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About half the time recently when printing with PLA, I see that holes or loops have a line of filament running approximately through the middle which seems to be one of the inner perimeters having detached and contracted, but is still attached on both sides. Is it a temperature thing, an extrusion thing? I can't find a pattern. Bed adhesion is great. Bambu H2C, mostly printing with Bambu Basic PLA.
That looks like multiboard snaps. They are specifically designed for 3 walls, .2 layer height and .4 nozzle.
I had problems that looked like that from z hop. The nozzle was dragging. Enabling zhop (or increasing it a tiny bit) can stop the print head from dragging and leaving filament wisps.
Those sections of extrusion are being pulled away from the print as the nozzle moves, because for whatever reason they are not adhering to the rest of the print properly.
Increase print temperature, reduce print speed, or reduce travel move speeds.
Also a sanity check, look at your slicer's output preview and ensure nothing about that model is causing it to freak out and attempt to print in midair...
I'd considered raising the temperature a little to get the perimeter to stick better to its neighbor, but I wasn't sure if hotter printing would worsen the thermal contraction, which is what I was originally suspecting was happening. Nothing ever pulls off from an outer perimeter, it's only inner perimeters of empty loops or holes.
Nothing ever pulls off from an outer perimeter, it’s only inner perimeters of empty loops or holes.
Isn't that obvious? Try making a circle of a certain size on a flat, empty table, by dragging a string. The circle will become smaller, than the target size because of the drag.
Now drag the string around a gluestick, it can't be smaller than the gluestick's circle because the gluestick is in the way.
Your nozzle won't travel anywhere outside of your model's outer perimeter because it has no reason to (unless your g-code is super borked, see my comment about your slicer above) but it will be dancing around within the space between the outer perimeter and center of your model many hundreds of times. Any extrusions pulled off on the outer perimeter would stay somewhere within the model.
Try enabling avoiding crossing perimeters in slicer.
Check nozzle cleanliness - remove any junkus from outside.
See if slower print speed helps?
You're sure it's the first layer as well as others? The print bed side looks pretty cleanly pressed against the build plate, it seems unlikely you'd have issues unless there is some major deviations in your bed leveling. It mostly looks like the gcode had it try to print in the air/with nothing for it to stick on.
As others have pointed out this is pretty common for inner circles and you may have to find a way to tweak the print settings or the design to be more printable. You can look through the preview layer by layer and check the tooling path for anything that would obviously not work.
That being said, if you'd like to share the 3mf file I wouldn't mind poking at it later... 3mf is what Bambu slicer uses isn't it?
Is the room temp high enough with no cold drafts? I live in a cold area and have had print problems with the room being to cold.
It's enclosed
it's not being adhesive, trying a 5+ degrees might help. try setting drawing the outside parameters first.
It looks like that's your first layer? Poor bed adhesion coupled with a slight under extrusion might be doing it. You could also try to slow down your first layer dramatically (50% or more slower)
It's both first layers and higher. No pattern I can find. Bed adhesion is definitely fine, I haven't had a single lifted corner since I started using the SuperTac plate.
I would try bumping the flow up manually a bit, and setting it to run slower. Try changing your filament to Generic in the profile too, if it'll let you.
Then see if you get a few clean layers trying all of this.