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5 axis machine

Discussion in 'Concepts and Ideas' started by Mark Carew, Jun 25, 2015.

  1. Mark Carew

    Mark Carew OpenBuilds Team
    Staff Member Resident Builder Builder

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    Hey guys, up for a challenge build? check this one out
    This machine is very small and so does very small parts but, I think we could scale a machine similar to this bad boy up to a machine to make useful larger parts and this would make a great Open Source Build!
    I think the most exciting part about an Open Source Build like this would be having 5 axis Open Source software for future Builds.
    What do you guys think?

    https://www.kickstarter.com/project...t-5-axis-cnc-mill-for-your-deskt?ref=category

    Capture.JPG
     
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  2. orangezero

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    I was a tiny bit disappointed seeing that they were using autodesk fusion 360. I was really hoping they would build their own software...

    Is there even inexpensive, good 4D axis software? 5D would seem to get into highly professional stuff that is $20,000+ or requires yearly subscriptions well over $1000 a year. I haven't tried the free version of fusion 360, but I thought they were taking out their cam eventually and moving it into the subscription area.

    A bigger machine would be cool, but I wonder how drastically the resolution changes as you go from the center of the piece off to the far edges. For this one, it would only be 2-3 inches you'd have to worry about. I can't imagine how hard it would be to deal with a 12in or 24in plate.

    But yeah, I messed around designing something similar to this when I found their website. At the time I was looking to build a tiny machine with a workspace of only 4x4x6, but needed it small and stable. I like their ideas.
     
  3. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

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    I have plans to add 4th axis to SketchUcam... so you would be able to specify an angle (for A or B axis) for a set of Gcode. then you can use the multiple drawings method to generate Gcode for each side of an object, then join the files for a complete machine cycle.

    keep in mind that 4th and 5th axis does not have to be all in software, you can use them right now in whatever CAM you have, generate code for a flat object, then open the gcode in an editor like notepad++ and add a line like
    G00 A15
    before the actual cutting starts and the A axis will turn to 15 degrees.

    simple
     
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  4. Rob Taylor

    Rob Taylor Veteran
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    I like these compact five-axis machines. They seem much more feasible than the large enclosed turret-type 5-axis industrial machines.

    I'd assume that the CAD/CAM primarily deals with rotation (when say, "spinning" a cross-sectional Bezier curve) in degrees rather than tangential distance, so theoretically it should be the same (you just have to make sure your rotary axes can go down to pretty low fractions of a degree?).

    Anyone? It does seem to be relevant, if not.
     
  5. orangezero

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    Good to know. I haven't thought too much about trying to do it that way. I'll have to add "sketchUcam" to my todo list.
     
  6. orangezero

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    I guess I was thinking of it like this. Say you tell the machine to rotate 10 degrees, but it only rotates 9.9 degrees. That would seem to be insignificant at 3-4 inches, but at 24 or 36 inches that might be a bigger error. I should figure out the equations rather than guessing online. And honestly, if this is true, maybe that still isn't a big deal for the vast majority of us doing it as a hobby.

    Then again, perhaps this is all cancelled out by making other adjustments, such as increasing the gear ratio on the rotating "disc."

    In any case, I do not want to discourage anyone from attempting this... :) (and don't forget photos and photos!!!)

    I'd also highly encourage anyone to add those changes to sketchUcam to automate 4D and 5D a bit, and then promote that fact. That would be a nice addition to not have to manually edit g-code (which would probably scare off some people). I've read many, many threads with people lamenting the lack of decent 4D cam software of any kind at a reasonable price.
     
  7. Rob Taylor

    Rob Taylor Veteran
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    Ohhh, gotcha. I guess if that's a backlash issue, you need to add rotary encoder feedback or change the design of the rotary drive (chain instead of spur gears, for example). If it's the software/hardware interface itself, well, that's a problem. :p

    Otherwise, I guess it's just the same cost of doing business as every other actuation in hobbyist motion control. I think it'd be important to ensure a rotary drive went down to at least 1/100th of a degree though, or any linear movements relying on meeting the ends of the arc may end up with serious problems.

    Axis-wise, I do have my own CAM-exporter-controller pipeline software thingy planned, but it's very much a back burner project, I don't expect to get anywhere with it for at least five years, possibly in conjunction with a secondary motion control project for non-machining purposes. However, I do want it to be 5-axis plug-and-play once complete.
     
  8. David the swarfer

    David the swarfer OpenBuilds Team
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    That is exactly what you have to do, have a a very high angular resolution to match the size of your workpieces.
    Say you have a 200 step per rev motor, with a 16x micro stepping driver.
    ergo, 3200 steps per rev.

    now you want to drive a workpiece of say 6" diameter and have 0.001" resolution.
    pi * D = pi * 6 = circumference of 18.85"
    circ / desired res = 18.85 / 0.0001 = 18850 steps per rev

    18850 / motors steps per rev = 18850 / 3200 = 5.89
    so you need a gear ratio of at least 5.89:1 to get the resolution you want.

    now try it with a 20" workpiece (-:
    (gear ratio is 29.64:1 or so, but don't forget that 0.001" is still pretty large, what about 0.01mm?)

    all this reduction will impact speed, and larger workpieces with higher resolution need ever higher gear reductions, which is why harmonic drives are often used.

    code already added to development branch which will become SketchUcam v1.3b (-:
    those who already have a 4th axis and want to be beta testers, send me a personal message. It will now output commands for A, B and C axes, so in fact 6D.

    I believe the most common hobby implementation will be a B axis, a rotary axis in line with the Y axis. Using this one might easily machine 4 sides of an object (in my case I am aiming at rc model fuselages, but the idea applies to anything).

    here is an example of 4 sided working...
     

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