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  1. #1
    Well I did say I would be asking questions..... , this is my first machine build, reading the various build threads has given a lot of inspiration, hopefully enough to get the design right with a little (lot!!!) of help. This is a DIY "at home" project, and am looking to minimise any external machining etc. so lathe and hand tools mainly

    Base for router, mainly wood, if I can get design right then a small amount of non ferrous as well (would be nice for small parts)

    work table is 900 x 800 and about 220Z, so am expecting about 900x 700mm max machinable width, overhangs on rails sufficient to maximise work area and allow edge drilling at one end, clean pass through to allow longer if required

    Structure is 50x50 and 100x 50 steel box, welded. Support rails for linear track is bolted to allow alignment with epoxy putty or shims between plates and if required tig brazed/tacked to secure. Ends are bolted on to improve rail stability and allow adjustment, bolted in place and the drilled & reamed for pins.




    To me this feels over engineered..

    any thought, suggestions or observations gratefully received
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  2. #2
    It looks a lot like my frame, but, there was quite a bit of discussion regarding where to place everything and I'll try to list them all;

    1. don't position diagonal tubes right in the corners.
    2. don't bring two diagonal tubes together in a point at the top
    3. don't attach parts directly in line with other parts
    4. diagonals across the bottom will remove the need for small corner braces in the bed

    At the moment you have no support around the edges of the bed but if you rotate the 100x50 you will.
    Don't use that supported rail, it's nowhere near as good as Hiwin type rails.
    You might want to put adjustabe feet on the legs.


    You can see what I mean by looking at one of these photos; http://www.mycncuk.com/threads/6565-...4294#post54294
    Last edited by EddyCurrent; 15-12-2014 at 08:31 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  3. #3
    thanks Eddy...more questions..

    1, diagonals into corners why not?, ditto connecting 2 at the middle (sorry, I am one of those people that like to understand the why)
    3 I get as it eliminates resonance... easier to draw symmetrically for this stage...
    Bed support is not a problem... just no need to show for the frame development... it will be there when made
    feet will be on a level pad and shimmed and bolted down

    Re rails... I have been looking for some real comparative data.... (similar to the info on round vs supported rails on the forum) from what I can find... only looking as I wont be buying for a while... profile rails & bearings seem to be about 2x the cost of supported rails ( 20mm supported compared to 15mm profiled but I am guessing I will want 20mm? which puts it nearer 3x) ie I need info to justify the additional cost (in all likelihood I would end up that way anyway, these were the first 3d model that I found & thought "hell that will do for development, regardless of what I eventually use)

  4. #4
    Quote Originally Posted by mike os View Post
    thanks Eddy...more questions..

    1, diagonals into corners why not?, ditto connecting 2 at the middle (sorry, I am one of those people that like to understand the why)
    Jazzcnc
    Be careful when welding the diagonals where they meet in the centre, don't weld both at same time has you'll be putting a lot of heat in one spot.
    I assumed same might apply to diagonals in the corners, also it was suggested by silyavski to put the diagonals so they were about 1/3 way up the legs and also supported the upper rail at more places than just the centre point so I put them at 45 degrees which spread them across the upper rail but not at the same place as the short upright stubs supporting the linear rails beam.
    Last edited by EddyCurrent; 15-12-2014 at 10:44 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

  5. The Following User Says Thank You to EddyCurrent For This Useful Post:


  6. #5
    Assuming that the base is basically OK.... will update drawings in final draft for asymmetric layout

    What is a reasonable weight for a gantry given the OP? planning on steppers for drive, I guess 2 rather than 1 and belts.
    ballscrews or rack for Z.... or does it make little difference at this size

    been playing in steel, bolted/glued rather than welded as I don't want to have to take it to be machined & weight seems very excessive...

    I am Aiming for about 240mm spacing on y rails and at least 150-200mm on z, does this seem about right?
    Last edited by mike os; 17-12-2014 at 05:56 PM.

  7. #6
    playing with gantrys... please ignore drawing errors....just reused parts to get some ideas together

    1, steel, with welded beam (100x50 box), 4/6mm brace. Ends & bearing carriage are 10mm bolted and tacked or TIG brazed if necessary and bolted to gantry beam. gantry approximately 930 wide, weight approx. Mass approx. 52kg
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  8. #7
    Gantry 2
    Still all steel, this could be fully bolted, which eliminates any heat distortion issues, again can be TIG tacked or TIG brazed if necessary
    A little heavier, but easier to ensure no distortion and should be a lot stiffer? however this weighs in at 66kg!!!
    Cant help feel that is getting a bit much, but I really don't know
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    Last edited by mike os; 19-12-2014 at 09:34 PM.

  9. #8
    Gantry 3

    Steel ends, aluminium box and plate gantry beam, all bolted
    This checks in at a more reasonable 40kg
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  10. #9
    Am I worrying too much over the weight?
    Which design is heading in the right direction? or am I going the wrong way?

    on all the above the COG is low and just forward of the middle of the gantry beam

  11. #10
    Only the first version has a space for the Y ball screw I think. One good thing about aluminium box section is that it's quite accurate dimension wise, I put my rails top and bottom and using a vernier the distance between them was the same right across the gantry.
    Last edited by EddyCurrent; 19-12-2014 at 10:00 PM.
    Spelling mistakes are not intentional, I only seem to see them some time after I've posted

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