If you’ve ever tried to print with PETG filament, you’ve probably had a similarly (miserable) experience.
PETG is great because it’s safe to use with food (though I wouldn’t) and is more durable than PLA. It’s a nice compromise between PLA and ABS or nylon.
Anyways, after months of struggling with stringy prints and bed adhesion issues with PETG filament, here’s what seems to work well for me.
Make sure your bed is trammed/levelled/configured correctly
Should go without saying.
Turn the bed heat up! (70C+)
I run mine at 80C but for small items in the center you might get away with 70C. PETG is often marketed as not needing a heated bed, but it sure seems to help. I’m printing on bare glass.
Turn the nozzle heat up! (220C+)
Get that PETG flowing, but backoff if it starts dripping.
Properly set your z offset (I add .125-.150 mm to a paper-levelled bed)
This is key to avoiding string. PETG gets stringy when the nozzle picks up filament as it prints. This can be due to over-extrusion, but it’s usually due to the z-offset not being high enough. I set this directly on my CR-10S by double-tapping the knob and turning the babystep up to 0.125-0.150. I watch the print as it prints the skirt. If your nozzle is still collecting filament, add more babystep. If you’re losing bed adhesion, turn it back down.
Turn down the print speed and jerk!!! (45mm/s print, 9mms/s jerk)
It’s worth a bit more time, do it! I don’t set print speed over 45mm/s, and I turn the jerk down between 9 and 12mms/s.
Turn down the extrusion multiplier/flow rate (I’m running ~94%)
This can help avoid string as mentioned earlier. PETG doesn’t smash down like PLA.