Alignment issus?


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    Default Alignment issus?

    I've been trying to square my gantry to my table and also verify that it cuts properly and squarely. I'm running into an issue with the squareness - when I take a measurement diagonally to check that my cuts are square they are off by 3/16 but the length and width measurements appear to be the same, any ideas on what might be going on, I didn't think that was mathematically possible?

    I'm not sure how the length and width are identically but the diagonals are off?

    I've attached the gcode and drawings I'm running just for the sake of someone else taking a look to make sure its correct, looks right to me.

    I'm a little stumped.. thoughts or ideas???

    Adam,

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    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Community Moderator ger21's Avatar
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    when I take a measurement diagonally to check that my cuts are square they are off by 3/16 but the length and width measurements appear to be the same, any ideas on what might be going on, I didn't think that was mathematically possible?
    That's known as a parallelogram, I believe. Yes, it's possible. It means you're gantry isn't perpendicular to the other axis.

    You didn't post your g-code, but the drawing looks fine.

    Gerry

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    Gold Member LeeWay's Avatar
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    3/16" out of square is actually quite a bit. That would be the same amount that the gantry is out of square by I would think. It kind of depends on the machine as well though. Different solutions for different mechanical layouts and drive systems.
    On my plasma machine that has a slaved motor for one side, I would simply slide my home switch forward by 3/16" on the side that was off. That would allow it to cut square after homing.
    On my first router, it has a single ball screw. Each side of the gantry has adjustments built in. I would loosen and tighten sides to achieve the squareness I needed.

    What type machine do you have?

    Lee


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    Thanks Gerry,

    So, I assume that's the X to the Y axis?

    Since I'm homing my X and A separately to square it to the table how do I get rid of the alignment issue, not 100% on the fix?

    Here is the gcode in a .txt format, the NC file is the gcode.

    Adam,

    Attached Files Attached Files
    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Quote Originally Posted by LeeWay View Post
    3/16" out of square is actually quite a bit. That would be the same amount that the gantry is out of square by I would think. It kind of depends on the machine as well though. Different solutions for different mechanical layouts and drive systems.
    On my plasma machine that has a slaved motor for one side, I would simply slide my home switch forward by 3/16" on the side that was off. That would allow it to cut square after homing.
    On my first router, it has a single ball screw. Each side of the gantry has adjustments built in. I would loosen and tighten sides to achieve the squareness I needed.

    What type machine do you have?
    I agree, 3/16 is a lot. I would be more comfortable if it also showed up in the length and width measurements...

    I believe our machines would be similar in design, 3 axis design, I have a slave axis "A" on my "X" axis.

    Maybe I'm thinking about this incorrectly, moving the A or Z axis independently forward or backward should square it up? At that point how do you also square it to the table, maybe that doesn't matter.. not sure.

    Thanks,

    Last edited by adam_m; 02-15-2014 at 12:48 PM. Reason: add image
    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Quote Originally Posted by LeeWay View Post
    3/16" out of square is actually quite a bit. That would be the same amount that the gantry is out of square by I would think. It kind of depends on the machine as well though. Different solutions for different mechanical layouts and drive systems.
    On my plasma machine that has a slaved motor for one side, I would simply slide my home switch forward by 3/16" on the side that was off. That would allow it to cut square after homing.
    On my first router, it has a single ball screw. Each side of the gantry has adjustments built in. I would loosen and tighten sides to achieve the squareness I needed.

    What type machine do you have?
    I agree, 3/16 is a lot. I would be more comfortable if it also showed up in the length and width measurements...

    I believe our machines would be similar in design, 3 axis design, I have a slave axis "A" on my "X" axis.

    Maybe I'm thinking about this incorrectly, moving the A or Z axis independently forward or backward should square it up? At that point how do you also square it to the table, maybe that doesn't matter.. not sure.

    Thanks,

    EDIT

    After viewing an image of a parallelogram I realize that the math does make sense and that it should be an adjustment to the gantry A or X axis.

    Do I move the axis into the long side or the short side?

    Attached Thumbnails Attached Thumbnails Alignment issus?-snag-0002-png  
    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Gold Member LeeWay's Avatar
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    Once you have the machine cutting squarely, then that is the new table. You would square a sacrificial table to the machine as it is when cutting squarely.
    The home switches on my plasma are pretty easy to adjust.
    I just loosen the plates and slide them forward or back. The arm is also adjustable on these switches which makes it dead simple to adjust easily to fine tune a side.




    Lee


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    Gold Member LeeWay's Avatar
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    It depends on which switch will be the easiest for you to move. Either side will basically accomplish the same thing, but moving one side will shorten the overall travel on the machine. Also remember that moving half the distance to correct 3/16" squareness fault would mean moving the switch 3/32" or so. Then recheck.

    Lee


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    Community Moderator ger21's Avatar
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    Yeah, it depends on which end your switches are mounted, and home much adjustment they have.

    In your above example image, the corners are labeled A,B,C,D. Move one switch like your dragging a corner of the image to make it a square.

    Gerry

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    Many thanks for the posts, I think I got it square.. strange thing is that I had moved the switch before on the "A" axis but must have inaccurately measured after running the gcode.. go figure!

    Adam,

    G540, Rack and Pinion Drives-X/Y axis, 1/2-Ball Screw-Z Axis w/THK HSR 25 Linear Slides, Steppers KL23H2100-35-4B, Power Supply-KL-600-48


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    Gold Member LeeWay's Avatar
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    It's good to test it out every so often. On my plasma, I use a die grinder with a carbide drill mill for engraving the sheets.
    I line up a known square sheet against my X axis rail and then just jog my Y along the other edge of the sheet. Takes only a few seconds for peace of mind.

    Lee


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Alignment issus?

Alignment issus?