I’m using Cura. If the left extruder starts first → dual printing ok.
But if i need the right extruder to be first - then i have a problem. It doesn’t print skirt after exchanging extruder, so i can’t purge the left extruder before i want to use it
Does anybody have the start/left/right extruder codes to make it work?
Not sure I fully understand your problem.
Here is what I get for a two-extruder print:
The skirt of the red filament is printed first, followed by the first layer of the red object. Then the skirt of yellow filament is printed, followed by the first layer of the yellow object.
Cura 5.7.0
No Prime Tower
please create the object with 2 layers. the first layer assign to the right extruder and the second layer assign to the left extruder, add the skirt and try to print. but set the temperature for the left extruder for the initial layer to zero (as we don’t need to print it at first layer)
and the second version → try to print with left extruder as the first layer and the right extruder with second layer.
then you will understand what i’m talking about
1st version
Left extruder: yellow; T=210°C; T(L0)=0°C; Assigned layer=1
Right extruder: red; T=210°C; T(L0)=210°C; Assigned layer=0
Both skirts are printed on the 1st layer. However T of left extruder is 0 for layer 0 => it will not extrude successfully. To my understanding, Cura will try to print with cold filament… This is the expected behavior and I would’t try that.
2nd version
Just inverted left and right extruders
Looks like expected behavior to me.
Sorry I still didn’t get what is the issue.
To get what is the issue you have to print the models with both methods, not just to slice them 
In Ver2 if you put the Temp of Right extruder to zero, suddenly you will find that you CAN print (with cold Right extruder, coz it will heat up later and will work before the second layer starts)
In Ver1 you HAVE TO HEAT UP BOTH extruders initially and you have no other choice (you CAN’T set the Right extruder to zero).
The other issue is that the skirt for the Left extruder you can’t print with the temp that you assigned as the Material Temp in Cura. It will be printed with the Temp of Right extruder. Also Oops!
And usually i use script before printing 1st layer and i purge the nozzle before printing, so this, again, is also a problem, because starting extruder is ALWAYS Left extruder.
How to avoid this situation i don’t know.
I created some scripts,but generally i can’t print with the right extruder (Ver1) same simple way as Ver2