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Cura and dual extruder single nozzle


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Posted · Cura and dual extruder single nozzle

Hey all, i am running Cura as my slicer, i love it, especially since it has support for 2 extruders 1 nozzle/heater.

with the print allowing for a prime tower, and setting retraction when "switching" and also the initial setup of the fillament.

i prefer with both fillaments fully retracted, and it creates gcode for when it needs to push a fillament in and stuf, all works great...
the only thing i am missing, is setting the fillaments back to the original settings at the end.


for my dual extruder, i start out with both fillaments 90mm retracted, wich it handles fine. however, i would like it that when the print is finished, it will pull the active fillament back to 90mm out again, right now it doesn't do that, and i have to send G92 E0 and G0 E-86 (because it pulls the fillament 4 mm out in the end to prevent drip) is there a way to set the slicer to do that? i'd do it with "end" gcode, but it would be way neater if it were possible within the settings

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    Posted · Cura and dual extruder single nozzle

    If the gcode is being produced as you want it with your switch-over retractions correct, prime tower is good, and all that dual extruder stuff then I think you want to put it in your ending gcode.


    G1 F2700 E-86 T{extruder_nr}


    In @ahoeben's list of the Cura keywords "extruder_nr" is defined as "The extruder train used for printing.".  I'm not sure if that would mean the active extruder?  Maybe AHoeben could clarify that.

    You might want that before the M104 S0 line.

    Because Cura doesn't do math in the StartUp or Ending gcodes - if you change your retraction distance you might need to change the E value in that line.

    Most (if not all) gcode prints end with a retraction.  In my case that would be 5.5mm and then there are two 2.0 retractions in the Ending Gcode (prior to the nozzle moving away from the print) so if I put the line in after those retractions I would want the number to be E-80.5.

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    Posted · Cura and dual extruder single nozzle
    4 hours ago, GregValiant said:

    In @ahoeben's list of the Cura keywords "extruder_nr" is defined as "The extruder train used for printing.".  I'm not sure if that would mean the active extruder?

    That list (http://files.fieldofview.com/cura/Replacement_Patterns.html) just shows the descriptions defined in fdmprinter.def.json and fdmextruder.def.json, which are the same descriptions as shown in the tooltips inside Cura. Only the "Application defined pattern" descriptions are my texts. Not all descriptions are great explainations of what each setting does.


    The {extruder_nr} replacement pattern only makes sense in the "Extruder Start G-code" and "Extruder End G-code". Here {extruder_nr} will point to the extruder that is starting resp. ending (ie the extruder mentioned in the tab for the extruder start/end gcode you are editing in the Machine Settings). In the "Start G-code" and "End G-code", {extruder_nr} is undefined (or at best it might return 0).

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    Posted · Cura and dual extruder single nozzle

    interesting! thanks for the replies guys! so the end result is just adding to my printers end gcode.


    G91 ; Set relative
    G1 Z10 E-86 F2400 ; Retract 89mm (and move nozzle up 1 cm)


    as far as i know (by looking at the generated gcode) the slicer doesn't sqitch tools after it finished printing, the extruder being controlled therefore is the primed extruder, no mather wich of the two it ended with. i am going to test it this evening, see what it does 🙂

    one thing i did notice, on the first tool change (first T1) the nozzle doesn't go to the prime tower to prime it, it just starts printing the skirt right away... normally thats no problem, except that i am purging fillament at that point... and so it blobs XD

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    Posted (edited) · Cura and dual extruder single nozzle

    Thanks AHoeben.

    @tomtenberge That will work.  I over-thought it and figured the tool number would have to be called out but that isn't so.  Your code will work on the "active extruder" so whether a print finishes with T0 or T1 it will pull that one back.


    "...and so it blobs XD"  You might be able to take care of that in your StartUp gcode.  If the first Tool Change is called out before the skirt then the purge should occur before the skirt.  There won't be a move to the prime tower but that shouldn't matter if the skirt goes down without the big blob.  It's more experimenting but something like this might work as the last few line in the StartUp:


    G1 X0 Y0 Z15 ;Move to the corner and raise the Z so there is room under the nozzle



    T{initial_extruder_nr} ;End up with the proper tool to start the print.


    I don't know how that would work if you had one of the extruders disabled though (single extruder used for the print).  A two-in-one-out hot end should be OK but there could be a "cold extrusion prevented" warning on a regular dual extruder-dual hot end machine.


    Edited by GregValiant
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