PETG balling up on the Nozzle

New to the forum, just got a Anycubic Kobra 2 Pro and mostly has been great but I have a problem where sometimes when I print PETG it will start balling up underneath the printer nozzle and it will leave some parts empty and balls of filament everywhere. The strange part is that some things I print work fine and others won't work. Same settings back to back. I thing smaller prints work better than larger prints but sometimes even the exact same thing will work the second time. If it makes it past the first few layers up from the bottom it will be fine for the rest of the print. Attached is a example of a failed print.

I use Prusa Slicer and have taken the suggested settings and made slight changes to them. I print at 230 DegC (I used a temp tower)

I thought it might be retraction length? (currently 2mm) but on big prints it happens when there is no need for retraction. I have tried different temps and nothing seems to affect this problem. I tried with adaptive fan and also the fan all the way off. I have tried cleaning my nozzle hot and cold.

Scanning the internet and forums I have came to the end of what I can figure out as when I look at the list of settings there are lots that I have no idea if I should change or not. Hopefully someone on here knows what's up or can seer me in the right direction.


Thanks for any help

It's not necessarily THE answer, but ensure that your filament is dry. PETG absorbs moisture and can cause so many unusual problems when printing. The before and after photos on the internet are quite dramatic.

I just put on a brand new spool this time. Do they ever come with too much moisture?

Fresh out of the box a spool of filament can contain excessive moisture, yes.

I'll try to get the moisture out. I don't think this is my problem though because different spools act the same way and also some prints will work and some won't of the same spool.

Might be a partially clogged nozzle, filament snagging somewhere between reel and extruder.

Check for any signs of extruder teeth being clogged and filament grinding, which will leave particles of filament scattered round the extruder gears and possible some falling like fine snow on the buildplate

Filament tangled on the reel and getting trapped under another filament wind.

Yes, that's why I suggested it's not THE answer.

Also try raising temp in 5 degree increments.

It might even just be a bad roll of filament.