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In-Decisions - Suggestions requested / Check my logic

Discussion in 'CNC Mills/Routers' started by robertfontaine, Oct 3, 2017.

  1. robertfontaine

    robertfontaine Well-Known
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    OK...
    I have begun to put money aside...

    I know I want a CNC and I know I want
    - to do small pieces. < 15x15x1"
    - aluminum
    - repeatability and accuracy don't have to be machine shop quality - smooth clean cuts and carpentry accuracy is adequate to start
    - one off prototypes to start, i.e. Doesn't have to be fast.

    I also know that I want to do this in baby steps. I may want a 900w - 1.5kw spindle (both for speed and noise) and roller bearings (for more precision) but that is not where I am going to start.

    I am thinking that I am starting with a Dewalt or Makita set up initially with the idea that if my parts can pay for themselves I will start to upgrade with whatever money might come from making things.

    The path of CBeam XL to CBeam Sphinx is kind of appealing to me as it seems to provide a means to start making small aluminum parts, as well as plates for the Sphinx itself.

    I have been looking at the CBeam XL, The Shapeoko 3, The MillRight Carve King and the X-Carve. Heck I would be looking at the MillRight M3 if the working area was a little bigger.

    From an platform perspective I think MillRight is out despite it's appealing price.
    Price wise -
    Shapeoko 3 is 1,099 w/out router
    C-Beam XL w/out router - 1,593.04
    Mechanical Bundle w/ motors 1323.40
    Smoothie Board $207.26
    PSU 62.38
    X-Carve w/out router 1086.98

    So I assume all 3 can cut aluminum with the Dewalt router
    When I look at the 3 the openbuilds appears to be the beefiest and the shapeoko the simplest.
    The X-Carve seems to significantly less rigidly built than the other two...
    - I suspect it works fine but I wonder if it has the ability to scale up to a slower higher wattage spindle?

    Givin the Shapeoko 3 and the X-Carve are essentially the same price I am left looking at the

    CBeam XL and Shapeoko 3. So the question is whether the CBeam XL is worth the 50% higher price?
    Shapeokos have been been modded up with 1.5kw spindles (with appropriate feeds and speed) CBeams have been upgraded to the even heftier Sphinx.

    But none of them are commercial machines so with all of them some compromise is necessary to running them.

    It seems like the Shapeoko 3 is a better value for my use cases than the CBeam XL

    Am I missing anything?

    -- Thanks,
    R



    [​IMG] [​IMG] [​IMG]
     
  2. robertfontaine

    robertfontaine Well-Known
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    another option I found ...

    GarageworxCNC done in steel

    [​IMG]
     
  3. Kevon Ritter

    Kevon Ritter Veteran
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    Linear motion:
    I don't have any experience with belts, nor do I plan to ever have any. Lead/ball screws are far more stable. That eliminates the Shapeoko 3, the X-Carve, and the unmentioned Ox.

    Rigidity:
    The greater the machining area, the more the overall machine will flex. Every time a length is doubled, the stiffness has to be quadrupled to equate to the same stiffness. With that said, if you want to effectively cut rigid materials such as aluminum, you should be looking into a physically smaller machine.

    Out of all the machines you listed, the C-Beam would be the best, but even that I don't like all that much do to the bed design. The bed on a fixed table has the capability of being far more rigid. With that said, I built a 500mm based Sphinx (330mm x 330mm). I mainly cut aluminum, carbon fiber, and acrylic. I don't make 0.2mm passes, which seems to be common around here. I make much larger 2mm passes, and that's still conservative. Of course, there are many factors to account for, but that's just a rough idea.

    Figure out what you want to do, not what you kind of want, and build towards that.
     
    GrayUK likes this.
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Builder

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    The key differences are power and resolution.
    • The Shapeoko 3 is belt driven and uses 2.0A 125 oz.in. motors. Assuming the belt is a GT2, the machine moves the carriage 0.2mm per step.
    • The C-Beam XL is screw driven and uses 3.0A 345 oz.in motors. The TR8x8 screws of the C-Beam XL move the carriage 0.04mm per step.
    Starting with resolution, native resolution of the C-Beam XL is five times that of the Shapeoko 3. Not a big issue when working with wood but a lot more important when milling aluminum.
    And as for power, screws have far more mechanical advantage than belts. And when the mechanical advantage is combined with the far more substantial motors, these machines are in two entirely different leagues. And again, power is not a big issue when working with wood but a lot more important when milling aluminum.

    So as to whether it's worth 50% more, the answer is fairly obvious as the C-Beam is a much more substantial machine. But I'm questioning if the difference you show is actually 50% as the Shapeoko 3 price you show appears to be in US$ and the C-Beam XL price you are showing in CA$. You are also including a far more substantial controller with the C-Beam XL which also heavily biases the price difference. When you put apples to apples, the Sparkfun version of the Shapeoko 3 is $1346.09 CAD and the C-Beam XL with a similar level of controller would be about $1360 CAD (plus shipping). You could even drop another $80 CAD off that total by dropping down to the 176 oz.in. nema 32s which should be more than sufficient. With all this being said however, apples to apples approach has its limitations. Most controllers are only capable of 2.0 Amps so you can't get full value out of 3.0 Amp motors. In order to do that you'll need to add the stepper drivers which will add another $200 CAD to the price. But even then, adding in the better controller and the stepper drivers which will make it a far more impressive and smoother operating machine, you're still only at $1730 CAD (plus shipping) which is only a 29% difference (before shipping is factored in).

    I do see a lot of positives in the Shapeoko 3. First off, it'll do the job you require. It offers the specific work area you need and it will cut aluminum. The nature of the extrusions and the way they are connected makes also makes it a fairly rigid system. It's limitations however come in power, resolution, and expandability. The C-beam XL doesn't quite offer the area you need and costs more but will do the job more efficiently. It is also easily expandable/re-configurable to where it can grow with your needs. This is really something you're going to have to do the soul searching on though. I can tell you what I'd go with but I would hardly be considered impartial on the matter. ;)

    (I'd go Sphinx style but with stock OpenBuilds plates in a 750x750 format which would give you all you seek at a slightly lower cost than the C-Beam XL. Sketch attached below)
     

    Attached Files:

  5. robertfontaine

    robertfontaine Well-Known
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    Thank you Rick. Just what I was looking for.
     
  6. DA_Spec

    DA_Spec Well-Known
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    Robert Fontaine that sounds like a french canadian name ?
     
  7. robertfontaine

    robertfontaine Well-Known
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    Oui.... but my french is non-existent.

    Now that I know that I can buy Openbuilds packages from Canada without the evils of UPS Brokerage decision making has become quite a bit easier. It will take me about 4 months to put aside adequate cash for a CNC mill but in the meantime I have started to learn and create some simple designs in Fusion 360 for my little stenogaphy keyboards and am outsourcing my first batch of prototypes (so painfully slow). I need to work on the design V2 of my PCB as well as the mechanical parts so between assembling V1 and designing V2 my weekends should be busy till I have enough cash in the Paypal account It will be wonderful to fail faster.
     

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