Change Feedrate of currently-running G1?

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  • October 6, 2021 at 12:16 pm #12091
    jimtellier
    Member

    In developing a GUI for controlling a TinyG based CNC router, I have a use-case that I’d like to address, if possible. I have UI controls that allow setting the X,Y,Z axis to a value between 1 and xMAX; these settings are used for all subsequent INTERACTIVE motion (G0,G1) operations. The scenario I’d like to address is:
    User starts, e.g., X-Axis G1 move from X0 to X400, but decides that the previously chosen feedrate is too slow. Is there a way to “modify” the currently-running move operation’s feedrate Without having to do a “Feed Hold” (!) and start anew?
    Ideally, I’d like to provide a “speed control knob” in the UI, for each axis.
    The methodology I’m working toward is to do manual/interactive operations using the UI, and record the resulting gcode for later “playback”/re-use.
    Apologies if this has been answered somewhere before; searched the Wiki but didn’t find anything.
    Thanks for any advice!
    Jim

    October 21, 2021 at 2:23 pm #12092
    cmcgrath5035
    Moderator

    Sorry for delay, the system has stopped sending me messages.
    I have not seen this specific question asked, but will guess that what you seek to do is not easily implemented.
    Have you read any of the Wiki items, such as this one https://github.com/synthetos/TinyG/wiki/Jerk-Controlled-Motion-Explained

    I theory you might write something that broke up the G1 motion into tunable segments, but even that would likely not be effective since the Planner would concatenate the artificial segments and plann them all togeather anyway.

    October 21, 2021 at 3:38 pm #12094
    jimtellier
    Member

    Glad you’re back! 🙂
    That’s a very good article on jerk-controlled motion; that, along with your intuition re: the planner, leads me to think there’s no really good way to accomplish what I describe (at least with TinyG). It almost makes me think that I’d be looking for a feature to simply use “constant acceleration”, with the appropriate commands and settings to control it. Given the advanced nature and advantages of the jerk-controlled motion paradigm, I suppose there wouldn’t be much call for that.
    Thanks for the info! Shout out if you think of any alternatives! 🙂
    Jim

    October 22, 2021 at 1:00 pm #12095
    cmcgrath5035
    Moderator

    If you really want to dig in on this, study G2, the evolution of tinyG into ARM space and much more 3D printer centric. It also has a more robust build system should you want to experiment.

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