Prusa i3 MK3S 3D printer PETG printing problems



I am using a new Prusa i3 MK3S 3D printer kit. I print lots of things using PLA and PETG.

After a week of great performance I noticed that when printing some objects with PETG filament I often encountered a problem when there's intense stringing, infill gaps, artifacts, the object sometimes detaches from the plate. I use the Prusa Slicer and Cura and print with the temperature 230/90 °C, speed max. 300 %.This problem occurs rather regardless of which infill methods I choose. I see this problem more often when printing models sliced with Cura. Sometimes everything goes fine, but most of the time I need to stop the print due to the model collapsing, detaching from the surface, its parts collapsing due to infill gaps. The printer sometimes makes some 'clicking, cracking' sounds when printing with PETG. My filaments come from Fiberology.

Surprisingly, I have run the selftest, XYZ, Z calibrations and all the other ones without any errors. The wizard told me that the axes are perpendicular and it gave me congratulations. All the other tests went nearly perfect as well.

I do not encounter any problems using PLA, just with PETG. I try to maintain the filament properly (keep it away from moisture, in a closed box). Sometimes (rarely) I get crashes. The filament often builds up on the hotend and I remove it.

I do not know what to do, the build went very well and there are no errors, even though I am a new user and this is my very first 3D printer. I have searched the web and I haven't found people reporting this exact same thing.

Could You help me? What can I do to improve the quality of the prints, perhaps maintain PETG better (maybe I'm doing something wrong) and most importantly, solve the problem?


Posted 2019-06-22T19:50:22.753

Reputation: 495



230 °C is way too cool for PETG and will result in underextrusion unless you print really slow, and poor bonding. Underextrusion in turn leads to stringing because of pressure build-up. I print PETG at 250 °C.


Posted 2019-06-22T19:50:22.753

Reputation: 5 311

Thanks, nice to know. What bed temperature do you use ? The temperatures recommended by Prusa for PET-G are 230/85 *C. – StLuke5 – 2019-06-22T20:53:39.137

1I use 80 for bed. – R.. GitHub STOP HELPING ICE – 2019-06-22T20:55:30.467

1Odd that Prusa would recommend such a low temp. What I don't find odd is that the filament vendors list it as "230-250" or similar - they're incentivized to show a low temperature that you could plausibly print at (at really low speed) because of all the fuss/FUD about PTFE degredation above 250°C. – R.. GitHub STOP HELPING ICE – 2019-06-23T11:39:06.837

1Thanks, this solved my problem. Now I can make complicated, high quality models with PET-G without worrying about any problems. – StLuke5 – 2019-06-25T07:51:39.683


You might try printing with Prusa's recommended settings. They tend to be hotter and slower than I expected.

I have made several pet-G prints with the same machine you have.


Posted 2019-06-22T19:50:22.753

Reputation: 4 180