What causes this testpattern error?  

RE: What causes this testpattern error?

Generally either a bed that isnt fully clean or a Z offset that is slightly too low.  Looking at the other lines my bet is on a slightly too low Z.  

The method outlined in this thread https://forum.prusa3d.com/forum/original-prusa-i3-mk3s-mk3-assembly-and-first-prints-troubleshooting/life-adjust-z-my-way/   is far superior to the built in method for adjusting your relative Z offset.

RE: What causes this testpattern error?

Thanks neophyl, I´ll have a look at the other method, tried to locate it yesterday in the forum but couldn´t find it. Thank you for the link!

RE: What causes this testpattern error?

@thomas-m83

Double check that your filament type setting and temperature match what you are printing with. I had strange results similar to this when I loaded some new PETG filament that I actually thought was PLA and thus was printing it too cool.

RE: What causes this testpattern error?

Nah the filament type was right but I played a bit with the temperature settings now, did the first layer calibration like 20 times and come to the conclusion that my filament needs to be dried as well. Currently in the oven, while printing freshly opened ABS, which just prints fine.

RE: What causes this testpattern error?

In your picture it looks to be, to low(first layer calibration), and not sticking enough, bed needs to be very clean.

The 2 things above are very important for your prints, and also so you do not get the big ball of filament sticking to your extruder.

Clean bed with dish soap, then it sticks very good again.

First layer is important, also for sticking.

If still not good, you could also try more heat on extruder, slower first layer, more heat on bed.