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  1. #11
    Maybe this extra stiffness of the box section is why the likes of axyz and chinese makers use this design for the y axis?
    Do they use aluminium or mild steel box section. I bet its steel, stronger and easy to weld plates onto it as well as better stiffness?
    what is the main reason diy builders use aluminium, softer so easier to machine, lightness or does not rust?
    Any ideas?
    I am not American!

  2. #12
    Hi williamturner1

    You might be reading off the wrong rows.

    I've compared the 2 shape:
    'I beam' width 100mm, depth 200mm, flange 10mm, web 7mm
    RHS width 120mm, depth 80mm, wall 3mm

    Assuming length 2000mm, and your weight 60kg, and vertical Z deflections are:
    I beam 23 microns
    RHS 393 microns

    Which tallies with your jumping experiment, showing the vertical stiffness difference, where the I beam is much stiffer.

    Unless you had a lever arm to jump on (which was very stiff), then you would not be comparing the torsional performance which I would expect to be worse for the I beam.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  3. Thanks for sharing your info. Here is a great paper on torsion of beams. The clear winner is closed shapes, tubes, of all shapes: circular, rectangular.
    I'm in the process of beefing up my aluminum extrusion CNC to be a dual-purpose wood/metal machine and have so much to learn. This is a great forum! If any of you would care to view this video and lend some advice, I'd sure appreciate it.

  4. #14
    Hi Tyler

    Welcome to the forum. You may find the picture build menu interesting

    Note the suggested rules of no replies just to keep that thread clean, but see if there is something there. The posters are regulars here so start a new thread with questions for more info on any of the machines.

    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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