How do I prime the nozzle for longer using G-code?

[2go 6]

So, basically, the title. I have a bunch of prints to make that barely fit on a build plate, so printing without a skirt. Right now, I move 10mm-20 mm of filament before every print to prime the nozzle for printing. Can I make Cura do it via start G-code?

 

Right now, Cura shows only one line in the start G-code -- 'G0 F3000 Y50 ;avoid prime blob'. What should I add to make the printer push out 20mm of filament before starting a print? I Googled for a sec, added this line 'G1 E15 F300', but nothing changed. Thank you.

[Slashee_the_Cow 270]

Are you dealing with multiple extruders (which each have their own startup gcode) or just setting the gcode for the printer?

FWIW: G0 F3000 Y50 is just telling it to move print head to move to either 50mm in the Y axis or move 50mm on the Y axis (depending on whether you're using absolute positioning) at 50mm/s, and the comment makes me think it's there to avoid a prime tower in case one is there.

G1 E15 F300 will just make it spew out 15mm of filament wherever it currently happens to be - which could be very bad if it's at (or near) bed level, it won't actually print any lines to get any crap into the system onto the bed, just pee out filament.

 

If you're just dealing with the printer gcode, it sounds like you want a nose wipe - where prints a line or two on the very edge of the bed before it starts. The code for that is something like this:

G92 E0 ; Reset extruder position
G0 X0 Y0 Z0.28 ; Go to start position
G1 X0 Y145 Z0.28 F1500 E15 ; Print first line
G0 X0.4 Y145.0 Z0.28 F3000 ; Move a little to the side
G1 X0.4 Y20 Z0.28 F1500 E30 ; Draw a line back
G92 E0 ; Reset extruder position

That's just for my printer - it may be different depending on your printer. (Things like whether origin is at centre - mine isn't - and whether you're using absolute positioning - I am)

Edited December 11, 2023 by Slashee_the_Cow

[2go 6]

Apologies, I could have explained what I'm attempting to do more clearly. I have a fleet of old Ultimaker 2+ printers and currently use the latest version of Cura.

 

When I start the print, the printer heats the nozzle in the bottom left corner and extrudes a small amount of filament into the air before printing the skirt. I wish to adjust it to extrude a larger amount of filament in the air, perhaps for an additional five seconds, so that it deposits a poop-shaped pile of filament in that corner.

 

Simplify3D does this, but I'm unsure how to replicate it in Cura.

[Slashee_the_Cow 270]

Is there already a G1 command with a positive E parameter anywhere (probably near the end) in the start code already? Something like G1 F200 E15, except those F and E values are just placeholders. If there is, just increase the E value by the appropriate amount (like if it's already releasing filament for five seconds, double it). The F value controls speed, and E controls distance, so if you double the distance at the same speed, it'll sit there spewing filament for longer.

[2go 6]

There is only one line in the start G-code, default Cura settings (screenshot attached). I suppose I should add G1 command before the already existing single line of G-code?

 

edit: I guess pre-print priming stuff is done by printer firmware, since there's not much going on in start G-code section.

 

Edited December 12, 2023 by 2go

[Slashee_the_Cow 270]

Yeah, Ultimaker + Cura does a lot of the gcode work for you. If you tried adding a G1 E15 F300 (extrude 15mm in 5 seconds, sorta slow but beside the point) and it didn't change anything, then I'm not sure there's anything you can add in Cura that can change it. I'm going to tag out for @gr5 who does know Ultimaker printers and hopefully notices that tag 🙂

[gr5 2,176]

So in the screenshot above you have the gcode flavor set to "ultimaker".  You can change that to "marlin" and then suddenly start and end gcodes should appear that you can edit.

 

The cool thing about UM2 series printers is it stores a bunch of things on the printer (not in cura) including:

bed temp, nozzle temp, retraction distance and speed, filament diameter

 

It's probably rarely used but I have printed the exact same gcode in pla and then petg by just changing the material on the printer.  So it's kind of cool.  But you can disable all this by doing the above change I mentioned and now you can set all these things in cura settings (like temperature) and also now you will see the priming code and such.  And you can edit it.

 

You can also have a mix where some jobs are "ultimaker" mode and some are not.  The printer itself knows the difference by the comments in the header.