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Designing a CNC - Rails for 2040

Discussion in 'CNC Mills/Routers' started by THRobinson, Jun 28, 2020.

  1. THRobinson

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    Hey guys... decided to build a CNC and using Sketchup to design it.

    I'm trying to use as much as possible from the premade objects from OpenBuilds, that way I know the parts are accurate and exist. What I can't find though are the rails. SBR20 I guess they're called?

    I'm looking at this guy's machine because it's the size I want and I'll be designing guitars as well. Overall I need a bed that's close to 24"x36" in order to fit guitar bodies, and long enough for bass guitar necks.

    I assumed at first he was using 2040 extrusions, but when I download rails in Sketchup they're always way taller than the rails, so, maybe using 4080? which I don't think the site has or has any premade objects for.

    Anyone know what size/name rails go with 2040?

    or, looking at the video, is he using something else?

    Also... T-slot and V-Slot... they the same thing? I googled and I don't see the difference.

    Thanks.
     
  2. Giarc

    Giarc Master
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    The SBR20s are not an OpenBuilds part.

    Openbuilds machines use V-slot which is desgned to be used with the V-wheels OpenBuilds sells. T slot does not work with wheels.

    If trying to use Openbuilds parts to make a custom design, you could base it on the LEAD CNC 1010 (40" x 40") and make it 1500 mm long so you get plenty more than your 24x36. Then it would be about 29 x 49" cutting a area. Just order everything from the parts list, but substitute two 1500mm cbeams for the y axis 1000mm cbeams. Leave out all parts that have to do with the 8mm lead screws for the Yaxis like the lead screw, antibacklash nuts, collars, couplers, et al. Then, substitute 12mm items for those parts. 12mm lead screws and antibacklash nuts are available elsewhere or what I did was buy 1/2"-10 5 start precision lead screws from McMaster-Carr. I made my own antibacklash nuts, but others here found them on ebay and they are similar to the OpenBuilds 8mm nuts where you use two per side of each axis (4 total for Y axis) to take out the backlash.
     
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  3. JustinTime

    JustinTime Journeyman
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    Basically, all these aluminum extrusions, like the 20x20, 30x30, 20x40 and so on, are T-slots. If you look at the profile you'll see the T-slots on all four sides. V-slot is the chamfered edge of the top of the T where the wheels that Craig mentioned run.
    So, while all are T-slots only those with the chamfer are V-slots.

    I have a machine that is 48" x 50". I used SBR16 which I think is plenty strong and solid. My lead screws are 16mm except on the Z axis where I use a 12mm lead screw and even that could be only 10mm.

    If you plan to build a machine like the link you've posted, out of wood, then you'll have no problem mounting the SBR but if you are going to use the aluminum profiles you'll have a challenge mounting them on the profile, which is why the V-slot are so convenient.
     
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  4. THRobinson

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    Thanks... what would I need to replace to get it to hoping 2.75"-3" height. Some guitars with carved tops are around the 2.5" thickness range... instead of the 250mm sides, grab 300mm? plus 300mm where the router attaches, and a longer lead screw, would that be all? assuming wiring is long enough...
     
  5. Giarc

    Giarc Master
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    I would think that all you would need would be the higher sides like the 300mm you suggested. Z axis should be fine at 250mm. I have a 250 mm on my custom build and I can cut 4" if I need to with the right extra long endmills. The current Z beam on the LEAD is 250mm. The plate the router mounts to is 125mm so that is the minimum amount you loose in Z travel. You will loose more if you put a homing switch on. So, you will have about 4.9 inches (125mm) of travel down without a homing switch. If you loose and inch for the switch you still have nearly 4 inches. The bigger issue is finding endmills that can cut that deep. They are available.
     
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  6. THRobinson

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    Thanks for the info... completely new to the stuff. Went to school for design, taught myself Sketchup, and now starting Fusion360 because seemed to be a lot of YouTube vids about it and it being CAD/CAM in one.

    Figured rather than get more of a headache with the electronics part, I was definitely going to grab the OpenBuilds blackbox and stepper motors to save some headache. Thought I'd design a simple base with wood parts like in that Highline Guitar video, but immediately ran into the issue of going onto 3D Warehouse and no matter what I downloaded, nothing fit or lined up.

    So... this uses the roller-skate type rollers versus the bearings on a rail... any real difference?

    One concern I have is, eventually I would like to be able to do something like this... would this machine handle that?



    Any feedback on the Fusion360 as a choice? Seen a lot of guitar people using it, but, it's fine with the Blackbox/OpenBuilds stuff?
     
  7. JustinTime

    JustinTime Journeyman
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    Yes
    Yes
     
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