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  1. #41
    View from front looking at current gantry design.



    This is for the open-bed style table with the longer gantry arms. The linear guides can be easily covered from the top.

    The gantry beam will pass through the side support plates and be welded up and gusseted inside with some nicely cut parts, the outer face of the vertical supports can be strengthened with a couple of ribs to resist side-sway.

    Mounting the support rails is harder on the open bed style though, I was going to bolt them on but this style really wants a box frame at bed level.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  2. #42
    Every action has an equal and opposite reaction. If you apply 300N accelerating force to the cutting head, the gantry will push sideways with 300N.

  3. #43
    Yes I can remember that from school ;)

    But those 300N can be countered by applying gusset plates and ribs where needed, most tend to throw a slab of alu at it but that might not be totally needed i think.
    Last edited by Davek0974; 30-06-2015 at 05:02 PM.

  4. #44
    Or you could move the rails up closer to the gantry they support. The gantry only needs to be 2" above the bed, doesn't it?

  5. #45
    In theory yes but my Z-axis needs a bit of clearance as its a pretty heavy built unit. I am trunk not to lift the rails - that was design idea one, but it means you do not have a clear open bed - you have rails either side which makes loading harder especially if juggling a bigger sheet on your own.

    My high-rail option is sketched out earlier, it had no risers at all on the gantry - the beam was right down on the carriages.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by Davek0974; 01-07-2015 at 06:24 AM.

  6. #46
    Quote Originally Posted by Robin Hewitt View Post
    Or you could move the rails up closer to the gantry they support. The gantry only needs to be 2" above the bed, doesn't it?
    To add scale to my poor sketches, the bottom of the gantry beam is 140mm above the bed surface, not too bad??

  7. #47
    Ok, stuff is on order.

    The final result is 50x50x2 for the gantry beam and frame legs, 50x80x2 for the motion support/bed frame.

    The final capacity is going to be the half sheet 1250x1250 / 4'x4' size.

    Direct drive rack and pinion with a view to change to belt reduction drive or even ballscrews later on.

  8. #48
    Good man thats what like to see no messing around.

  9. #49
    Quote Originally Posted by JAZZCNC View Post
    Good man thats what like to see no messing around.
    Oh I can mess around, to a point, then I just dive in and go for it.


    The top box is the gantry beam, 50x50, the motor sits down the bottom on a plate that swivels on the point shown. It will be spring loaded but restricted so it cannot jump out of the rack and chew it up.

    A couple of 75mm gusset plates under the beam on the inside and a rib or two on the outside should stiffen things up a fair bit.

    Motors, controllers and rack arrived today :)
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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  11. #50
    Steel came Friday, nice and straight and after a few stress tests (me standing in the middle of a 7m long beam) I realised just how rigid this stuff is

    Construction question:

    I was thinking of welding on some 100x50x10mm pads under each corner of the motion frame and similar to the top of each leg, then bolting the two parts (welded motion frame/bed and welded leg assembly) together, just to give the opportunity to shim out any variation in leg length etc. Good idea, bad or not worth it???

    Next, the bed/motion frame - should I attempt to weld it up as one piece, or weld closing plates flush into the ends of the cross-members, drill/tap and then bolt together?? If yes then how to weld the closer plates in - only way i can think is to heavily bevel the plates then insert and fill bevel with weld tying into the tube sides??? Plates would be 46x76x10mm.

    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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