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  1. #1
    Join Date
    Jan 2008
    Posts
    1523

    Fix it! (Moving to fixed gantry)

    Hi all. I built a moving gantry router primarily out of MDF over the past 6 months. My own design, which was probably a bit ambitious. Now I am left with a machine that works... but is not square, nor rigid.

    Parts I have:
    16mm supported rails: 1100mm, 600mm, 300mm
    1605 Ballscrews: 1100mm, 600mm, 300mm
    Chinese 1.5kw spindle + VFD
    Gantry bridge: 80x80mm aluminium extrusion 610mm long.


    My concept is fairly simple:


    The 1100mm rails bolt straight on to 30x60mm extrusion with 2 (or 3) cross beams.
    Then some short length of 30x60 stick out. On to these bolt 60x60mm gantry uprights.
    The extrusion will be joined by bolt in slot into tapped end + some corner brackets.
    The gantry beam is then attached these with a bracket (not pictured) - this is the main problem with the design, obviously not as strong as gantry beam sitting directly on the uprights. However, unless I want to get rid the $50 piece of metal I have all set up with rails and replace it with a longer piece (which I'd do from 60x60, therefore need nuts etc adding to the $$$) then I'm stuck with this.
    Also not pictured is bracing for the uprights in the X axis plane. I picture that this can be done very cheaply with sheet bolted to the outside of the uprights (triangle shape) with a free edge 'resting' on the table holding the machine.

    Thoughts?
    Load of crap?

  2. #2
    Join Date
    Apr 2009
    Posts
    5516
    Quote Originally Posted by pippin88 View Post
    Hi all. I built a moving gantry router primarily out of MDF over the past 6 months. My own design, which was probably a bit ambitious. Now I am left with a machine that works... but is not square, nor rigid.

    Parts I have:
    16mm supported rails: 1100mm, 600mm, 300mm
    1605 Ballscrews: 1100mm, 600mm, 300mm
    Chinese 1.5kw spindle + VFD
    Gantry bridge: 80x80mm aluminium extrusion 610mm long.


    My concept is fairly simple:


    The 1100mm rails bolt straight on to 30x60mm extrusion with 2 (or 3) cross beams.
    Then some short length of 30x60 stick out. On to these bolt 60x60mm gantry uprights.
    The extrusion will be joined by bolt in slot into tapped end + some corner brackets.
    The gantry beam is then attached these with a bracket (not pictured) - this is the main problem with the design, obviously not as strong as gantry beam sitting directly on the uprights. However, unless I want to get rid the $50 piece of metal I have all set up with rails and replace it with a longer piece (which I'd do from 60x60, therefore need nuts etc adding to the $$$) then I'm stuck with this.
    Also not pictured is bracing for the uprights in the X axis plane. I picture that this can be done very cheaply with sheet bolted to the outside of the uprights (triangle shape) with a free edge 'resting' on the table holding the machine.

    Thoughts?
    Load of crap?
    Seems like you can make your table a lot narrower, since your gantry travel would be the length of the rail minus the width of your carriage? Would make you gantry stronger.

  3. #3
    Join Date
    Mar 2003
    Posts
    35538
    Quote Originally Posted by pippin88 View Post
    Also not pictured is bracing for the uprights in the X axis plane. I picture that this can be done very cheaply with sheet bolted to the outside of the uprights (triangle shape) with a free edge 'resting' on the table holding the machine.

    Thoughts?
    Load of crap?
    I don't think that the triangles resting on the table will increase rigidity at all. They need to be fastened to the tubes under the table.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

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    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  4. #4
    Join Date
    Jan 2008
    Posts
    1523
    Quote Originally Posted by louieatienza View Post
    Seems like you can make your table a lot narrower, since your gantry travel would be the length of the rail minus the width of your carriage? Would make you gantry stronger.
    louie: My lower Y rail runs on the underneath of the gantry beam. This means I can't get the uprights under the (current) beam. Changing the work table size won't change that unfortunately.

    Quote Originally Posted by ger21 View Post
    I don't think that the triangles resting on the table will increase rigidity at all. They need to be fastened to the tubes under the table.
    Gerry: I should have been clearer, the braces would rest on the benchtop, not the work table. I'll CAD it up tonight.

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