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  1. #1
    Sterob's Avatar
    Lives in Australind, Australia. Last Activity: 16 Hours Ago Has been a member for 0-1 years. Has a total post count of 68. Received thanks 4 times, giving thanks to others 4 times.
    I am looking at the possibily of changing my design to a Fixed Gantry type machine.

    Are there any Golden Rules for designing this type of machine?

    ie Location of Gantry on the frame or the length of ball screws needed to obtain full ned travel. that sort of thing?


    If my question is too vague, apolagises...I am just trying to learn the best way, to save re-work.


    Steve

  2. #2
    IMO its good for max 60x40cm machines. 60x90 machine i wouldnt make fixed gantry
    project 1 , 2, Dust Shoe ...

  3. #3
    Quote Originally Posted by Boyan Silyavski View Post
    IMO its good for max 60x40cm machines. 60x90 machine i wouldnt make fixed gantry
    Why Size of the machine as nothing to do with it.!
    If you have the extra space it requires then a fixed gantry will always be stiffer than a moving gantry by the simple fact your not having to deal with a moving Mass so can build it stronger with no penalty other than extra length.

    Some of the largest CNC machines in the world are Fixed Gantry machines.!
    -use common sense, if you lack it, there is no software to help that.

  4. #4
    Quote Originally Posted by JAZZCNC View Post
    Why Size of the machine as nothing to do with it.!
    If you have the extra space it requires then a fixed gantry will always be stiffer than a moving gantry by the simple fact your not having to deal with a moving Mass so can build it stronger with no penalty other than extra length.

    Some of the largest CNC machines in the world are Fixed Gantry machines.!
    Isn't it a bit strange for a 1m table to move back and front? it seems too long
    project 1 , 2, Dust Shoe ...

  5. #5
    Kitwn's Avatar
    Lives in Exmouth, Australia. Last Activity: 4 Hours Ago Has been a member for 2-3 years. Has a total post count of 465. Received thanks 62 times, giving thanks to others 11 times.
    Quote Originally Posted by Boyan Silyavski View Post
    Isn't it a bit strange for a 1m table to move back and front? it seems too long
    Surely you'd make the long axis the fixed one in this instance? No problems in building a rigid gantry with 900mm travel.
    Engineering is the art of doing for ten shillings what any fool can do for a pound.
    Wellington.

  6. #6
    Sterob's Avatar
    Lives in Australind, Australia. Last Activity: 16 Hours Ago Has been a member for 0-1 years. Has a total post count of 68. Received thanks 4 times, giving thanks to others 4 times.
    Yes, I'd be moving the shorter distance of the table, ie 480mm so I need ~ 900mm rails and balls crews for that axis

  7. #7
    The other reason i dont like long and wide for that matter Fixed gantry, is that the table that moves has to ve sturdy and the only solution there is a very expensive aluminum plate, while you can throw anything you have at hand for the bed . Also a protection should be done for the ballscrews

    And as the table grows, the motors will grow and the machine will grow slower.

    Not a problem though if you will be cutting metal mainly

    I still believe the Z is the most important thing, not only the gantry , if gantry properly made. And i can prove it to anybody how a 2 meter wide gantry cuts up to mild steel with mirror like finish. And aluminum like butter.
    project 1 , 2, Dust Shoe ...

  8. #8
    Quote Originally Posted by Boyan Silyavski View Post
    The other reason i dont like long and wide for that matter Fixed gantry, is that the table that moves has to ve sturdy and the only solution there is a very expensive aluminum plate, while you can throw anything you have at hand for the bed . Also a protection should be done for the ballscrews

    And as the table grows, the motors will grow and the machine will grow slower.

    Not a problem though if you will be cutting metal mainly

    I still believe the Z is the most important thing, not only the gantry , if gantry properly made. And i can prove it to anybody how a 2 meter wide gantry cuts up to mild steel with mirror like finish. And aluminum like butter.
    It's all a matter of degree of difficulty and expense.!. . . .Give me enough money and I could build you a Fixed or moving gantry 5 axis machine with 20Mtr travels that will cut titanium like butter.!! . . . The simple fact is that a Fixed gantry will always be stronger because it can be over engineered with less cost in terms of effect on performance and component cost. Downside is it takes much more room.

    Your Machine Boyan is a credit to you, but it's massively over engineered for what it's doing which cost's extra money that isn't really required. It's also well beyond what most people can achieve in there little sheds or garages with limited tools. Some people don't want to pay for a whole machine much more than what you paid for the 3mtr straight edge.!!

    A fixed gantry machine is a good choice if you have the room as it allows you to get high strength without having the expense of building a very strong and heavy moving gantry which requires bigger better motors etc.
    -use common sense, if you lack it, there is no software to help that.

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