RE: I need your help! - Tricky printing problem
Check your extruder grub screw, check if gears are loose.
Open door of extruder, remove filament, move extruder til you see the grub screw, check if it is loose, and check if filament path is straight.
RE: I need your help! - Tricky printing problem
To get good prints this is needed:
1. Clean bed, dish soap is the best, and yes if all works you can use alcohol a few times.
2. First layer calibration, needs to be 100%.
Both settings are needed to get good sticking, and to prevent a big ball of filament sticking to nozzle, or a big plate of spaghetti.
Search you tube for first layer calibration, to see examples.
Settings of printer, use 7x7 calibration.
Check with a metal ruler if bed is flat.
If you not sure/confused about first layer calibration, this what I do:
First do a z-calibration.
Print a few cubes spread over the bed, start your first layer to high(a lot), then start going down, then you see the best setting.
Then print over the whole bed with this setting to see if bed is flat.
Powder coated bed do not use it pla, does not work.
Use pei sheet for pla.
Pei sheet and petg, you need to use glue stick or spray window cleaner on bed, otherwise the pei sheet will get damaged.
If you use a filament you do not know, with sheet to use, search for this.
RE: I need your help! - Tricky printing problem
Thanks for the update. Doesn't look like a clog to me, but I also don't quite see what would cause those blobs. You've replaced the hotend so it doesn't seem to be related to oozing from a misassembled heatbreak.
I must admit that at this point I'm running out of ideas and don't have any good suggestions.
I'd get on the chat with Prusa (on shop.prusa3d.com) and see what they're saying.