Retraction at start - but never undone

[vogtitec]

Hello,
S3D adds an initial retraction at the start of every gcode, just after the start script lines. A few lines later, thie initial retraction should be undone by unretracting the same amount of mm (according to a previous topic in this forum, https://forum.simplify3d.com/viewtopic. ... n+at+start .
But in my case, this initial retraction is never undone, resulting in "none-extrusion" for the first millimeters of the first layer. A sample gcode part looks this way (the important lines marked with "***":

G28
G92 E0
G1 E-4.5000 F1200 ; <--- ************* RETRACTION AT START
G1 Z0.200 F1002
; process Process1
; layer 1, Z = 0.200
T2
; tool H0.200 W0.400
; inner perimeter
G1 X90.600 Y90.600 F4800
G1 E0.0000 F360 ; <--- ************* UNRETRACT 0 mm ?????
G92 E0
G1 X109.400 Y90.600 E0.5628 F1350
G1 X109.400 Y109.400 E1.1255
G1 X90.600 Y109.400 E1.6883
G1 X90.600 Y90.600 E2.2510
; outer perimeter
G1 X90.200 Y90.200 F4800

I tried this with different printer profiles, each time with the same result... S3d version is 4.0.1

Can anyone help?

[rrdavis]

4.0.1 works fine for me. If it disable retractions there aren't any in the file.

Maybe you should post your factory file if you're still having trouble.

[h3ct0r]

Hi,

I'm having this problem too. The first layer is having under extrusion problems due to the retraction before the first layer begin.
Gcode example:

G1 Z0.2 F1000 ; move down to begin wipe
G1 X110 E6.0 F10000 ; wipe print head (extrude material while we do this)
G92 E0.0 ; reset e count <---- END MY GCODE START SCRIPT
G92 E0
G1 E-5.0000 F1500 <------ EXTRA RETRACTION AT THE FIRST LAYER?
G1 Z0.150 F1020
; process Process1
; layer 1, Z = 0.150
T0
; tool H0.150 W0.504
; skirt
G1 X75.029 Y81.763 F7800
G1 E0.0000 F450 <------ NO EXTRUSSION HERE??
G92 E0

[rrdavis]

The line "G1 E0.0000 Fxxx" already primes the nozzle to make up for the retraction you highlighted. It is using absolute extrusion distances, so moving from E -5 to E 0 will prime 5mm.

If you want more info about this, I recommend reading this nice guide on the S3D site:
https://www.simplify3d.com/support/arti ... -tutorial/

[h3ct0r]

Hi @rrdavis,

I still think it is a bug. I don't know how that G1 command correctly prime the nose if no extrusion if being performed (E 0.0000)?
If I change the parameter "Relative extrusion distances" to True (at the fff profile I posted earlier), the GCODE now shows a correct G1 extrusion command and therefore, a good first layer.

Example:
With relative extrusion distances to true:

; process Process2
; layer 1, Z = 0.450
T0
; tool H0.450 W0.504
; skirt
G1 X42.004 Y72.709 F7800
G1 E4.0000 F510

With relative extrusion distances to false:

; process Process2
; layer 1, Z = 0.450
T0
; tool H0.450 W0.504
; skirt
G1 X42.004 Y72.709 F7800
G1 E0.0000 F510
G92 E0

Is this the expected result?

[rrdavis]

Yes, that looks absolutely correct to me. Read the link I already posted. It explains plenty about the E-values and how to decipher these commands.