PETG problems after partial MK3 -> MK3S + MMU2S upgrade
Posted this elsewhere, but maybe this is a better place.
I have a pre-built MK3 (Dec) and my MMU finally showed up a few weeks ago.
Prior to starting the upgrade I ran out my first PET-G (Amazon) parts and it worked fine using the Prusament settings.
I rebuilt and reinstalled my extruder with the MK3S parts, but have not yet installed the MMU itself (wanted to get things dialed back in prior to throwing in that particular hand grenade...). I upgraded the printer to the latest 3.7.0 MK3S firmware. I've also been running with the filament sensor off.
After getting my bed leveling dialed in I ran off a bunch of "life Z" tests and XYZ cubes trying to dial in my axis (Y is still off due to bearing play ☹️) in PLA with no issues.
Then I tried to print some PET-G parts and things did not go well. The first few 0.2mm layers (5 I think) of the parts appeared to be fine, but the small support areas (2% of the print maybe) were a mess. Most of the interface layer on the bed stuck, but the structure layers didn't. In some cases it stuck to the interface enough to rip it up, but it looked like most just gunked up on the nozzle. I checked on it after the 2nd layer had started and noticed that the fan hadn't kicked on like I'm used to with PLA (and I don't recall what it did on the pre-rebuild) so I manually turned the fan on to 100%. When I came back I found the mess and stopped the print.
Today I ran another PLA print with no issues, but when I ran another PET-G print (no supports this time) it messed up again. I wasn't as proactive about it and checked on it after about half an hour. 10 of the 12 parts were doing fine, but 1.5 were missing and there was a blob being drug around. I also noticed that the part fan was again not running (4 layers in) and the extruder temp was up at 260 and climbing.
Any ideas why I can't seem to print PET-G now and why the part cooling fan isn't turning on?
RE: PETG problems after partial MK3 -> MK3S + MMU2S upgrade
Petg typically has the fan off, at least for the first few layers, or you will get poor adhesion. PEI isn't the best surface for PETG, but you can help it out with gluestick or (even better) hairspray. If you really like PETG, I like using geckoteck (on my Ultimaker 2, my personal prusa is backordered)
RE: PETG problems after partial MK3 -> MK3S + MMU2S upgrade
I've had similar problems with PETG, and generally it's actually a good thing to have the fan off for this material. I've found that with the fan on the layers do not adhere properly. As long as the fan works for materials like PLA, I wouldn't worry about the fan not working for PETG, as it causes more harm than good. Also, what's your print temp? A higher print temp would cause a gunk up like you described.
RE: PETG problems after partial MK3 -> MK3S + MMU2S upgrade
It started at 230, but on the last print I caught it up at 260 and it was climbing. The print was setup using the Generic PET profile and using Amazon PETG.
RE: PETG problems after partial MK3 -> MK3S + MMU2S upgrade
I've had similar problems with PETG, and generally it's actually a good thing to have the fan off for this material. I've found that with the fan on the layers do not adhere properly. As long as the fan works for materials like PLA, I wouldn't worry about the fan not working for PETG, as it causes more harm than good. Also, what's your print temp? A higher print temp would cause a gunk up like you described.
Thanks for the tips. I'm running a test 20x20x20 cube now and 6mm in it's going well.
I went back to Prusament PETG as my base and found it was starting at 240 and then going to 250, so I turned those both down to 230. I also didn't treat the bed either based on something I saw someone else post about using Amazon PETG.
Hopefully it finishes well and doesn't rip the PEI off 😀