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  1. #11
    Quote Originally Posted by Chaz View Post
    Just to confirm you are referring to swapping the rail and cart here on the Z Axis?
    I was actually referring to the X. At the bottom you have two linear rails bolted to an enormous structure, most of which is superfluous, you only really need the bit under the gantry.
    If you fit the linear blocks to the bit under the gantry and the rails to the table then the support will always be under the tool.
    You lose an unnecessary overhang.

  2. #12
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 14 Hours Ago Has been a member for 4-5 years. Has a total post count of 973. Received thanks 69 times, giving thanks to others 42 times.
    Quote Originally Posted by Robin Hewitt View Post
    I was actually referring to the X. At the bottom you have two linear rails bolted to an enormous structure, most of which is superfluous, you only really need the bit under the gantry.
    If you fit the linear blocks to the bit under the gantry and the rails to the table then the support will always be under the tool.
    You lose an unnecessary overhang.
    Ah, ok, understood.

    I'm just trying to find the reference design / document that I used. I did note that this is not final but the shape (with more support) is basically a triangle.

    I am however more than happy to make changes based on experience, one of the reasons why I have started this thread.

  3. #13
    The way i see it, if you go with high speed spindle, fixed gantry would be better, if you go with servo motor and Bt30, the VMC shape will be better. So at the end there is not so much to consider which shape you go.

    With that size bearings and rails length, overhang will be irrelevant. You could try to make it small, just for a designers satisfaction though, but its not necessary.
    project 1 , 2, Dust Shoe ...

  4. #14
    I cannot claim any "experience" making super routers, but I have made a few tables and converted a couple of milling machines. But enough of the X, here are my thoughts on the Z.
    With a knee mill you have 2 controls for the Z, you can lift the table of lower the quill. A round column mill is similarly adjustable. When you CNC it you probably motorise the quill and use the other, heavy duty adjustment, to optimise the quill travel and get maximum support on a job by job basis. You would be lost without this double control of the Z and yet nobody puts it in a home build.
    I suggest you make the entire gantry moveable in the Z with some big bolts so you can lock it in the optimum position. I do have expertise in this because when the locking bolts went on my mill everything went to hell in a hand basket PDQ

  5. #15
    That's quite a neat idea there Robin, have never seen that applied yet.

    I guess it depends on the intended use of the monster mill, spindle power and speed could dictate smaller (<10mm) cutters which would then indicate that smaller workpieces would be used - no use tickling a 300kg lump with a 3mm end mill I think.

    That being said, a dual position gantry maybe offering the tool a 0 - 150mm and 150 - 300mm range could be useful, would need an assisted method of raising/lowering the gantry though - two trapezoidal leadscrews might work along with some heavy clamping method when in position.

  6. #16
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 14 Hours Ago Has been a member for 4-5 years. Has a total post count of 973. Received thanks 69 times, giving thanks to others 42 times.
    Quote Originally Posted by Robin Hewitt View Post
    I was actually referring to the X. At the bottom you have two linear rails bolted to an enormous structure, most of which is superfluous, you only really need the bit under the gantry.
    If you fit the linear blocks to the bit under the gantry and the rails to the table then the support will always be under the tool.
    You lose an unnecessary overhang.

    This is the document I was referring to.

    http://www.mech.utah.edu/~bamberg/re...e%20Design.pdf

    Page 176 onwards discusses Gantry designs. Mine was going to be a copy of their reference design. I agree, it looks wrong, however there is good data in this whitepaper .... did I misunderstand something?

  7. #17
    Don't let me stop you, we are all agog at that amazing pile of linear slides and waiting to see what you can make with them. Perhaps not Thor or Zeus, maybe Croesus
    Lots of pictures please

  8. #18
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 14 Hours Ago Has been a member for 4-5 years. Has a total post count of 973. Received thanks 69 times, giving thanks to others 42 times.
    Quote Originally Posted by Robin Hewitt View Post
    Don't let me stop you, we are all agog at that amazing pile of linear slides and waiting to see what you can make with them. Perhaps not Thor or Zeus, maybe Croesus
    Lots of pictures please
    Thanks. I am keen to ensure I dont waste what I have so open to all discussions around the design. If you have a few mins, please read the few pages in that whitepaper .... would love to know your (and others') feedback on the design. Originally, it started with an 'A' frame design. I changed it to suit the whitepaper design.

  9. #19
    I don't think I should comment on that white paper, it would be most unfair because I am an opinionated old git. Quite happy to comment on your design though, if you want me to

  10. #20
    Chaz's Avatar
    Lives in Ickenham, West London, United Kingdom. Last Activity: 14 Hours Ago Has been a member for 4-5 years. Has a total post count of 973. Received thanks 69 times, giving thanks to others 42 times.
    Quote Originally Posted by Robin Hewitt View Post
    I don't think I should comment on that white paper, it would be most unfair because I am an opinionated old git. Quite happy to comment on your design though, if you want me to
    You are free to do both.

    Ive learnt, with age comes experience, so you are more than welcome to comment. If I didnt want comments, I wouldnt have started the thread.

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