Create Macro with an extrusion rate below 1mm/s?



  • Hello, I have a custom built clay printer which uses mixing firmware as a means of facilitating extrusion through a synchronized syringe and auger extruder. I've been getting great results (thanks Duet Forum!) but have an issue with some macros I'm trying to use.

    Here's the issue: I have a mixing extruder in which one motor spins many many more steps than the other. When I use the control panel extrusion commands or when I write a macro to do some "mix" extrusion to load the printer, even the slowest feedrate causes the faster spinning motor to stall/buzz/not rotate. I noticed that even if I set a feedrate of, say, 0.5 - in the web interface the "requested speed" still comes up as 1mm/s.

    When I'm printing everything works fine, this problem is specific to macros and extrusion from the control panel. Is there a way to write a macro that will allow me to use a feedrate below 1mm/s to allow a proper mixing extrusion to occur?



  • M203 I parameter allows you to set a global minimum speed.

    Usually, when printing, the E axis is allowed to move slower than the minimum to sync, but not when commanded other than in a print gcode stream.

    [edit: The E axis is allowed to move slower than the minimum when its movement is combined with XY movement at the same time, and the speed of the combined movement is above the minimum. see here]

    Set the global minimum to 6 mm/min, which is I think the lowest currently supported. [edit: test this, lower speeds may be possible.]

    https://duet3d.dozuki.com/Wiki/Gcode#Section_M203_Set_maximum_feedrate



  • Many, many thanks @bot this suggestion worked beautifully. This forum amazes me!

    So, ordinarily I don't believe I have a minimum set, and I see that the default is 30mm/s. I don't want to mess with anything other than my macro, so could I use M203 I6 at the start of the macro, and have the macro finish with M203 I30?

    Or should I not worry about setting the global minimum to 6, and just leave it there all the time?

    Thanks so much, this is all incredibly helpful!


  • Moderator

    @tom_lauerman said in Create Macro with an extrusion rate below 1mm/s?:

    so could I use M203 I6 at the start of the macro, and have the macro finish with M203 I30?

    Yes you could.

    @tom_lauerman said in Create Macro with an extrusion rate below 1mm/s?:

    Or should I not worry about setting the global minimum to 6, and just leave it there all the time?

    I can't foresee a case where that would hurt you. I think the lower limit is in place to prevent situations where very low speeds could lead to imperceptible movement, or otherwise appear to be stalled.



  • @Phaedrux Great. I think I will just set the global minimum to 6 all the time.

    Cheers!


  • Moderator

    Yes that probably makes the most sense for your non-standard setup.


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