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  1. #1
    Hello all!

    I'm writing to you from snowy Estonia. This forum is absolutely brilliant! Totally inspiring to all future machinist!
    Like many others I've been reading this forum and sucking up information for DIY CNC machines. Im a production engineer for fine mechanics and all-around handyman in spare time.
    I dont have any real purpose for a CNC machine! Am I the only one here with that problem? :)
    For sure it could help out with my projects and so on but I don't have any business plan and don't know how the investment will pay off. The goal is to use materials I have and build the best machine possible. Quite original idea...

    My first plan was plasma cutter/wood router. But laser and plasma cutting is easily accessible in other companies and also the hassle with big format metal sheets is not for me. And as I kept reading this forum it became clear to me that this cheaply built plasma CNC would really suck at machining wood. So I folded this idea.
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    Next in line was serious wood router for big format 1250x2500 timber sheets. With possible precise aluminium options. Design came up like this. Aluminium gantry, adjustable bed, eopxy leveling and HIWIN rails.
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    But could not really see much work for large wood sheets and it would suck at precise aluminium. So folded again.

    I have some small stepper motors and availability to get great price thick aluminium plates and steel profiles. So now the idea is to build fixed gantry, super rigid and suitable for at least aluminium/hard materials. Precision is the goal here. I would love the idea of machining steel but its not easily achievable with Chinese WC spindles - I will investigate alternative spindles for that.
    Here is the latest version: 4x100x100 steel frame, welded, epoxy leveled X and Y, 20mm aluminium Z-axis, HIWIN 20 rails, 1605 ballscrews all axis, timing belt drives, aluminium bed with fluid collector, 460x500x200mm.
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    Please dont hold back your comments! Steel frame in the picture is probably 3rd version. Still dont like it. I think its rigid enough but although Im good welder it is still complicated and lacks of adjustment options. I will probably separate the frame to lower and upper part. Mybe someone can point me to genius simple fixed gantry frame designs? ;)
    Another issue is with x-bed design. It is designed with aluminium material dimensions that is accessible to me. Fastened with countersunk screws. Could this work or needs more support?
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    Hope that sharing my project will boost my motivation and also fill my brain with simple and ingenious solutions. I wish this for all readers as well!

    PS. All designs here are not complete and lack small details as fasteners, belts and so on...

  2. #2
    Hi,

    Sensible thinking on the others and credit to you for doing research before jumping in and having ago your self with design, wish others would do the same.!

    Your design like you say is a little restrictive and complicated around the backside but it's not too far away.

    Now for a long time I've been going to make something similair thou slightly larger but with a slightly differant design that in my opinion if done correctly will give best possible amount of strength at the tool where it's needed.
    Now I've seen a few machines done in this way before but other day found this on youtube which will show you what I mean.

    As you'll see the Gantry lifts not the Z axis. This gives some very serious advantages where it matters at the tool because your getting maximum support from the Gantry at the spindle with No Z extension so only extension from the Spindle is the tool length the chatter is greatly reduced. This allows either better finish or deeper/faster cutting or some of both.

    The machine in the video could be done better regards the frame and it's got a crappy spindle on it so not showing it's true potential but it will show exactly what I mean.

    If the frame was beefed up and Gantry counter balanced to allow faster Z movements plus take some of the strain of motors etc and obviously put a real spindle on it not a toy then IMO it would be a cracking little machine.

    Last edited by JAZZCNC; 21-03-2014 at 04:00 PM.

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  4. #3
    Very interesting design. Have not seen this approach yet.
    What do you exactly mean by counterbalance?
    First thing that pops into my mind is to add 2x rails for Z-axiz to other side of the gantry(cost and alignment issue). And maybe move spindle closer to center line of the gantry. But maybe move Z rails on the sides of the gantry at all...
    I will put it on the canvas.

  5. #4
    Quote Originally Posted by toomast View Post
    What do you exactly mean by counterbalance?
    Well the name says it all really but how you go about achieving it depends on design.! You can use Gas struts or simple counter weight on rails like you mention.
    Last year I nearly bought a large-ish Industrial 5axis VMC overhead gantry machine that had a long heavy Z axis which used simple counter weight on round type linear rails running down the back with a pulleys at the top, just like the Old sash windows.!! Simple an affective with very little setup, aliagnment wasn't critcal.



    Quote Originally Posted by toomast View Post
    And maybe move spindle closer to center line of the gantry.
    Not understanding you here.? Spindle Nose will determine it's location on Gantry or Plate it fastens on, you won't want the collet nut any higher than the lower edge of the mounting plate.!

    Quote Originally Posted by toomast View Post
    But maybe move Z rails on the sides of the gantry at all
    Again not understanding.? Why move the rails on the gantry.? Nothing to be gained doing this.!

  6. #5
    And almost a hole year later I am back. Despite not posting I have frequently visited forum and learned a lot more. Mean time some fantastic build logs have completed which have sent my mind wondering...

    This is my fixed gantry next revision. Frame design is more clear and simpler now. Z is counterbalanced with gas struts. I decided not to limit my design with the random components I have. In near future I have possible projects for this machine - so then I can review the hole design and make needed changes in workarea or something else.


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  7. #6
    Thats looking excellent and will be a very strong capable machine. Only thing I see that you dont show is any scope for adjustment between the moving table rails and the gantry upright rails.? (Or is that why the moving table frame is blue.?) They need to be perfectly perpendicular to each other.!

    You wont easily achive this welding the frame so you need some form of adjustment building into the machine. !! PLENTY OF ADJUSTMENT IS THE KEY TO GOOD DIY BUILD.!! . . . I say this in CAPITALS because it's often missed and then regreted later.

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  9. #7
    The blue frame is separate from main frame and therefore adjustable. For now I`m not sure how the adjustment and rigid fixating of the bed frame will look like...

    Welding the big frame together will take some time but. Wonder if there is any point creating subassemblys and bolt them together?...there is not any adjustment needed if I epoxy level gantry upright rails and bed frame is adjustable. It will be heavy fo sure.

  10. #8
    In search of a better/simpler/cheaper design I have come up with these versions. As pictures illustrate I did not succeed.





    For the time being this fixed gantry design will come to a halt. As I have a need for larger work area and more general machine. Probably will go with something similar to Syliavski`s design.
    This project is published in https://grabcad.com/library/fixed-ga...nc-460x500mm-1
    Thanks for listnening!
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  11. #9
    It still looks a tadge wrong to me...

    I thought the big advantage of the fixed gantry was that you could localise the support for the bed where it was needed. You put your rails on the bottom of the bed and your linear blocks under the gantry. There is no point in supporting the bed anywhere but under the gantry, you are just introducing unnecessary overhangs

    The machine should appear as a gantry with a bed sliding through it
    Last edited by Robin Hewitt; 11-06-2015 at 09:03 AM.

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  13. #10
    Quote Originally Posted by Robin Hewitt View Post
    It still looks a tadge wrong to me...

    I thought the big advantage of the fixed gantry was that you could localise the support for the bed where it was needed. You put your rails on the bottom of the bed and your linear blocks under the gantry. There is no point in supporting the bed anywhere but under the gantry, you are just introducing unnecessary overhangs

    The machine should appear as a gantry with a bed sliding through it
    It is not perfect :)
    I don't quite follow you though.
    Do you mean fixing HIWIN rails to moving bed and bearing blocks to main frame?

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