Filament non stop extruding - MK3S
Yesterday it started to print with blobs and mess here and there. I figured out that the nozzle kept extruding filament even though it was not moving or supposed to print. Like in between moving to a new position. When heated to melting point, the filament slowly extrudes from the nozzle.
I've cleaned the nozzle, heated it to 285 degrees c (ref Prusa instructions), removed the nozzle and mounting it again (online guide), replacing it with a hardened steel nozzle (0.4) from the default bronze (0.4). I carefully mount the nozzle with a gap to the heat block, tighten it very well toward the heat break or what ever it's called (the heating part in the heat block). I've even loosened up the filament pull system to have a very tight fit. Where it just grabs on to the filament and push it reliably while having a good string of filament extruding. I've also checked that there are no leaks around the nozzle or heat block.
Even with all of this, the filament still keeps poring out, in a slow tempo. Around 5 millimeter in 10 seconds. I can't find any suggestions online or on this forum, after hours of searching. Do you have any suggestion of how to prevent this continuously filament dripping? Picture show around 10 seconds of ide state with 210 degree c temp.
Question
Is this filament specific or with all filaments?
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Chuck H
3D Printer Review Blog
Doesn't look unusual to me. If you keep filament at the desired extrusion temperature, more often than not it will leak, to various degrees based on filament. That's why the Mini now uses startup gcode that cools the nozzle down to 170 degrees for standby. I have applied the same modification to all my Mk3S startup gcode profiles, and it pretty much stops all leaking.
reply
I've tried with a couple of PLA and one PET-G filament for now. The behavior seems to be worst on the PLA, but still present on everything.
It might be normal that there is some continuous extrusion, but it would be a problem overall if it's at this level. Just thinking of fine prints like letters or other details. Just within the half a second it takes to move from an end of a model to the first letter it can take half a second. And in that time it could be a a milimeter or less with goo hanging out. Making the start of the letter bad.
I don't think it's supposed to be this way. Otherwise it would be strange that I have not noticed it in the 10 days I've been printing non stop.
In your first post you said
Around 5 millimeter in 10 seconds
That's 0.25 mm per half second, and that's not counting in retraction on travel moves, which exists to counteract oozing. If it were indeed 1mm per half second as in your second post, that would be a different story, I guess.
Consider nozzle temps and moisture absorption impact on filament
[...] Yesterday it started to print with blobs and mess here and there. I figured out that the nozzle kept extruding filament even though it was not moving or supposed to print. Like in between moving to a new position. When heated to melting point, the filament slowly extrudes from the nozzle.
If you were getting different behavior a few days ago, it's always possible your filament has absorbed some moisture. Try another spool or dry your current spool to check. Absorbing moisture will cause the filament to expand which might explain the extra oozing.
A bit of ooze at printing temperatures is normal. You can often reduce this by reducing that printing temperature. A lot of presets and filament manufacturers specify higher temperatures simply because that's easier for them. Hotter filament temps will tend to work in most printers. That doesn't mean you can't often (and usually) get by with lower temps which will ooze less.
Dealing with ooze is an ongoing challenge, and is the underlying reason so many "anti stringing" measures exist. Retraction, wiping, coasting and a host of other slicer features are all about backing pressure off the nozzle and wiping ooze off before moves that cross perimeters. With a bit of tuning, you can reduce it, but it's hard to 100% eliminate it.
I've cleaned the nozzle, heated it to 285 degrees c (ref Prusa instructions), removed the nozzle and mounting it again (online guide), replacing it with a hardened steel nozzle (0.4) from the default bronze (0.4).
Using a hardened steel nozzle usually requires somewhat hotter nozzle temperatures due to the reduced thermal conductivity of steel compared to brass. If you adjusted your printing temperatures accordingly, be aware that the filament is still melted well above the nozzle. That might account for an increase in oozing.
Uncertain
The speed of unwanted extrusion is a bit variable I think. Not as much as I might indicate in the second post, but probably somewhere between 0.25 to 0.5mm a second. Depending on heat and filament type. But I have not checked the actual extrusion rate enough to know for sure. I just know that it's much more of a problem than it's been the past two weeks since I started using my printer. It's been printing non stop for approximately 10 days with no notisable problems with unvanted extrusion.
Filament and temp considerations
Thanks for the info, Bobstro. As I've just started using the printer and filaments a couple of weeks ago, I did not think the moisture could have a negative effect in such short amount of time. Our humidity is 87% right no, but normally it's a bit lower I think. I'll try to use some new filament just to be sure. Going to make an enclosure with a dehumidifier soon.
I'll also try to lower the temp a bit. Thanks for the suggestions.