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Prusa MK3S+ with Revo - how do I fix PETG blobs and filament sticking to the nozzle? (www.imgur.com)

submitted 9 months ago by EnglishMobster@lemmy.world to c/3dprinting@lemmy.world

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I'm glad this happened on the first layer of a 2-day print, at least.

I'm using Revo's recommended settings for PETG, on a 0.6mm nozzle, printed with Prusament PETG.

I haven't printed anything since July, and this is the second print in a week. The first print was mostly fine, but had some strange artifacts on one end of the print which I attributed to Octoprint acting up (I've since sanded them away so I don't have pictures). Just to be safe, I greased the smooth rods, checked the belt tightness, and re-ran XYZ calibration + first layer calibration.

I watched this whole first layer get put down - everything seemed to be absolutely fine, with a couple "zits" in one section (actually right next to where the blob landed; you can see them in the second picture).

The print head lifted up to start another section of the print and this massive glob of PETG fell off the hotend and landed right on the print, which forced me to cancel. Then I noticed a big ol' glob on the nozzle too (no idea where it came from). Trying to remove it broke the silicone sock.

I've ordered a new nozzle just in case this one is worn, but I'm curious if anyone has any ideas as to what could be the underlying issue here? My retraction length is 1.1mm with a retraction speed of 27 mm/sec.

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[–] beeng@discuss.tchncs.de 2 points 9 months ago* (last edited 9 months ago) (1 children)

Feed rate slightly too high, so that after 5 mins it can build up pressure and once it lifts, it shoots out the pressure that built up.

[–] EnglishMobster@lemmy.world 1 points 9 months ago* (last edited 9 months ago) (1 children)

Interesting - I'm using the stock values for feedrate (max 200 mm/s for XY; 12 for Z; 120 for E; no min feedrate specified), but those are probably tuned for the stock hotend and I can imagine they probably differ for the Revo.

The only thing I can find for the Revo that seems like it would give the numbers I need is this page which talks about max flow rate, but that's different than feed rate (I'd imagine). The linked calculator puts my settings well within standard limits.

I can't seem to find anything else online about it - is it just bringing the XYE values down via trial and error, or is there some formula I can use to calculate the correct feed rate?

[–] beeng@discuss.tchncs.de 1 points 9 months ago

Sounds like you're within limits, I would just try a few steps less for this particular model and see if it makes it better.

[–] brettvitaz@programming.dev 2 points 9 months ago* (last edited 9 months ago)

dry the filament - most filament is wet even if it is brand new
calibrate flow rate
calibrate first layer (nozzle height)

I rarely deviate from Prusa Slicer’s built in profile for Prusament and have great results. I would try drying the filament first if everything else is working well.

[–] turkalino@lemmy.yachts 1 points 9 months ago

I’d love to know if you find out anything that helps, I have a similar issue with PETG where the nozzle clogs up during 50% of filament changes. I have to completely dismantle the head to clear the blockage. It’s incredibly frustrating

[–] Everto@lemmy.world 1 points 9 months ago (1 children)

I have a MK3S and a MK3S+, one with a stock nozzle and one with a Revo. I print the same gcode on both machines and haven't seen a need to tweak the settings for the Revo. Have you tried slicing with the default settings for Prusament PETG in Prusaslicer?

[–] EnglishMobster@lemmy.world 1 points 9 months ago* (last edited 9 months ago)

Yeah, originally I had kept all the settings stock but I was having issues with bed adhesion and stringing when I swapped to a different PETG brand. I played with my extrusion rate until that other filament (Overture PETG) printed mostly okay... but honestly that filament still gave me issues on the first layer (mostly edge curling on the bed) so I just ate the extra cost and swapped back to Prusament.

I suppose it probably couldn't hurt to try a print with all the stock settings just to rule things out.