Is there a cure for embarrassing oozing?

kb58

The post on pressure advance reminded me that I wanted to ask about the possible cause and solution to "oozing." Being very new to 3D printers, I think oozing is a slow flow from the nozzle with no extrusion being commanded.

My situation: When a print is started, the nozzle heats, then the extruder is primed, feeding maybe 25mm of filament. After priming finishes, the extruder retracts about 1mm, but the material slowly keeps oozing. If I can't remove it before the extruder gets to the starting point, a curlicue of filament typically gets run over, adding a few lumps to the first layer.

Is it just a retraction issue? If so, how much is filament typically retracted?

fcwilt

@kb58

Different material behave differently. Some don't like retraction at all.

I just drop the bed, move the nozzle to front-center, prime 30mm, retract (when possible) a small amount, clean the nozzle and bed, then click OK (using M291)

When I click OK the printing usually starts before any oozing.

I also print a brim which allows me to verify that the printing is starting out well. And it gives me a chance to adjust baby-stepping if needs be.

Frederick

jens55

The brim or skirt on a print are there to establish prime and get rid of any oozing.

kb58

@jens55 Sometimes that works and sometimes it doesn't. If the oozed bit breaks off clean onto the bed, no problem. It can be more of a problem if it rolls around and sticks itself to the side of the nozzle cone. Afterwards, during the print, there can be a lump of melted filament right near the nozzle, risking dragging it through the wet extrusion.

I increased retract slightly and watched it. Somewhat surprisingly it made no difference. The nozzle comes to the front of the bed, extrudes XXmm, extruder stops, retracts, and that hanging bit is removed. At that point, it's "Press OK to Start", but then when I look back, there's already maybe 5mm hanging from the nozzle. Wipe that off, go to press OK, look at nozzle, and there's another 4mm. So, I just waited and watched, and over the next minute or so, maybe 50mm of extruded plastic had slowly wormed its way out of the nozzle.
As an experiment, I'll increase retract to something huge, like 5mm, to guarantee that the filament really isn't pushing at all. While I doubt that gravity is enough to allow the molten filament to pass through the nozzle, we'll see. It is a direct drive BondTech LGX, so there should be no Bowden tube antics going on.

fcwilt

@kb58 said in Is there a cure for embarrassing oozing?:

As an experiment, I'll increase retract to something huge, like 5mm

Do that in small increments - some types of filaments don't like large retraction and can jam.

Frederick

jens55

@kb58, what kind of hot end, what filament, what nozzle temp ?

BTW, I agree totally with all your points and have experienced the same.

kb58

@jens55 Sorry, I always forget the context, being too close to the problem and assuming everyone magically knows what I'm using. I'll try better.

Bondtech LGX direct extruder with Mosquito hot end
eSun PLA+ filament
205-215C nozzle temperature

jens55

@kb58, thanks, I would try to bring the nozzle temp down a bit. I use 200C for PLA.

The reason I asked is because some hot ends are known to be oozing more than others.
With my PLA prints I chase the hot end with a pair of tweezers to grab the loose end although a lot of times it falls off while the brim/skirt is being printed. A lot of times I don't even worry about it.
The problem gets worse with a larger nozzle.
One solution that worked pretty good for me at one point was to extrude a bit of material and wipe the nozzle over a scraper on the way to printing.
Also, make sure you don't move s l o w on the way to the print start.

kb58

@jens55 Thanks. Another thing I missed was that it's a 0.4mm nozzle.

Yes, it does move slowly to the start of the print. Speeding it up can help mask the situation, but I was hoping that others have seen this and found a solution.

jens55

@kb58, sorry, gravity is a bitch. There is a solution though ....

https://www.youtube.com/watch?v=ZAPaOevoeX0

fcwilt

@kb58 said in Is there a cure for embarrassing oozing?:

205-215C nozzle temperature

I don't know what PLA+ is or requires but I do plain PLA at 190 - but keep in mind the temp displayed on your printer may not be accurate - so feel free to experiment.

Frederick

kb58

@fcwilt Thanks for the reply. The readings were checked with an accurate thermometer, and the bed and hot end agree within 1.5C of actual temp. I'll try reducing temperature and see how it affects both ooz and overall quality. As you've mentioned, there are so many variables associated with 3D printing, often interrelated, it makes for a long process of sorting them all!

fcwilt

@kb58 said in Is there a cure for embarrassing oozing?:

@fcwilt As you've mentioned, there are so many variables associated with 3D printing, often interrelated, it makes for a long process of sorting them all!

Indeed.

The same can be said of slicers. I normally using Simply3D (S3D) but I have Cura and Prusa which I keep up to date.

I try them every once in a while but their default settings don't work well for me and it's another long process to get to know them as well as I know S3D.

PLA works well for most of what I do.

I have some other kinds of filament I wish to try but I tend to postpone starting down that rabbit hole again.

Try dropping your extruder temp in 5 degree steps. You also up your retraction in 1mm steps.

I prime and clean the nozzle at the start of a print and it gets busy printing the skirt long before any significant oozing occurs.

Frederick