Need Help! Z axis coordinates inverted in MACH3 (down is positive)


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Thread: Z axis coordinates inverted in MACH3 (down is positive)

  1. #1

    Default Z axis coordinates inverted in MACH3 (down is positive)

    MACH3 newbie here...

    Well, as the headline states I think I have a problem with my MACH3 setup.
    This is retrofit of an old mill with propritary hardware and I have istalled an NVCMV2.1 USB controller and new stepdrivers. I have actually used the machine until now with GBRL and bCNC, but it is now converted to Mach3.

    Most is now in a working condition, homing works just fine and zero`s all the axis. X and Y axis is incrementing at "LEFT" and "UP", the problem is that Z is also incrementing at "DOWN". I am under the impression that the Z-axis is supposed to be negative when the tool moves down, like it did on my last GBRL setup. I have searched a lot on the web and all I can find is questions where folks is confused because the Z-axis is negative, opposite of my problem.

    This is not a direction problem of the stepper "DIR" signal. The Z-axis moves in the right direction. "Page Down" moves the tool closer to the surface. But while the tool moves down the DRO goes positive. I have tried multiple things to fix this. Direction in port setup only changes direction of the tool, obviously. I have even tried to adjust "Steps per" to "-400" (negative) in "Motor tuning", but this was not a plesant suprise.

    As far as I know is should be possible to change the setup in CAM-software to output g-code with inverted z-axis. But this is not the route I would like to go if I can avoid this.

    Is it possible to change this direction indication for the Z-axis?

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  2. #2
    Member lancut's Avatar
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    Default Re: Z axis coordinates inverted in MACH3 (down is positive)

    In Mach3 , go to 'config', 'Homing/Limits' and click on Z axis and select Reverse. Good Luck.

    My 2¢


  3. #3

    Default Re: Z axis coordinates inverted in MACH3 (down is positive)

    Thank you Iancut for the reply, but now I just realised how stupid I was for not beeing able to explain my question right. If I turn my direction in "Port setup" everything is actually OK, exept one thing. Then my problem is that my jogging is then upside down; "Page up" is tool down and "Page down" is tool up. Same goes for "MPG mode", "arrow up" (clearly labeled Z+) is tool down (Z-), and "arrow down" is tool up. But as I now write this down, I realize that this is may be the way it is supposed to be: that "Page up" and "Page down" is supposed to be the "work piece" going up and down relative to the tool, not the tool going up and down to the "work piece"?

    I now see that if I do like you suggest and reverse Z axis in "Homing/Limits" then it flips the scale and everything is in order exept for the Z-axis trying to home in the wrong direction (downwards). How can I then make it home in the positive direction without reversing Z-axis in "Homing/Limits" again?

    And please tell me, is "Page up" supposed to move the spindle up or the "work piece" up?

    Last edited by X10an; 04-19-2020 at 04:41 PM.


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    Member ger21's Avatar
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    Default Re: Z axis coordinates inverted in MACH3 (down is positive)

    Toggle the Home Neg setting in the home/limits page to change home direction.

    Page up should lift the tool up, away from the work, in the Z+ direction.

    The only other thing I can think of is that your X or Y axis is backwards, which might invert the coordinate system?

    Gerry

    UCCNC 2017 Screenset
    [URL]http://www.thecncwoodworker.com/2017.html[/URL]

    Mach3 2010 Screenset
    [URL]http://www.thecncwoodworker.com/2010.html[/URL]

    JointCAM - CNC Dovetails & Box Joints
    [URL]http://www.g-forcecnc.com/jointcam.html[/URL]

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)


  5. #5

    Default Re: Z axis coordinates inverted in MACH3 (down is positive)

    Quote Originally Posted by ger21 View Post
    Toggle the Home Neg setting in the home/limits page to change home direction.

    Page up should lift the tool up, away from the work, in the Z+ direction.
    Thank you, both of you. Combined you solved my problems.
    The "Reverse" of Z axis in "Homing/Limits" put my coordinates in the right direction, and the "Home Neg" put my homing back in the right direction. Part of the problem was that I did not see and/or know of the "Home Neg"-option, because part of the text was hidden by the cropped text-box. In my page it only displayed "Home..."
    Z axis coordinates inverted in MACH3 (down is positive)-screen-jpg



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Z axis coordinates inverted in MACH3 (down is positive)

Z axis coordinates inverted in MACH3 (down is positive)