains, and hit and miss on belt systems (largely dependent on the size and type of belts used). It might cost alittle more up front but for reliability, durability, and ease on maintenance R&P is the way to go in my opinion.

    IMG_7597.JPG IMG_7598.JPG IMG_7599.JPG IMG_7600.JPG IMG_7601.JPG
     
    pmany and Balu like this.
  4. GrayUK

    GrayUK Openbuilds Team Elder
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    That's a pretty impresive set up there. :thumbsup:
    Would appreciate some more pictures if you have any. :)

    Gray
     
  5. Balu

    Balu Well-Known
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    I'd like to second that request :). For now I don't understand half of what you wrote since I'm very new with all these parts, but I know I'd want all of that ;).

    A lot of people here would probably be really interested on the basic frame too because of the lengths of your axes.
     
  6. Hytech2k

    Hytech2k Veteran
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    I'll get it cleaned up and take a few photos of it tomorrow, it's design is pretty simple and straight forward.

    Thanks

    Gerald
     
  7. Hytech2k

    Hytech2k Veteran
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    Pix as promised. I don't want to hijack someone elses thread so i'll keep it brief. Just wanting to show a different way to use rack and pinon. The base is just standard dimension lumber build with 2x4's and 2x6's heavily braced. I used heavy gauge 8020 components for the Y and Gantry. Check my profile for specs on the electronics. I don't see why this type of R&P couldn't be scaled down to work with the smaller machines. CNCrouterparts has the drives in nema 23, or in true maker fashion design the drive from scratch, just have to find suitable rack and redesign the x and y plates to utilize them ..
     

    Attached Files:

    #37 Hytech2k, Nov 4, 2014
    Last edited: Nov 4, 2014
    GrayUK and Balu like this.
  8. Steve123

    Steve123 New
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    rail_closeup.jpg Here is another CNC Router, the Gryphon, using rack and pinion just like the CNC Mogul. It may just be a copy of the Mogul or rebranding of the Mogul. If you look closely you can see the rail in the slot.

    http://www.gryphoncnc.com/
     
  9. Eric Foster

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  10. Jonny Norris

    Jonny Norris Well-Known
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    Quick question, I almost took the plunge and bought a load of rack and pinion, when it occurred to me how much easier it would be to use lead screws instead. Just need to move the motors onto some extra plates and bolt on sum nuts. What advantages are there to rack over lead screw?
     
  11. jevaise

    jevaise New
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  12. CutAboveZ

    CutAboveZ New
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