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I want more power, larger work envelopes and I'm a n00b.

Discussion in 'CNC Mills/Routers' started by pharmecis, Jul 8, 2015.

  1. pharmecis

    pharmecis Well-Known
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    I'm in the process of attempting to build my first cnc machine. I have a 3D printer and I want to learn more. Since I'm in the automotive industry, the ability to make parts in house would be a boon. I'm cheap, but not CHEAP. I did a lot of reading on the available diy and turnkey machines at various price points up to $15k. The $3k and less kits and turnkey solutions left me less than awed with their capabilities and I don't want to plunk down five figures right now on something that might end up collecting dust.

    I then started doing the research as to what it would take for me to build my own machine and I came to the conclusion that I can probably spend around $2,500 and end up with a machine that has more power and a larger work envelope than what is commonly available. My end goal is a machine that can do aluminum great. If it can cut a harder metal at a much slower rate I'm elated. If it can't, oh well, wasn't counting on it but it would have been nice.

    I'm basing my build around parts sold by OB. I'll admit I bought a bunch of c beam actuators and v slot rails before I even knew what my machine would look like. I'm a hands on kind of guy, I needed to feel the product and slowly the idea began to take shape. I ended up using tinkercad to roughly model what the machine will look like. Having never done this I am making many assumptions about how things are going to work without having any data or experiences to back it up. I've been accused of worse things than shooting from the hip!

    I've gone through several revisions of the machine as I've thought about possible weak links and changed things to end up with something I hope is rather robust.

    The base of the machine is going to be a 1" plate of 6061 aluminum. The X axis will attach directly to this plate along with the support structure for the gantries. The X axis will be powered by two 1000mm c beam actuator kits. I bought them without steppers so now I need to figure out what kind of size stepper I will need to use. On top of the c beam actuators I am planning on using a 3/8" aluminum plate as the bed. The work will be attached to this plate.

    The Y axis will be constructed with twin 1000mm c beam actuators and are the gantries above. Sandwiched between the two c beams will be a 2.2kw spindle. The spindle is Chinese but the VFD is Hitachi so hopefully it works out well.

    The Z axis will be the vertical supports for the gantries. There will be four supports, two on each side. I want to only power two of the supports and am thinking that using opposing sides would be best. These will be powered by modified 500mm c beam actuators.

    I am calculating that I will have a rough effective work area of 800x800x300. I'm not shooting for a super accurate machine. At this point in my development if I'm making parts that are .01 accurate I think I'll be doing just fine. If I can hit a better accuracy, even better but .01 is the goal. As long as I can cut aluminum like butter, I'll be happy.

    I've attached an stl file w/ the design. I'd appreciate any feedback, criticism, and suggestions. I could definitely use some helping in figuring out what steppers to buy. Hopefully the 5 axis stepper driver I have is good enough at 4A. ;)

    Tinkercad link: https://tinkercad.com/things/fWHecdiL4ow
     

    Attached Files:

    #1 pharmecis, Jul 8, 2015
    Last edited: Jul 8, 2015
  2. Joe Santarsiero

    Joe Santarsiero OB addict
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    is that tinkercad link the machine you're building?
    Edit sent to inbox.
     
    #2 Joe Santarsiero, Jul 9, 2015
    Last edited: Jul 9, 2015
  3. pharmecis

    pharmecis Well-Known
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  4. Joe Santarsiero

    Joe Santarsiero OB addict
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    How many motors are you going to have on the z?
     
  5. Ryan James

    Ryan James Well-Known
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    I have to say that I was looking at a design close to this. I was using two motors for the z-axis instead of four, more like a 3d printer. I wasn't sure it would be a viable option, though. Interested to see how yours turns out.
     
  6. pharmecis

    pharmecis Well-Known
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    There will be two stepper motors per axis. The current sketch in tinkercad has the actuator beams color coded and you can even see the small black stepper motors that are attached to them. The X is blue, the Y is red and the Z is green. In the diagram I have the motors placed on opposing ends. I'm not sure if same end or opposite end placement is better but I guessed on opposite ends especially for the Z since I have to raise and lower the bridge.

    The controller kit I bought is a 6 axis controller with a 5 axis stepper driver board. I wasn't planning on 6 stepper motors to begin with. I was going to link axis a and b with x and y in the software but now I might have to run at least one axis with the motors in parallel, whichever axis is going to take less force to move I guess as there is only 4A output available on that driver board.
     
  7. Joe Santarsiero

    Joe Santarsiero OB addict
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    cool. What board is it?
     
  8. pharmecis

    pharmecis Well-Known
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  9. JustinTime

    JustinTime Master
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    If the Y axis is red than I think you can use only one stepper on that axis.
     
  10. pharmecis

    pharmecis Well-Known
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    Why is that if you don't mind me asking?
     
  11. JustinTime

    JustinTime Master
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    The force, or weight, on the red part is very little, compared to the other axis' and therefor the lever force is almost nil. The router, or what ever you are going to install, slides on the two outer rails. I think that it will run smooth and that one stepper will do the job perfectly. I don't even think that it has to be a very big stepper but that depends on the weight of the router.
     
  12. Joe Santarsiero

    Joe Santarsiero OB addict
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    2.2kw!
     
  13. pharmecis

    pharmecis Well-Known
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    Yeah it's about 18 lbs as I went with a much more powerful spindle than what is normally used in these builds!

    I will test, if I only need one stepper that will be great!
     
  14. JustinTime

    JustinTime Master
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    I see, Joe. I think a ~400 oz/in stepper will have no problem with it

    Edit: phamecis was posting as I was writing. 18lbs is heavy. So maybe a bigger stepper will be needed but I still think that one is enough.
     
  15. pharmecis

    pharmecis Well-Known
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    Holy crap. Just got the cast aluminum mount for the spindle. It's got to be 6 or 7 lbs itself!

    Once I get this thing up and running, one of the first things I will be doing is making new brackets for the spindle!
     
    #15 pharmecis, Jul 14, 2015
    Last edited: Jul 14, 2015
  16. pharmecis

    pharmecis Well-Known
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    Got the spindle in and I'm breathing a small sigh of relief. Spindle and bracket together weigh 15 pounds.
     
    Joe Santarsiero likes this.
  17. Florian Bauereisen

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    Hi,
    i simply doubt that this setup will work.
    your z supports are braced forward and aft but non to the sides. Just compare to a cardhouse to get what i am after.
    The red x (?)-
    just like that? no strenghening at all? Two extrusions hanging in there totally free?All the weitght hanging between? Putting 15 pounds of spindle onto this will make it bend whatever you may belive or hope.
    Btw what is stopping the spindle from twisting the whole red x- axis while cutting?
    There is simply no static at all within this red setup.
    Compare with modern Bridge-building than you might understand.

    Or have a look here - guess that guy spend quite the double of what you are willing to and still only has a relatively small machine.(and thus more easy to handle- designwise/static)
    fräse.jpg
    Still his y-supports (sideplates) seem awfully slim and the wagons beeing pretty close together (get them spaced appart as far as possible - without loosing too much on y)


    Going bigger is fare more easy with a standard gantry setup, worst to worry is the x-axis, everything else stays more or less the same.
    Higher z is the most complex and expensive to expand on a cnc.
    Don´t belive me - just compare professional machines offered with different z hights.

    The bed (y) is ok as it is , supports spaced appart for stability - but if you really fancy a bigger machine it is more easy to achive with a moving gantry instead of a moving bed.

    Sorry if i may seem blunt or rude - that is not my intention. Just think, compare and read about cnc around the net and you will see i just trying to prefent frustration.
    A setup like yours might be possilbe with the opposite- a tiny machine using lightweight spindles.

    greets

    flo
     

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