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Zero machine / work and homing

Discussion in 'Control Software' started by J-P, Feb 20, 2020.

  1. J-P

    J-P New
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    I'm trying to find information on how to configure the limit switchs and how to zero. I really like the Blackbox hardware and Control software, but the software seams to lacks a good manual.

    Here are the points I need help clariying/solve...:
    1. I found the "Home All" button, but can I home a single axis?
    2. After homing and moving somewhere, if I click any gotozero button (xyz, x, y, z), when it reach zero, it triggers a limit switch and raise an alarm and stops everything... why so? and how to solve that. For info, my limit switches are Xmin, Ymin and Zmax.
     
  2. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Negative, by default Grbl only has the $H all axes command (though you can custom compile a version that can do single axis homing, and then send individual commands using serial console)
    However, We don't see the need. Home once after power up to establish machine coordinates. For that to work you need to home all axes anyway. From there offsets (work coordinates) can be set per-axis

    You need to tell it where the safe work envelope in the Work Coordinate system is, by jogging to where zero should be, then clicking Setzero
     
  3. romamaker

    romamaker Well-Known
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    For #2, you've got to set your zero point manually. Homing the axis doesn't set the zero, nor is the "home" position for the axis necessarily where you want the zero point to be. (The limit switches are really more of just a safety net then anything else, to make sure you don't accidentally slam an axis into a hard limit.) You manually jog to where you want the Zero point to be, then hit the "setzero" button. Then, after you move around, "gotozero" will return your zero point.

    Edit: Whoops, Peter beat me to it!
     
    #3 romamaker, Feb 20, 2020
    Last edited: Feb 20, 2020
  4. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    That, and "reestablish all saved offsets by rehoming" means you can store things like your Work Zero through power off, etc by just Homing again, it will get all those back to the same physical space (G28, G30, any G92 offsets, all the Coordinate systems, etc all reference off the Machine coordinates (Mpos+offset=wpos for example)

    Sorry! But extra confirmation never hurts!
     
  5. Dina Jacobson

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    LEAD 1010 machine, high Z mod, 2 X, 2 Y and 1 Z limit switch.
    All limit switches work good when homing all, but
    I would like to be able to home X & Y axii separately.
    I'm automating datum setups etc... and need to be able to
    set machine to limit switch locations separately otherwise I
    would crash into parts on the table.
    Using 3 different axis configurations for different assemblies.
    Currently using openbuilds control, but eventually will be controlling with labview.
     
  6. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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  7. Dina Jacobson

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    oh boy, thanks sounds like fun :)
    so for the blackbox I can compile new firmware to flash with the arduino program?
     
    #7 Dina Jacobson, May 19, 2022
    Last edited: May 19, 2022
  8. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Yes, it runs the same Arduino Uno core
     
  9. Dina Jacobson

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    got it !!! :)
    Awesome
     
    #9 Dina Jacobson, May 20, 2022
    Last edited: May 20, 2022
  10. Dina Jacobson

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    @Peter Van Der Walt so what exactly in labview needs to be modified?
    "modify the Labview code".
    I am currently opening and sending commands via visa vi's.
    Thank you for your help :)
     
  11. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Well, Labview probably sends "$H" for homing
    To do that, you cannot use $H anymore - as that "homes all axes" - not seperately as you wanted to do

    As per grbl/config.h at bfb67f0c7963fe3ce4aaf8a97f9009ea5a8db36e · gnea/grbl - the homing commands for seperate homing are:

    Code:
     Enables single axis homing commands. $HX, $HY, and $HZ for X, Y, and Z-axis homing. 
    So, I am assuming you'll need to apply some modification to Labview to send $HX/$HY/$HZ at relevant times rather than sending $H which is the Grbl default. Not familiar with Labview myself, just highlighting that a change in command set may need modification on the host side too to adapt to the change
     
  12. Dina Jacobson

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    the single axis commands work thru openbuilds after I recompiled and flashed with $HX $HY & $HZ,
    but not when I send thru VISA. There is an arduino VI I can try
     
    Peter Van Der Walt likes this.
  13. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    Try $HX\n (explicitly add the newline character - however it should be done in labview - CONTROL adds it for you)
     
  14. Dina Jacobson

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    Single axis homing commands work now in labview, not sure why they didn't at first.
    Question thou, I'm using $3 to switch my homing axii, I want 3 orgins, front left, front right & rear right.
    Is the $3 the best way to do that, or should $23 instead or with $3?
     
  15. Peter Van Der Walt

    Peter Van Der Walt OpenBuilds Team
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    $3 is used to make the machine follow Cartesian Standard
    $23 tells it where the Homing switches are
    Machine Coordinates Zero are ALWAYS at axis maxima (see Frequently Asked Questions · gnea/grbl Wiki) but you can set Work coordinates whereever you want using G10 commands
     

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