Extruder retracts before start of print

Hi All,

My extruder seems to retract about 3-4 mm just before starting to print, this menas that it will only print half of my "purge line"

Could you please tell me what's wrong?

This is my "start" Gcode:

;FLAVOR:Marlin
;TIME:2826
;Filament used: 2.57272m
;Layer height: 0.25
;Generated with Cura_SteamEngine 3.4.1
M190 S60
M104 S210
M109 S210
M82 ;absolute extrusion mode
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G28 ;move X-Y-Z to min endstops
M420 S1 ;Enable Mesh leveling
G92 E0 ; zero the extruded length
G1 X35Y10Z0.2 F5000 ;move out of print volume
G1 X80 E9 F500.0 ;start purge line
G1 X120 E12.5 F500.0 ;finish purge line
G92 E0 ;zero the extruded length

Thanks

Edited 1 time(s). Last edit at 07/21/2018 03:41PM by M1k3.

Do you actually see the extruder motor turning backward (retracting) at the start of the feed line?
I ask because not printing the first part of the purge line is normal. Filament naturally oozes out of the nozzle during preheat, so there won't be any filament coming out at first. The purge line is there to ensure it is properly primed before printing to correct for filament ooze during heatup.

Hi,

Yes, i see the gear of my Titan extruder turning the "wrong" way (i.e. Retracting)

Cant see anything wrong in the start code.
Can you post the beginning part of a actual sliced g-code,upto the 1st layer

Here you go:

;FLAVOR:Marlin
;TIME:7176
;Filament used: 10.6086m
;Layer height: 0.2
;Generated with Cura_SteamEngine 3.4.1
M190 S65
M104 S205
M109 S205
M82 ;absolute extrusion mode
G21 ;metric values
G90 ;absolute positioning
M82 ;set extruder to absolute mode
M107 ;start with the fan off
G28 ;move X-Y-Z to min endstops
M420 S1 ;Enable Mesh leveling
G92 E0 ; zero the extruded length
G1 X35Y10Z0.2 F5000 ;move out of print volume
G1 X80 E9 F500.0 ;start purge line
G1 X120 E12.5 F500.0 ;finish purge line
G92 E0
G1 F3000 E-3
;LAYER_COUNT:121
;LAYER:0
M107
G0 F7200 X67.718 Y55.125 Z0.2
;TYPEKIRT
G1 F3000 E-0.12473

I dont see any retractions commands in your startup code, but noticed these Extrusion commands AFTER the pure lines have printed:

G1 F3000 E-3
;LAYER_COUNT:121
;LAYER:0
M107
G0 F7200 X67.718 Y55.125 Z0.2
;TYPEconfused smileyKIRT
G1 F3000 E-0.12473

See the G1....E are negative on both the first and last gcode commands of your file sample.
So I can see where its probably retracting filament AFTER it has printing the purge lines, but not before.
Being as those commands are generate by the slicer, and not part of your Startup Script, there is probably something set wrong in your slicer - like maybe its set for Relative extrusion mode instead of Absolute....
Hope this helps.