MakerGear Forum

Question for you G-code guys......I'm trying to eliminate the post-print drip that always forms on the nozzle without people having to remember to wipe it off.....it's a potential scrape issue with the new printer setup - the nozzles on the duals are set at the same height, and PETG is pretty oozy for a while afterwards.

Jin, I saw this in one of your old Wiper scripts....this should handle retraction, right? Or should I just use M102 whatever? Tim? Jim? Ed? Anybody else use one for that?

G92 E0
G1 E-6 F1600
G92 E0

Just want to pull it back up out of the way before shutting it down.

Thanks guys.

I have mine set to retract 5mm on my end script and it still manages to ooze. it means less for me since I only have a single extruder, I dont know what can be done about petg oozing on a dual setup though.

Here's my current finishing g-code, with comments:
I only center the extruder before dropping the bed because my wire management consists of draping loose loops of wires behind and over things, and I don't want it to get wrapped around the z-knob as it spins.

Jules wrote:this should handle retraction, right?

Yup, but the nozzle will still drip.

Normal retraction (of 1 mm or so) depressurizes the hot end and reduces the flow rate enough that the nozzle can get from here to there without dribbling.

That also happens at the end of the print, before your ending G-Code gets control, so the drip you see happens after a normal retraction.

Retracting 6 mm, as in your code, will form an air bubble inside the nozzle, but the hot end walls will still be covered with molten plastic that oozes downward. As the air bubble heats up, it will push plastic out of the nozzle to form a blob. Retracting even more will enlarge the air bubble, with plastic still remaining on the walls. I think you can reduce it, but not eliminate it enough to make a difference.

I've tweaked the startup routine for my (single) M2 to maneuver the (possibly cold) extruder to the front edge of the platform, heat it, then scrape the blob off on the edge of the glass:
http://softsolder.com/2015/03/31/makerg ... -whatever/



As a result, I just wipe carbonized PETG off the sides of the nozzle while it's heating, if there's enough gunk to matter, and don't worry about bumping a cold plastic blob on the glass.

Perhaps you could do something like that with the dual + probe machinery? During the startup routine, move forward to the front edge, heat both extruders, wipe them clean, then proceed with platform probing and suchlike?

Lacking a mechanical valve at the nozzle, there's no way to prevent a hot bucket of goo from leaking through the hole in its bottom... [sigh]

Super! Thank you gentlemen!

(And I realize that was probably too brief an answer, but a gal pal of mine was chewing my ear off on the phone while I was trying to type.....I'll take a closer look and see if there is anything from all of that handy info that I can put to use for the newbies. )

Oh crudsies.....you're all correct....it still oozes a bit.....it's better, but it still comes out some. (Well that's probably the best I'm going to be able to get, and it's probably enough to keep from whacking the print with the inactive nozzle drip. I'll drop in a little "vertical jump on retraction" too, just to be on the safe side.) It's a shame I can't just wipe it while the nozzle's still hot, but i'd knock the print off.

And Ed....that is the most entertaining "comments" selection i've ever read.....having to fight with myself to keep from going in and changing all of mine to ".....and then you trail snot across the plate".

Thanks fellas!

Jules wrote:the most entertaining "comments"

Just tellin' it like it is ... [grin]

If you start to pre heat an m2 that has the retraction of 10 or 20 at print end it usually takes at least ten minutes , but usually more for my setup. At least with my machine if I wipe it after the machine heats it is all good. It has burned out the filament during pre heat.

Well, i finally got it going fairly well, but i had to make a couple of changes to the script...it does work, but it's more wasteful than i like....

That bubble does form in the nozzle after the 10mm ending retraction, causing the PETG to consistently stick at the top when doing the next purge....impossible to scrape off unless you up the purge to 60mm of filament and slow the wipe speed down to F600. So far, in testing, that amount seems to weight it down enough that the larger glob generally falls off to the side before the wipe.

It solves the buildup problem on the inactive nozzle for single filament prints though, which was the initial goal.....nothing ever comes easily does it?

Anyway, thanks again for all the help guys! This will have to do.