G-code trouble, filament completely retracts

[jay_s_uk]

@westech move the G91 until after the E moves

[oliof]

@westech start the Z move comment with E so object height is properly calculated.

[MJLew]

Is Cura using absolute extrusion values? If so then the retract code will unload the filament by unwinding the extruder all the way back to -2. My guess is that putting in an M83 (extuder to relative) immediately after the G91 and G90 lines will fix your problem.

[westech]

@MJLew Thanks, I remember this being solved a long time ago. Your suggestion is familiar. I just thought I might look at old non retracting gcode I've printed.

[Bridge Of Don]

@MJLew

We are using 'AstroPrint' as a method of slicing and it appears to use 'CURA', this is for a TRON XY printer

initial section is this . . . . .

;FLAVOR:Marlin
;TIME:6666
;Filament used: 0m
;Layer height: 0.1

;Generated with Cura_SteamEngine master
M140 S60
M105
M190 S60
M104 S210
M105
M109 S210
M82 ;absolute extrusion mode NB NO M83 code anywhere in the code
; Start G-code
G28 ; Home all axes
G92 E0 ; Reset Extruder

At the end of the print the filament would appear to only need to reverse by five mm BUTdrive keeps running for quite some time and the drive wheel spits the filament out , so about 50mm and some.....

I've marked the last two moves of filament in bold

Note that I added the semi-colon before the G4 WAIT command to try and avoid any issues but still it pauses whilst reversing the extruder(and melts the object) before moving extruder away (actually 255 towards back of bed)

What am I missing??

M204 S500
M205 X20 Y20
G1 F1800 X104.431 Y127.059 E1285.40183
G1 X105.005 Y124.804 E1285.44449
G1 X105.999 Y122.97 E1285.48273
G1 X107.346 Y121.488 E1285.51944
G1 X107.979 Y120.99 E1285.5342
M204 S5000
M205 X30 Y30
G0 F7200 X108.124 Y121.135
;TIME_ELAPSED:2422.346628
G1 F2400 E1280.5342
M140 S0
M204 S4000
M205 X20 Y20
M107
; End G-code
;G4 ; Wait
M220 S100 ; Reset Speed factor override percentage to default (100%)
M221 S100 ; Reset Extrude factor override percentage to default (100%)
G91 ; Set coordinates to relative
G1 F1800 E-3 ; Retract filament 3 mm to prevent oozing
G1 F3000 Z20 ; Move Z Axis up 20 mm to allow filament ooze freely
G90 ; Set coordinates to absolute
G1 X0 Y255.0 F1000 ; Move Heat Bed to the front for easy print removal
M84 ; Disable stepper motors
; End of GCode
M82 ;absolute extrusion mode
M104 S0
;End of Gcode

[Phaedrux]

@Bridge-Of-Don Absolute extrusion mode means that the amount extruded is a running tally. If you tell the extruder to do -5mm you're not retracting by 5mm, you're actually telling it to move to position -5 which would mean retracting all of the filament distance that has been used over the entire print and then another 5mm.

Absolute extrusion mode is not recommended and hasn't been for ages. Look into how you can set astroprint to use relative extrusion mode instead. In relative extrusion mode G1 E-3 means to retract only 3mm.

[Bridge Of Don]

@Bridge-Of-Don said in G-code trouble, filament completely retracts:

G1 X107.346 Y121.488 E1285.51944
G1 X107.979 Y120.99 E1285.5342
M204 S5000
M205 X30 Y30
G0 F7200 X108.124 Y121.135
;TIME_ELAPSED:2422.346628
G1 F2400 E1280.5342
M140 S0

Apologies , it doesn't do retract five mm just that the E value decreases by five mm so I assumed that would pull it back by five mm, not sure why it then does another 3mm at the end of print/move away? ? ??

but yes i'll dig into how to adjust this to 'relative' rather than me manually re-doing the G Code

[dc42]

@Bridge-Of-Don said in G-code trouble, filament completely retracts:

We are using 'AstroPrint' as a method of slicing and it appears to use 'CURA

It's a feature of Cura that even if you set it to use relative extrusion, it switches back to absolute extrusion before running code that you supplied in the slicer configuration. So, unless this has been changed, you will need to include M83 in your slicer end gcode.

[Bridge Of Don]

@dc42
Yes now in the clear light of day I see the issue, the commented text from the slicing programme is wrong (in italics)

it is exactly the same issue as the initial post had , sorry to waste folk's time

; End G-code
G4 ; Wait
M220 S100 ; Reset Speed factor override percentage to default (100%)
M221 S100 ; Reset Extrude factor override percentage to default (100%)
G91 ; Set coordinates to relative,

just realised that this (G91) does not affect/alter the extruder/filament setting!!

This line below is the problem as crucially as the E values are still in absolute
G1 F1800 E-3 ; Retract filament 3 mm to prevent oozing

In reality for this item it means pull the filament back to -3mm and as Extruder is still in 'absolute' it will try and rewind about four feet!!

I dont think I need to set to relative as it has already pulled five mm back, but will not to much harm to add a line of code.

G1 F3000 Z20 ; Move Z Axis up 20 mm to allow filament ooze freely
G90 ; Set coordinates to absolute

Not sure how I go about flagging this as an error within the slicing programme?

[Bridge Of Don]

@dc42 said in G-code trouble, filament completely retracts:

@Bridge-Of-Don said in G-code trouble, filament completely retracts:

We are using 'AstroPrint' as a method of slicing and it appears to use 'CURA

It's a feature of Cura that even if you set it to use relative extrusion, it switches back to absolute extrusion before running code that you supplied in the slicer configuration. So, unless this has been changed, you will need to include M83 in your slicer end gcode.

Been away for a short while and nobody else seems willing, but I found that there is an option to set the 'Start' & 'End' code within AstroPrint (and I guess CURA?) so it will always use those bespoke settings for our printer.

This seems to have cured the issue as simply added the M83 command , and whilst there tidied/edited a few of the deafult settings to make for a cleaner start and stop.

Our bespoke ending code now looks like this
G4 ; Wait
M220 S100 ; Reset Speed factor override percentage to default (100%)
M221 S100 ; Reset Extrude factor override percentage to default (100%)
G91 ; Set coordinates to relative
M83 ; RELATIVE extrusion mode
G1 F1800 E-3 ; Retract filament 3 mm to prevent oozing
G1 F3000 Z20 ; Move Z Axis up 20 mm to allow filament ooze freely
(although this still gets a string, which we can live with)
G90 ; Set coordinates to absolute
G1 X0 Y280 F1000 ; Move extruder to the back for easy print removal
M84 ; Disable stepper motors
; End of GCode
M82 ;absolute extrusion mode
M104 S0
;End of Gcode