Extra Retraction at Start

[KronosMT 0]

@GregValiant 

G92 E0 ;Reset Extruder
G1 Z2.0 F3000 ;Move Z Axis up
G92 E0
G92 E0
G1 F1800 E-5           <----Here.
;LAYER_COUNT:171
;LAYER:0
M107
G1 F300 Z0.4  <---- picks up nozzle?

 

In the previous code snippets, it is there too.  The amount varies I think based on the retraction settings you have stored.

 

Update:  So I made a noob mistake (yes, I've only had the printer a short while).  It was the z-offset that was really causing the problem for my first layer.  However, the above extrusion is still interesting, although not critical anymore.

Edited January 11, 2021 by KronosMT

[3llled 0]

i am also trying to remove/modify the retract line right before starting the first line being printed.

 

G92 E0 ;Reset Extruder
G1 Z2.0 F3000 ;Move Z Axis up
G92 E0
G92 E0
G1 F1800 E-5           <----Here.
;LAYER_COUNT:171
;LAYER:0

 

i have an ender 3 v2 and cannot pick 2 extruders from the drop down in machine settings, as others say.

 

has anyone been able to either modify the json file or find a way to edit the applicable cura nozzle settings in a backdoor manner?

 

search and replace is not a good option, as i modify the retraction and feed rate frequently depending on what im printing...

 

thanks for any help!!

[Marky 0]

I'm also having the same issue as everyone else. Extra retraction and E0 command between Start code and print code. It seams to be related to the retraction settings in the profile menu! With retraction enabled it's automatically adding the extra code with the retraction amount matching what ever youv'e set in the profile. Doesn't matter what printer you have as I've loaded several with there default settings in tact and its always the same in the code and writes this extra line that matches those settings. It's a real pain as it means the print doesn't start till that retraction is made up via normal print extraction distance, it then dribbles out and F£$s up the print. Below is a code example same as everyone else's. ATM I'm just deleting this line of code manually from the file in a text editor (notebook!) but that's a bit of a pain!

So any other suggestions people?

 

G1 X30 E15.4704 F1200 ;continue purge lines back to start
G1 Z-0.1 X150 F5000 ;wipe nozzle
G92 E0 ;Zero extruder
G92 E0
G92 E0
G1 F4200 E-6.5 =======These are the extra line of code!
;LAYER_COUNT:33
;LAYER:0
M107
G0 F2880 X92.552 Y96.245 Z0.32 ;adjusted by z offset
G92 Z0.3 ;consider this the original z before offset
;TYPE:SKIRT
G1 F4200 E0 Here it zero's the extruder but the fillament is still 6.5 mm up the tube!!!!!!!!
G1 F1200 X92.998 Y95.921 E0.0275
G1 X93.486 Y95.666 E0.05497

[GregValiant 1,262]

I agree this delays the start of any extrusion at the beginning of a print.  I don't like it.  Most people don't notice it as it only affects the skirt or brim.  The "Start G-code" of some printers includes thick and heavy purge lines that mitigate this.

 

@Marky, the final line you have highlighted is a G1 line, not a G92 line.  It advances the filament from -6.5 to 0 at 4200mm/min.  So the filament does indeed end up at the nozzle.  I believe the initial under-extrusion is due to oozing rather than the numbers in the Gcode and although it looks like it should work (the numbers do add up), there is no pressure at the nozzle and so extrusion doesn't start immediately.  In my case that is for anywhere from 30 to 120mm.  For parts with a maximum build plate footprint (that I can't use a skirt/brim on) this delays the extrusion of the first layer of the actual part.  It also can end up with the nozzle dragging around a "string of beads" that ends up in the area of the print.

 

The Search and Replace workaround (that I described earlier) works.  In Marky's example it would SET the extruder to -6.5 with the filament still at the nozzle ready to extrude.  When the later G1 F4200 E0 line advances the filament - there is a serious prime which will sometimes leave a blob.  If I could measure the amount of oozing (which ain't happenin' because it's temperature and time dependent) that blob could be adjusted to nothing and extrusion would start as we expect.

 

One fix for this would require the addition of a setting to the Travel section.  "Initial Print Prime" (new keyword {retraction_print_prime}??) that would effect that single line in the Gcode.  Instead of "G1 F{retraction_retract_speed} E-{retraction_amount}" it would be "G92 E-{retraction_print_prime}.  That would leave the filament at the nozzle, but set the extruder location back.  A few lines later the filament advances to 0 as it does now, but the filament starts at the nozzle, not retracted, so it results in immediate extrusion start which is what we want.

 

A second fix is to add "purge lines" to the Start G-Code of your printer.  MaxX size prints require a snatch-and-grab to get rid of the purge lines before they become part of the print but that doesn't happen often.

Edited February 24, 2021 by GregValiant

[goldjunge491 0]

hi guys anyone get a solution ? 

i get this problem with marlin as well with reprap flavour so its definitly a cura issue -.-

the redline is end of my start gcode G92 E0.0 

and cura add 2xg92 e0 and g1 e-7 

i add  cura project

AI3MSPRO_30_retraction_test.3mf

[GregValiant 1,262]

@goldjunge491This is the gcode I get from that retraction tower.  We are just tracking the E location here relative to the nozzle.

 

G1 E-3 F500 _____________________  -3
G92 E0.0

---------End of startup gcode
G92 E0
G92 E0
G1 F2400 E-7_____________________-10
;LAYER:0
;TYPE:SKIRT
G1 F2400 E0______________________-3

That last E move from -7 to 0 does not account for the last retraction of your StartUp gcode.  The result is that the filament is still 3mm behind the nozzle.  At a line width of 0.4 and a layer height of 0.2 that is 90mm of extrusion that will be missing at the start of the skirt. 

My fix was to always use the Search and Replace plugin.  Using your retraction speed and retraction distance:

Search  : G1 F2400 E-7

Replace: G92 E-3.5

Instead of the filament being 10mm behind the nozzle it is only three.  The prime to E0 then advances the filament 3.5mm which should start the skirt with possibly a tiny blob.  This has worked quite well for me.

One downside is that if you change your retraction distance or retraction speed the "Search" line doesn't work and you would be back where you are until you remember to change the Search and Replace "search" string to match your Cura settings again.  I have installed additional Ender 3 Pro's in Cura because I use different retract distances for different materials.  That means different StartUp Gcodes and different settings for the Search and Replace.  Cura connects the active post-processors to the print and so everything works well for me.

A second downside is that using that search and replace string in tandem with "Relative Extrusion" absolutely will not work.  Every retraction in the file would get changed to a G92 line and the print would really suffer.

[adetogni 0]

This is still valid in 2023. Cura still adds this retraction just after the purge line. If you have a brim you won't notice but if you print directly the piece, you will see a missing part. Is it a bug?

Edited March 24, 2023 by adetogni

[GregValiant 1,262]

It's intentional so not a bug.  I use Search and Replace to get rid of it.  That works unless you are using "Relative Extrusion" (in which case it wipes out all retractions in the file).

Search:  G1 F(.*) E-(.*)

Replace:  G92 E-3

Use Regular Expressions = Checked

(Note the minus sign after the E in the search pattern.)

After some experimenting, I found that setting the E to -3 gives me good starts on either a skirt or the part itself.  Yours may be different.

Edited March 25, 2023 by GregValiant