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Thread: YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE

  1. #13
    Registered JoanTheSpark's Avatar
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    Default Re: YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE

    To start with you do not have a 'gantry'.
    A gantry is a beam that is supported on both ends, for stiffness with a traveler along that beam.

    As for cutting forces and related discussions:
    https://www.cnczone.com/forums/mechanical-calculations-engineering-design/100340-cutting-force-milling.html
    (the pdfs linked are available via https://web.archive.org/)
    https://www.mmsonline.com/articles/a...s-and-formulas
    https://www.cnczone.com/forums/gener...s-milling.html
    Be aware that this all is static and doesn't take into account dynamic forces that are results of oscillations and your YAAS will produce a lot of those, due to it's design.

    As for being a negative nancy.. well, you seem to use a very nice CAD package there, what is it?
    Does it have FEM?
    How about you put a 50N (~5kg) force at the tip of that spindle, pulling in the direction of the x axis and look what deflections you get?
    The anchor/non moving part would be the table your part is mounted on for that analysis.
    If your CAD tool doesn't have that but can export a STEP model I'd happily do that for you in my tool.

    Attached Thumbnails Attached Thumbnails YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE-_badexample-jpg  


  2. #14
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    Default Re: YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE

    Quote Originally Posted by aortiz21 View Post
    I believe I made it clear that I am increasing the stiffness of the frame and gantru which is why I asked the two questions above.

    However, it looks like most people would rather criticize than provide helpful answers. Not sure who they're trying to impress.
    Critique is helpful. We're not telling you to give up and go away, we're saying that there are clear design considerations that you're either ignoring deliberately or are unaware of - saying "I am increasing the stiffness of the frame and gantry" without specifying how just leaves the whole thng open to misinterpretation - if you want valid design input, you need to offer more information than you have thus far.

    For starters, you don't have a gantry - that's an overarching frame that's supported at both ends. You've got a cantilevered spindle instead, which is a much weaker system of attachment when it comes to dealing with the kind of dynamic loading that a mill or router has to deal with. Ordinarily, this is resolved by having as short a cantilever as is possible, which is why the spindle is never normally mounted away from the z axis like that.

    Frame stiffness is also only part of the issue - how are you looking at vibration damping? Again, adding weigt is a great way of eliminating it as a problem, but the kind of airspace design you have at the moment has very few avenues available to it to be able to resolve that.

    When I said to stop spending money right now, I didn't say to quit, I said to continue researching the project - I'd really like to see you succeed, but I genuinely do not believe that you're going to get very far ith this current design, because it's just not going to be stiff enough to have any degree of consistency or repeatability in the cuts that it makes. This is too close to a 3d printer design, and the requirements are very, very different. 3D printers don't have any kind of serious load attached to the printing head - they're depositing material in what's effectiely a zero-resistance environment (unless something's gone very wrong), whereas a mill or router has got a continuous dynamic load applied to it, because it's being forced against material that it's expected to cut away.

    The pdf article you cited pertains specifically to toolbit deflection, and assumes a certain degree of rigidity in the CNC machine frame that yours won't have, due to having that massive arm hanging off of it. If the spindle were brought right back in to the Z axis, then it might be more relevant. As for the thread link, 20klbs probably isn't a bad figure to aim for, but you really do need to run an FEA test on your current design based on that. I absolutely guarantee that the spindle arm will need a thorough redesign.



  3. #15
    Community Moderator ger21's Avatar
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    Default Re: YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE

    However, it looks like most people would rather criticize than provide helpful answers
    No, they are trying to be helpful. You just aren't listening.

    Gerry

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  4. #16
    *Registered User* aortiz21's Avatar
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    Default Re: YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE

    Quote Originally Posted by JoanTheSpark View Post
    To start with you do not have a 'gantry'.
    A gantry is a beam that is supported on both ends, for stiffness with a traveler along that beam.

    As for cutting forces and related discussions:
    https://www.cnczone.com/forums/mechanical-calculations-engineering-design/100340-cutting-force-milling.html
    (the pdfs linked are available via https://web.archive.org/)
    https://www.mmsonline.com/articles/a...s-and-formulas
    https://www.cnczone.com/forums/gener...s-milling.html
    Be aware that this all is static and doesn't take into account dynamic forces that are results of oscillations and your YAAS will produce a lot of those, due to it's design.

    As for being a negative nancy.. well, you seem to use a very nice CAD package there, what is it?
    Does it have FEM?
    How about you put a 50N (~5kg) force at the tip of that spindle, pulling in the direction of the x axis and look what deflections you get?
    The anchor/non moving part would be the table your part is mounted on for that analysis.
    If your CAD tool doesn't have that but can export a STEP model I'd happily do that for you in my tool.
    Thanks for the links! I'll go through them tonight. I'm using Solidworks rendered with KeyShot. It does have FEM, so I'll do some analysis with the setup you described.

    Critique is helpful. We're not telling you to give up and go away, we're saying that there are clear design considerations that you're either ignoring deliberately or are unaware of - saying "I am increasing the stiffness of the frame and gantry" without specifying how just leaves the whole thng open to misinterpretation - if you want valid design input, you need to offer more information than you have thus far.

    For starters, you don't have a gantry - that's an overarching frame that's supported at both ends. You've got a cantilevered spindle instead, which is a much weaker system of attachment when it comes to dealing with the kind of dynamic loading that a mill or router has to deal with. Ordinarily, this is resolved by having as short a cantilever as is possible, which is why the spindle is never normally mounted away from the z axis like that.

    Frame stiffness is also only part of the issue - how are you looking at vibration damping? Again, adding weigt is a great way of eliminating it as a problem, but the kind of airspace design you have at the moment has very few avenues available to it to be able to resolve that.

    When I said to stop spending money right now, I didn't say to quit, I said to continue researching the project - I'd really like to see you succeed, but I genuinely do not believe that you're going to get very far ith this current design, because it's just not going to be stiff enough to have any degree of consistency or repeatability in the cuts that it makes. This is too close to a 3d printer design, and the requirements are very, very different. 3D printers don't have any kind of serious load attached to the printing head - they're depositing material in what's effectiely a zero-resistance environment (unless something's gone very wrong), whereas a mill or router has got a continuous dynamic load applied to it, because it's being forced against material that it's expected to cut away.

    The pdf article you cited pertains specifically to toolbit deflection, and assumes a certain degree of rigidity in the CNC machine frame that yours won't have, due to having that massive arm hanging off of it. If the spindle were brought right back in to the Z axis, then it might be more relevant. As for the thread link, 20klbs probably isn't a bad figure to aim for, but you really do need to run an FEA test on your current design based on that. I absolutely guarantee that the spindle arm will need a thorough redesign.
    I appreciate the input! I'm going to modify the spindle arm based on FEA to remove the cantilever arm. I'm also going to brace the frame with more rectangular tubing or trusses. For vibration - I'm exploring drilling holes in the tubing and filling with concrete post welding to add mass. It seems some members here had some luck with non expanding grout or epoxy granite.



  5. #17
    Registered GerryG's Avatar
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    Default Re: YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE

    Quote Originally Posted by aortiz21 View Post
    I appreciate the input! I'm going to modify the spindle arm based on FEA to remove the cantilever arm. I'm also going to brace the frame with more rectangular tubing or trusses. For vibration - I'm exploring drilling holes in the tubing and filling with concrete post welding to add mass. It seems some members here had some luck with non expanding grout or epoxy granite.
    Increased cross-bracing and mass will definitely help. Epoxy granite is a pretty popular awy of going about adding mass to a hollow structure, so that's a good call.

    Peronally, my next step would be to make everything more compact, to be honest - you've got a lot of travel into empty space in the current design that won't necessarily be of much benefit. It might be worth looking a bit more closely into what exactly you're intending to make with this: is it going to be processing sheets or blocks of material? If it's sheets or flatter material, then a gantry-style system with a lot of travel in X or Y would be easiest, with the A/B rotations happening on the head instead of the workpiece. If it's a block that you're looking at working on, then you can cut the amount of X/Y travel right down, and eliminate all the distance that'llbe amplifying vibrations and instability. That's when a trunnion and turntable will make the most sense.

    There's a certain amount of crossover that can happen between these design ideas, but there really does need to be a bias that you've chosen, because it's far easier to design for one thing that can accomodate another, than to design specifically for both, if that makes any sense.

    IIRC, you've already gone and bought some long lengths of steel, right? If that's the case, then I'd really be looking to go down the router table route, with the A/B articulations on the head. As many people have proven it's more than possible to machine metals on a router, provided it's stiff and heavy enough.



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YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE

YAAS! DIY 5 AXIS VERTICAL MILL - OPEN SOURCE