After having a lot of trouble trying to print with PLA on my Zortrax M200 Plus, I finally discovered what the problem was. The symptoms I had were that my PLA wouldn't print at all at the typical PLA temperatures of up to 210°C, but the printer would make some clicking noise. At higher temperatures the PLA finally came out of the nozzle, but not as much as it should be. The result was very bad rafts, but which due to the high temperature stuck very much to the printed piece and couldn't be removed.

Finally the whole system broke down and wouldn't print at all any more, just making that clicking noise. Cleaning and then changing the nozzle didn't help. Ultimately I had to open the extruder to fix the problem. What turned out was that the Zortrax M200 Plus only has a single roller in its extruder, without a second metal roller to press the filament against while transporting it. The PLA I used had a very smooth surface, and is rather hard. So the roller couldn't grip the filament right and didn't push it properly into the heated channel and the nozzle. The clicking noise the roller slipping of the filament.

The only solution was to go back to ABS, which is softer, and thus the roller gets a better grip on the filament. But I have to say that I am a bit disappointed with the Zortrax extruder: All other 3D printer extruders I have seen up to now are using two metal rollers, and not just one.