Dual Extrusion Missing command

[Zorgonaute84]

The dual extrusion process can't print something well because it's missing a command in the GCode generated by S3D.

To avoid oozing during the print of the first tool, it's recommended to implement in the startupscript the first retraction for changing tool. For example, this is my startup script :

T1 ;switch to the 2nd Extruder
G92 E0 ;zero the extruded length
G1 F200 E13 ;extrude 13mm of feed stock
G92 E0 ;zero the extruded length again
G1 E-15 F3000 ;retraction before toochange

T0
G92 E0 ;zero the extruded length
G1 F200 E13 ;extrude 13mm of feed stock
G92 E0 ;zero the extruded length again

then the print begining, and the first tool which print something is the T0. There is no issue with this tool because S3D generate a retraction and an extrusion to compensate this retraction just before the print.
But the issue appear when it's time for the T1 tool to print something for the first time.

This is a part of the generated GCode from S3D regarding the change between the first layer of the T0 tool and the first layer of the T1 tool :

...
G92 E0
G1 E-15.0000 F3000
; layer 2, Z = 0.2
T1
; prime pillar
G1 X81.968 Y160.384 F12000
G92 E0
G1 X90.568 Y160.384 E0.1078 F1442
...

As you can see, the T0 perform a retraction of 15mm to avoid oozing (like a I add in my startup script for the T1), but the T1 is positing, reset the extruder and start to print without perform a G91 E0 F3000 command. So on my case, the nozzle is empty because I made a retraction, and if I hadn't retract, the noozle could be empty too because it was oozing during the first layer.

Bellow this is the transiltion layer script perform by S3D for all others layers :

G92 E0
G1 E-15.0000 F3000
; layer 74, Z = 3.8
;change tool script
T1
; tool H0.100 W0.400
; inner perimeter
G1 X97.293 Y148.083 F12000
G1 E0.0000 F3000
G92 E0

Here you can see that S3D generated the G1 E0 command to compensate the previous retraction.

[KC_703]

Try a skirt or brim to prime both hotends for the first layer. An ooze shield helps with priming on tool change.

My dual extrusion prints look great.

[Zorgonaute84]

Could you share your profile ?

Thanks

[KC_703]

Sure. Its the stock TAZ5 dual extruder profile with some modified temperatures and cooling for my environment.

When you print brim using "both extruder" the brim alternates adjacent outlines... which primes both hotends.

When watching the preview print, it shows the ooze shield print after each tool change. This primes the new tool before printing the actual layer. The confusing part of watching the ooze shield is the optimization which S3D applies... it utilizes the previous tool after a Z change. So its a
Layer 10:
T1-layer
T0-ooze shield
T0-layer
Layer 11:
T0-layet
T1-ooze shield
T1-layer...