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Dual extrusion parameters not being utilized


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Posted · Dual extrusion parameters not being utilized

 I'm experimenting with the dual extruders on my Creality CR-X, and trying to create an efficient process for switching filaments using a prime chute.  I've read that I need to zero the "Dual Extrusion" parameters for Retraction Distance and Extra Prime Amount so they don't interfere with my settings.  

 

However, I don't see where these settings are doing anything at all.  I put in fake values (e.g. 12.345) for the parameters and searched for them in the resulting g-code, and they aren't there. 

 

Is this a bug? 

I want to re-use these parameters to reference in my macros (e.g. add "G0 F300 E{switch_extruder_extra_prime_amount}" to the "Start" macro for each extruder), so I can control the amount it extrudes to purge the old color without having to modify the gcode macros.  However, that's a big kludgy and if this someday gets "fixed", would it break my macros? 
 

Or do these parameters only get used when there are two physical nozzles? 

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    Posted (edited) · Dual extrusion parameters not being utilized

    I can configure my Ender for 2 extruders.  With the code in the Extruder Start Gcode I get:

    T0
    G92 E0
    ;GV
    G1 F300 E44
    ;GV

    when switching to T0 and then

    T1
    G92 E0
    ;TTT1
    G1 F300 E10
    ;TTT1

    When switching to T1.

    Those are the way I entered them using the keyword and that's how they appear.

    There must be a tool change for the Extruder StartUp to be included.

     

    What exactly are you trying to do?  Is this part of a "Filament Change" or "Pause at Height"?

    Edited by GregValiant
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    Posted · Dual extrusion parameters not being utilized
    2 hours ago, GregValiant said:

    What exactly are you trying to do?  Is this part of a "Filament Change" or "Pause at Height"?

    Filament change.  Cura inserts the "Start" macro, then the "Extruder Start", then "Extruder End"+"Extruder Start" for each transition, and then a final "End" macro.  In the "Extruder End", I retract the current filament (by "MinRetractForChange"), move to the purge chute, switch extruders, and extrude the new filament (by the same "MinRetractForChange" value).  Then back in "Extruder Start", I extrude "PurgeAmount" - about 30mm - of the new filament to clear out the old color.   

     

    Problem is, if Cura retracts by "Retraction Distance" before my macro is run, or adds its "Extra Prime Amount" after it has already done the "Prime" purge within my "Extruder Start" macro, and does it when the print nozzle is no longer over the purge chute, that would be bad.  

     

    I've read that you should always zero these values to prevent this problem, but as far as I can tell, they're not doing anything at all.  Unless there's something that controls whether they are used during extruder changes (like whether or not the printer actually has two nozzles?), then this might be a bug, and if so, then when it gets fixed, it will screw me up again. 

     

    So I'm wondering how this is supposed to work. Is this a bug or are these parameters ignored because I don't have two different print nozzles? 

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    Posted · Dual extrusion parameters not being utilized

    If the printer has a mixing hot end with "shared heater" and "shared nozzle" then yes, some things are handled differently.  Mostly it's the temperature, but retraction code can be affected as well.

    What firmware is the printer running? 

     

    With the prime tower enabled it looks like the extra-prime is occurring over the prime tower.

    I had the extra prime set to 9.62mm³ which equates to about 4mm of 1.75 filament.  This is the bare Cura configuration with no Extruder Start gcode:

    T1
    G92 E0
    G1 F1200 E9 >>>> (nozzle switch is 16 and retraction dist is 7 so this is the initial prime.
    G1 F600 Z2.4
    ;MESH:NONMESH
    G0 F7200 X217.824 Y210.812
    G0 X215.885 Y211.017
    ;TYPE:PRIME-TOWER
    G1 F2100 E19.99953 ; This is the original 9 + retraction dist of 7 = 16 then add extra prime of 4mm

     

    That looks good to me.  You want to have the extra prime on every tool change and both extruders?

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    Posted · Dual extrusion parameters not being utilized

    OK, figured this out.  I wasn't looking closely at the extrusion distances, which are in "absolute" rather than "relative" units. That was hiding the extra retract and extend distances as changes to already fairly large numbers.  So I do have to zero them in the parameters, and not try to use those values as variables in my GCode macros. 

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