Re-establishing Axis positions after RESET

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  • May 10, 2018 at 11:49 am #10977
    jimtellier
    Member

    I’m a bit confused as to the proper approach to getting TinyG to recognize the
    actual current positions of X,Y,Z after I send a ^x (or hit Reset button). Seems
    like Posx,Posy,Posz all come up as “0”, which I suppose is reasonable, but given
    that my software “knows” where everything was when it stopped, isn;t there a way
    to set X,Y,Z actual positions Without going thru a homing cycle?
    My issue with using homing is twofold: it takes unnecessary time, and given that it
    assumes axes are at “0” to start, the POSn results coming back during homing will
    have values that are outside of valid ranges. For example, X-axis was at +600mm
    when Reset occurred; homing X results in a stream of negative position values, which
    isn’t consistent with what shows up in my GUI, of course.
    Am I unaware of a Gcode command or a TinyG parameter to set current positions?
    Thanks for any ideas!

    May 10, 2018 at 3:23 pm #10978
    cmcgrath5035
    Moderator

    A tinyG reset does set the current position to (0,0,0).

    I have never seen anyone try it, but I would think you could use the last position info that your software stored as an offset in the coordinate system your G codes runs in.

    That sort of assumes you also know where in your G code job the reset occurred.

    If you restart in the middle of the Gcode job, be sure to send any state setups that might have been issued, such as inch vs mm.

    Let us know if this works for you

    May 10, 2018 at 4:08 pm #10979
    jimtellier
    Member

    OK, I’ll give it a shot.
    I’m supposing that, for example, I’d use G92 x147 y120 z-53
    upon beginning my “resume” after reset operation, and everything would seem “normal”.
    But what would I expect a homing operation to do? (I mean, after the offset).
    Do you think I’d want to G92.1 after homing finishes?
    I’ll poke at it in a little while and let you know what I see!
    Thanks for the quick reply!
    Jim

    • This reply was modified 6 years, 7 months ago by jimtellier.
    May 10, 2018 at 7:28 pm #10981
    cmcgrath5035
    Moderator

    I read your query to say you did not want to re-home.

    Rehoming would of course be most accurate, but does take time and would still require you to figure out from where to restart your Gcode job.
    And all of this discussion probably dictates that you generate Gcode in absolute mode, rather than relative mode for best results.

    If you were to re-home, then proceed to run absolute mode Gcode, then offsets should not be required.

    What sort of jobs are you running?
    Small errors in a long 2.5D job would probably not be obvious, but restarting a fine pitch PWB milling job may not work so well.

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