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  1. #13
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    Default Re: Yet another 3 axis CNC Router Design/Build

    PS: This one is by far one of the coolest minimalistic looking gantrys available.



    On the same channel is another video of it with a hexapod. Alien...



  2. #14
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    Default Re: Yet another 3 axis CNC Router Design/Build

    Quote Originally Posted by ger21 View Post
    The rigidity of the total assembly will have more to do with it than the bearing spacing. If the entire bolted assembly is capable of flexing at all, then you'll likely see some racking.


    While deflection may not be an issue, you might see vibration during cutting, which may have an effect on cut quality.

    Ok, I am thinking that I will start with a single centered ball screw drive for the gantry, but will make provisions to easily add a second ball screw (one on LH side and one on RH side) if the bolted assembly proves to not be rigid enough.

    Good point on vibration and chatter, yet another oversight. I think that I am going to start with what I have, I can add additional stiffening members under the table, as I do have extra room.

    Thanks



  3. #15
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    Default Re: Yet another 3 axis CNC Router Design/Build

    millhouse,

    I understand the advantages of the designs that you are suggesting, but I am thinking that the tall gantry plate design will suffice for my needs. Perhaps there will be a second build in my future with this type of design.

    The last video that you posted is one sweet looking machine. Thanks for sharing.



  4. #16
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    Default Re: Yet another 3 axis CNC Router Design/Build

    Update;

    Reduced gantry side plate height by 2.25".
    Designed z axis assembly with supported profile rails (6.5" of travel).

    What are people's thoughts on a counterbalance for the z axis?

    Yet another 3 axis CNC Router Design/Build-2018-10-26_1-jpg
    Yet another 3 axis CNC Router Design/Build-2018-10-26_2-jpg

    Attached Thumbnails Attached Thumbnails Yet another 3 axis CNC Router Design/Build-2018-10-26_1-jpg   Yet another 3 axis CNC Router Design/Build-2018-10-26_2-jpg  
    Last edited by daveysapps; 10-26-2018 at 07:36 PM.


  5. #17
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    Default Re: Yet another 3 axis CNC Router Design/Build

    Maybe you should switch to 25mm linear rails for the long axis. With the rails mounted at the sides the whole weight of the gantry pushes against only 1 row of the bearingballs so using bigger ones would be better.

    Your builds size is similar to my one (see attachment framesize 1000mm x 800m) and I used 25mm rails on all axis:

    I don't think that you "need" a counterweight but if you want to implement one you could use gas springs like the ones in the video of the minimalistic gantry or just a spring, mounted from the z backplate to the frontplate.

    Attached Thumbnails Attached Thumbnails Yet another 3 axis CNC Router Design/Build-bildschirmfoto-vom-2018-10-26-21-44-a  


  6. #18
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    Default Re: Yet another 3 axis CNC Router Design/Build

    20mm rails can handle several thousand pound loads. You won't be using 10% of their capacity.

    Yeah, no need for a counterweight on a little Z axis like that.

    Gerry

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

    Mach3 2010 Screenset
    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)


  7. #19
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    Default Re: Yet another 3 axis CNC Router Design/Build

    Looking at the specs, I thought that 20mm rails would be adequate.

    Thats x2 on not having a counterbalance for the z... good deal, one less component to design around.

    thanks folks!



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    Default Re: Yet another 3 axis CNC Router Design/Build

    I don't understand the benefit of using aluminum extrusion with steel bolted on the outside.

    Just use steel.

    7xCNC.com - CNC info for the minilathe (7x10, 7x12, 7x14, 7x16)


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    Default Re: Yet another 3 axis CNC Router Design/Build

    To cut down on the number of machined components, the thought is to use a table structure that is known to have a relatively good straightness tolerance ie extruded Al, and skin it with a material that is known to have a uniform thickness tolerance to create a planer surface for the rails to fasten to. A steel structure would require machining for flatness or an epoxy pour. I do not have economical access to machine long parts.

    Perhaps this isn’t the best approach, but it seams to be the best given the processes readily available to me.

    That being said, I would prefer to build the table out of steel...

    Last edited by daveysapps; 10-27-2018 at 09:46 PM.


  10. #22
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    Default Re: Yet another 3 axis CNC Router Design/Build

    Project update.

    Welded base
    Yet another 3 axis CNC Router Design/Build-welded-base-jpg

    Laser cut sheet metal

    Yet another 3 axis CNC Router Design/Build-laser-cut-sheet-metal-jpg

    80/20 machined

    Yet another 3 axis CNC Router Design/Build-machined-8020-jpg

    table assembly

    Yet another 3 axis CNC Router Design/Build-8020-assembly-jpg
    Yet another 3 axis CNC Router Design/Build-table-assembled-jpg

    Attached Thumbnails Attached Thumbnails Yet another 3 axis CNC Router Design/Build-table-assembled-jpg   Yet another 3 axis CNC Router Design/Build-welded-base-jpg   Yet another 3 axis CNC Router Design/Build-laser-cut-sheet-metal-jpg   Yet another 3 axis CNC Router Design/Build-machined-8020-jpg  

    Yet another 3 axis CNC Router Design/Build-8020-assembly-jpg   Yet another 3 axis CNC Router Design/Build-8020-assembly-2-jpg  


  11. #23
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    Default Re: Yet another 3 axis CNC Router Design/Build

    FYI, by no means do I consider myself to be a welder.



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