i've started printing in petg with pla supports since the support surface finish is so good, but whenever i print round things with tree supports i see what looks like layer shifts. since my printer is a corexy toolchanger and not a bedslinger this behaviour has confounded me until today, when i happened to look at the right time. it seems that the layers of the perimeter are not adhering properly, and as the filament cools it contracts, catches on support material, and pulls the entire ring off of the pla supports. meanwhile on the middle part i see no issues at all.
i don't even know what to call this problem. it's not stringing, it's already extruded plastic that does it. layer adhesion issues maybe? the photo up top is a reconstruction of how this print looked on the bed, since it fell apart the moment i flexed the buildplate.
printer settings
printer: Snapmaker u1, 0.4mm hacdened steel nozzles
filament: eSun PETG Basic black, Snapspeed PLA yellow
print settings: snapmaker orca "optimal" preset with some minor changes (0.16mm layer height, 15% grid infill (meant to change that), automatic tree supports on build plate only, 2 layer raft, and support interface ironing enabled)
petg settings: orcaslicer's "generic petg" preset with some minor modifications (12mm² max volumetric speed, 265°C nozzle temperature, 10mm retraction, pressure advance disabsed to use the calibration value from the machine)
here's a look at the underside of the pieces:
and a closeup of the round part:
as far as i can tell, that's pretty much perfect before it falls apart.
i can still print with the "normal" supports because they come up the sides of the circle, but it feels like a waste of filament. any ideas?
I went through the exact problem 2 days ago on my U1.
I was trying to print a very thick cylinder, with pctg directly on the bed (no pla support). Extremely simple and it kept failing. Glue stick and upping the bed temp didn't seem to help. I also slowed acceleration. Oddly fewer wall loops helped so it made me think it was warping. I tried z hop and finally got it printing but it could have been a combo of doing the previous steps too.
It could also be a bed leveling problem. The mesh is only for head 1 and I was printing with head 4. Bed mesh is possible because I first tried printing 4 at once and 1 was good, 2 had a severe layer line but finished, and one failed. I then couldn't re print that last one and kept having the failures where I tried everything above.
that levelling tidbit is interesting. good to know.