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How to store G54-G59 coordinates on GRBL

Discussion in 'CAM' started by Bjorn Mikkelsen, Aug 6, 2017.

  1. Bjorn Mikkelsen

    Bjorn Mikkelsen Well-Known
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    Hi all

    Im using GRB-Panel/UGCS and xPRO v3 controller with the OX and have limit switches/homing setup.
    I would like to use G54-G59 functions but I cant seem to find out how I store locations in the G54-G59 variables.

    Any help is appreciated.

    /Bjorn
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
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    in GRBL-panel when you click the big '0' buttons to the right of the X Y and Z displays, it sets the active offsets.
    you can see the current status on the 'Offsets' tab.
    g54.png
     
  3. Bjorn Mikkelsen

    Bjorn Mikkelsen Well-Known
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    Hi David,

    Sorry for the long delay answering, summer holiday :)

    Stupid me, never noticed the tab :)
    Anyway it seems to work, only one thing I still havent figured out:
    I start up with doing a homing run, my OX is set to move 2 millimeter away from the homing position.
    So after my homing my coordinates is Z = -2

    When I then run my gcode (generated with fusion 360) one of the lines read :
    G53 G0 Z0
    meaning it goes to Z=0 and since that makes it hit the limit switch I get an error (ofcourse).

    So my question is ? do I need to change that to Z-2 instead or is there anything else that I could do?

    Ohh and another question :) :
    So I do a homing run, then run the gcode with for example G55 that moves the router somewhere on the table.
    Normally I have some hold down clamps sticking out, and when the CNC moves the router to G55 position it doesnt know of the clamps.
    How does people get around that problem? (without a sucktion board)

    Thanks alot for the help.
     
  4. David the swarfer

    David the swarfer OpenBuilds Team
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    There are 2 ways:
    you can edit the .cps post processor file to make that line G53 G0 Z-3 so it always safely goes to the top if Z travel.
    or
    you can set an option in GRBL's 'config.h' that tells it to make the home position 0, not sure how it handles pulloff but it is something to look at , look for HOMING_FORCE_SET_ORIGIN.
    In fusion you set the safe retract height to clear the clamps. If you model the clamps as part of the drawing it should be even more clever about missing them (-:
    You leave the G53 G0Z-3 in place, because that is what is supposed to pull Z up to clear clamps during initial positioning moves.
     
  5. Bjorn Mikkelsen

    Bjorn Mikkelsen Well-Known
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    Great I will try them all, wasnt sure if Fusion would take them into consideration when going from homing to "start position" or just under the milling operation.

    I will let you know what I end up with.
    Thanks ! :)
     

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