Print reference
Prusa’s Slic3r presets are a great starting point. Here's how I got a few more artifacts out.
Overall settings
| Fill pattern | Honeycomb (Default Cubic) |
| Perimeters | 3 (Default 2) |
| External perimeters | 20mm/s (Default 0) |
| Seam position | Rear (Default Nearest) |
Default (left), my settings (right)
PETG settings
Prusa’s Slic3r settings left some artifacts on parts with broad top surfaces (these were printed in an enclosure; your results may vary). In the end it was too much cooling, contrary to several forum posts’ suggestions.
Turning the part cooling fan off fixed the top surface but gave me a stringing problem. I settled for reducing the fan to around 10%.
Printed with Inland PETG
Printed with the same Inland PETG, spray painted black to show stringing. Model courtesy of Mike-vom-Mars.
Same filament with cooling fan at 10%. Right is spray painted to show stringing, also with 10% fan.
If you have a Prusa i3 MK2S or earlier, it’s important to readjust the first layer height when switching from low temperature filaments (PLA) to higher temperature ones (PETG, ABS, Nylon) or vice versa. The old probes tend to give a different sensing distance depending on temperature, and it might make you wonder why your prints aren’t sticking. Modern probes since the MK2.5 and MK3 release don’t have this problem.
Phantom Jamming
If your filament jams for no reason (i.e. you do a cold pull or poke a needle into the nozzle only to produce no debris), make sure it’s not experiencing heat creep.
After a while of printing with an enclosure I learned that a lot of materials just don’t need the ambient warmth, and the extra heat could raise the temperature of your cold end. I suspect this causes some filaments to get a bit sticky before they’re in the melt zone and grip the inside walls of the extruder just enough to get the motor skipping. Stagnant filament only makes the problem worse because now the filament isn’t leaving with the heat.
TL;DR If you use an enclosure like I do, try printing with the door open.
I’d wrongfully blamed these jams on Prusa’s Linear Advance feature since my problem started appearing around the same time. Sorry, Prusa!