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C-beam or V-Rail for metal milling build?

Discussion in 'CNC Mills/Routers' started by MarkM_NJ, May 7, 2017.

  1. MarkM_NJ

    MarkM_NJ New
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    Hi everyone!
    I'm planning on building a cnc machine with the primary focus on milling aluminum, will do some mdf, plywood and -Lexi as well. I'm going to be using 1000mm lead screws for x and y. I was thinking about building the ox metal cnc but then started seeing the c-beam designs. Would I be better off going with with a c-beam design? And for the gantry plates is it better to go with the ox plates on c-beam or is it better to have the mini wheels ride inside the track like the sphinx? I take it it's more rigid to have dual anti-backlash nuts? Any input would be great!

    Thanks,
    Mark
     
  2. OpenBuildsAccount1

    OpenBuildsAccount1 Well-Known
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    Hey!

    I had the same intention when I purchased my C-BEAM.

    Let me tell you my experience.

    I purchased the C-BEAM kit over two years ago from the store stock, a Tiny-G a dewalt 611 Router, some carbide bits and a think & tinker 1/8" collet set, all in all it ran me about ~1200 bucks for all that jazz.

    It took a me a few weekends to put the C-BEAM together, but I got it together. I never ended up running anything for about a year as life got in the way, but when I started running things, I noticed a few things about it.

    1.) Configuring the Tiny-G is a HEADACHE.
    2.) This thing is LOUD-LOUD-LOUD (make an enclosure)
    3.) The single rod and the anti-backlash nut in the acme leadscrew are... not that great
    4.) Debri becomes a problem!

    When assembling the lead-screw to the assembly it seemed to have a bit of flex, but I followed the assembly videos to a T. I also had a bit of trouble getting the machine square. I can't seem to cut perfect circles, still trying to figure that one out.

    The lead-screw faces up in the aluminum extrusion column, which let's flying debri into the chamber with the potential to damage your leadscrew.

    What do I recommend?
    1.) Get a Carvey or Nomad883 if you want out of the box cutting, if you want a project that's more assembly, more tinkering and less cutting, then build your own, but this will give you weeks to months of "fun" putting the project together and trying to calibrate. Substitute that with an x-carve or shapeoko for a project-kit CNC that has good "out-of-the-box" features.

    Otherwise, I would go with a sphinx style design so it keeps your Y motion free of debri and gives you more freedom.

    Factor in the cost of building housing. Seriously unless you have a shop and wear earplugs all day, you're not going to want to run this thing ever, unless you have a shell on it.

    I actually came here looking for upgrade suggestions, because I'm ready to sell my c-beam and buy a carvey because I'm tired of the headache and project cost I would need to dump into this thing to make it better, but I might look around and see if I can't get some mods to address the issues I just told you about (still, going to take a while to get them installed)

    Hope this helps!
     
    Dray oz likes this.
  3. Kevon Ritter

    Kevon Ritter Veteran
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    I would consider the Carvey to be a major downgrade. Same for the Nomad.
    - unsupported rails
    - gutless spindle
    - work area of a printer
    - that price tag!

    I can't really comment on the X-Carve other than the facts that it has a tiny gantry extrusion and uses belts.
    If you can build a cnc machine, how hard is it to build an enclosure? They are all going to be messy so don't buy into to the pretty newly assembled pictures.

    I personally built a Sphinx. I don't like moving tables as it only adds room for flex. Mini vs regular v-wheels don't matter nearly as much as placement. Look at how spread out they are on some designs, while other designs are super tight. The former will handle loads better, but at the same time requires more space per axis which directly results in less travel. In the end, you figure out what you want to do, then find the design that works best.
     
    Rick 2.0 likes this.
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
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    If you're going with screws you might as well go with the C-Beam framing as it is the easiest to integrate screws into. And there is no need for special plates. One good example would be the C-Beam Prefab Untitled. Several of the forum members have converted their C-Beam XL builds into a fixed bed 1000 x 1000 layout and have created similar layouts.

    As for outside or inset wheels, it's kind of a hard call as there are justifications for both directions. With the outside wheels as in the example above, the wheels provide a good rigid connection to the track but as the rails have to span end to end there is the potential for flex in the rails. With the inset wheels there is more potential for flex at the side plates but the rails can easily be braced to prevent lateral and torsional flexure. I am more of a proponent of the inset wheels approach as I feel the side plate flexure is easily resolved in the stiffness of the side plates and the rigidity of the connections to the X-axis beam above. (An example of what I'm referring to can be found here.) But again as there is no hard and fast data it all comes down to personal preference (or gut feeling as is more often the case).

    Toward the issue of milling aluminum the most important aspect is making the framework and the machine as rigid as possible. Looseness in any manner allows the bit to skim off the cutting edge rather than biting into it. And the greatest key to making a system as rigid as possible is keeping it as small as you feel you can possibly work with. Don't just go with 1000 because it's there. If 800 is the magic number for your needs, cut it down to 800. That 20 percent less can cut your system flexure by upwards of 50 percent. Every little bit counts.

    BTW, if noise levels are a potential problem consider the little Makita trim router. Can't personally verify but other forum members have left favorable comments on the lesser noise levels.
     
  5. MarkM_NJ

    MarkM_NJ New
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    Thanks for the replies!
    I currently have a mpcnc that I built. It's 40"x40"x3.5"z. I'm able to mill aluminum on it but very slowly, so I'm able to make any plates that I would need. I have a 500w spindle on it and love how quite it is. I may go with another spindle on the new build but a little stronger then the 500w, but I'll also check out the Makita. I definitely want to get away from belts for the new machine. I'm working with 24"x48" 6061 T6 aluminum, have been cutting it in half. So I need to at the minimum be able to mill 24"x24" plates with enough room for clamping. I'll see how much I can scale down the build, thinking about going with the shpinx design. Thanks for the suggestions, gives me some homework to do.
     

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