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

submitted 1 year ago by EnglishMobster to c/3dprinting

7 comments fedilink hide all child comments

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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[–] [email protected] 2 points 1 year ago* (last edited 1 year 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 1 points 1 year ago* (last edited 1 year 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?

[–] [email protected] 1 points 1 year 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.