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  1. #1
    Join Date
    Jan 2014
    Posts
    50

    Fixed gantry vs moving gantry

    I would like to hear from people that have fixed gantry machines. If you've used both that would be great too. How do you like your machine? would you do it again?

    I can get steel for cheap, so having a fixed gantry is appealing. I could build it heavy & strong without having to worry about stressing out a single X axis motor

    Is it more difficult to secure the work piece to the table with a moving table?

  2. #2
    Quote Originally Posted by scott0999 View Post
    I would like to hear from people that have fixed gantry machines. If you've used both that would be great too. How do you like your machine? would you do it again?

    I can get steel for cheap, so having a fixed gantry is appealing. I could build it heavy & strong without having to worry about stressing out a single X axis motor

    Is it more difficult to secure the work piece to the table with a moving table?

    What size machine are you looking to build? Fixed gantry designs get rather unwieldy when you the movable table length gets really long. You have 2 types of fixed gantry designs. The first is like your typically mill in that the table moves in X and Y. I would not use this particular design if your travel dimensions are greater than 9"x20".

    There is also the design in which the gantry moves in the y and the table moves in the X. You have leeway to makd the Y axis pretty long. I would use that design for up to 18"x36" travel dimensions.

    Anything longer and making the gantry move makes more sense.

    As far as clamping the part it normally won't matter too much. We don't see too much of a difference.


    Nate
    Fine Line Automation
    www.finelineautomation.com
    Fine Line Automation
    www.finelineautomation.com

  3. #3
    Join Date
    Jan 2014
    Posts
    50
    Using SBR rails 800/500/300mm. With a moving gantry that would give ~ 22x13x6

    I would like the gantry to move the Y & Z, table just X.

  4. #4
    Quote Originally Posted by scott0999 View Post
    Using SBR rails 800/500/300mm. With a moving gantry that would give ~ 22x13x6

    I would like the gantry to move the Y & Z, table just X.
    Sounds like a really decent size for the fixed gantry setup. I think it will work out just fine.


    Nate
    Fine Line Automation
    www.finelineautomation.com
    Fine Line Automation
    www.finelineautomation.com

  5. #5
    Join Date
    Jan 2014
    Posts
    50
    Thanks for your input!

  6. #6
    Join Date
    Dec 2010
    Posts
    70
    Hello,

    Long time ago I also had my machine with fixed gantry but it design it to have the possibility to put it on linear blocks and change it into a moving gantry

    For Z-axis I like another design, especially for higher travels on Z, with 2 steppers which move the entire gantry's axis up and down. Some old pics here

    Good luck
    HTM.Ro - Hobby Tools Manufacturing

  7. #7
    Join Date
    May 2005
    Posts
    3920
    Quote Originally Posted by scott0999 View Post
    I would like to hear from people that have fixed gantry machines. If you've used both that would be great too. How do you like your machine? would you do it again?
    Don't have one at the moment but experience would tell me that a fixed Gantry design would be easier to get right and stiff.

    I can get steel for cheap, so having a fixed gantry is appealing. I could build it heavy & strong without having to worry about stressing out a single X axis motor
    The only real concern about steel would be the need to possibly (probably) have to have some machining done. If you have plenty of steel at your disposal then building strong shouldn't be an issue.
    Is it more difficult to secure the work piece to the table with a moving table?
    Every milling machine I've ever worked on had a moving table including some huge planner mills. Clamping reasonably sized pieces to the table will not be a problem.

  8. #8
    Join Date
    May 2005
    Posts
    3920
    Quote Originally Posted by FineLineAuto View Post
    What size machine are you looking to build? Fixed gantry designs get rather unwieldy when you the movable table length gets really long. You have 2 types of fixed gantry designs. The first is like your typically mill in that the table moves in X and Y. I would not use this particular design if your travel dimensions are greater than 9"x20".
    One shouldn't underestimate the issue of size as the machines get larger that is for sure.

    As for your limitation on the "mill" like machine I'm not sure why you cut it off at 9x20. A gantry makes it easier to do longer Y axis so 9" can easily be exceeded. I would personally lean towards the more traditional gantry as you indicate but I see that as personal preference.
    There is also the design in which the gantry moves in the y and the table moves in the X. You have leeway to makd the Y axis pretty long. I would use that design for up to 18"x36" travel dimensions.

    Anything longer and making the gantry move makes more sense.

    As far as clamping the part it normally won't matter too much. We don't see too much of a difference.


    Nate
    Fine Line Automation
    Home - Fine Line Automation

  9. #9
    Quote Originally Posted by wizard View Post
    One shouldn't underestimate the issue of size as the machines get larger that is for sure.

    As for your limitation on the "mill" like machine I'm not sure why you cut it off at 9x20. A gantry makes it easier to do longer Y axis so 9" can easily be exceeded. I would personally lean towards the more traditional gantry as you indicate but I see that as personal preference.
    I meant to say that I use 9x20 as a guideline. If I were designing a machine, I would transition to the fixed gantry with a movable table if I the x or y needed to be longer.




    Nate
    Fine Line Automation
    www.finelineautomation.com
    Fine Line Automation
    www.finelineautomation.com

  10. #10
    Join Date
    Apr 2009
    Posts
    5516
    Quote Originally Posted by scott0999 View Post
    I would like to hear from people that have fixed gantry machines. If you've used both that would be great too. How do you like your machine? would you do it again?

    I can get steel for cheap, so having a fixed gantry is appealing. I could build it heavy & strong without having to worry about stressing out a single X axis motor

    Is it more difficult to secure the work piece to the table with a moving table?
    No difference in how you fixture things, but heavier object might affect the performance of the machine. Otherwise, most all commercial VMCs and some high end commercial routers are built just this way.

  11. #11
    Join Date
    Jan 2014
    Posts
    36
    I think anything that is stable and movable will make sense.
    For Machinery Relocation, trust only Hanlon & Wright

  12. #12
    Join Date
    Jan 2014
    Posts
    50
    Thanks for all the replies

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