Hey everyone, I am trying to get my piece of junk Tiertime UP Mini 2 printer to work somewhat reliably, but it also is my first printer, so I don't have a lot of practice with debugging these things. While flushing some PLA through the Hot End (without a nozzle) I noticed that it looks very bubbly at temperatures between 195°C and 210°C (see picture above) and I wondered if this should tell me that I have been printing too hot. With lower temperature (160°C) the film looks pretty smooth (see second picture below) but that sounds way too low to actually print PLA with. I now tried printing with my 0.4mm nozzle at 190°C, but had no adhesion on the bed. It was no better at 200°C. Both times the bed was at about 55°C. Is there something I do fundamentally wrong or is that a normal texture for PLA after heating? I would have printed a temperature tower, but firstly I have no adhesion on the first layer and secondly I do not think I can set different temperatures for different regions in the Tiertime slicer I have to use with this printer. Usually I would like to try out a bunch of things, but before I sink hours into this and clog my nozzle really badly again, I wondered if any of you has some suggestions.

Context: I am working on this on and off for the last year, but it is quite frustrating, because with each clogging I need so much time to get the nozzle and hot end free again. I got the printer for free and its form factor fits perfectly into one space I have free in my apartment. The printer came loaded with ABS, but I didn't like the smell in combination with air filter, that has never been changed. So I figured PLA would be better for a beginner. Maybe my problems started there, because I didn't consider that cleaning might be necessary for the switch. I was able to get a fine benchy out of there a couple of times but usually after 3 or four prints, I get clogging in the heating element (I suspect heat creep being an issue). So right now I have some flow through the hot end again after I cleaned it over a couple of days with cycles of soaking in acetone and picking out softened PLA. When doing a couple of cold pulls with a cleaning filment by eSun at 110°C, I noticed the behaviour described above. I also exchanged the nozzle once although that one might be messed up now as well. A couple of times the prints failed by not extruding anything anymore and liquid PLA coming out between hot end and nozzle. But last time, I am pretty sure the clog was higher, somewhere inside the hot end, which is why I did this long solvent cleaning.

I am happy about any help and tips you might have!