Werid leveling resaults after PETG printing; Why?

[theo_dor]

Hello, Im using an ender 3 pro.

Usually I print with PLA and PLA+, however yesterday I was printing with PETG (and probably did not do a good enough job leveling the printer beforehand). I printed a calibration X and wasn’t paying as much attention as I should, that resulted in the PETG being stuck a few places. I tried as good as I could to peal it off and cleaned the bed with isopropanol.

Flash forward to today: I've switched back to normal PLA and was leveling the bed more thoroughly this time. However, I met a problem that i haven’t encountered before. And the calibration X looks like this:

This is todays calibration X:
1. https://gyazo.com/b2827fc73f776ba69a262133b1f3831b
2. https://gyazo.com/30a70c64a351a56abb155a647656effb
3. https://gyazo.com/2130d44d2e59d35258a4601ec5d9eb2e
4. https://gyazo.com/90f32f047447dbba7ef3cc9fc447d80f

This is after I pealed it of:
1. https://gyazo.com/5e9803a54df07b6f66497eaa33465240

I was not able to level it better and this is the best result. I can’t see or feel any "bumps" on the bed, but I fear that the PETG print might have "raised" the printbed a few places. Could this have happened?

Some spots on the calibration X only got a thin red line (some of them you can almost not see at all). A few seconds after the printer was trying to print at these places the feeder was making a "knocking" sound. I tried to feel the filament and noticed that every time this knocking sound is coming the filament is not going in but jumping a little bit out of the printer. This also makes logically sense since the printer do not seem to print a clear line on the spots where it was when the knocking started. Is this normal?

I know I probably should invest in a glass bed. But is this more hassle? Do I have to use glue every time I print? And is there not a bigger chance of making "cracks" in the glass every time I tried to peel off something?


I also have to say that I am relativly new to 3D printing. Hope some of you guys know anything about this problem and can give me some tips on using a glass bed. I would really appreciate it!