I’ve noticed this happening a few times seemingly randomly and I cannot explain it. I’m using just the default monotonic bottom surface pattern.
These lines are on the solid infill for the bottom layers, and watching the printer, what is happening is that it’s overlapping itself by exactly one line when it is doing the infill on parts where it cannot do a single continuous fill across the layer.
In the slicer itself I see no evidence of this instruction, yet watching the printer that is exactly what it is doing.
I have a similar problem on all prints. It’s either weird slicer logic or the printer. My Prusa MK4 from Prusa Slicer prints the same models without this defect.
The worst part about this problem is that these overlaps are not covered even by the last printing layer and they are visible on the surface. It looks like it was printed on a cheap Chinese printer.
This problem in Bambu Studio seems to be caused by the Rectilinear infill in the Internal solid infill pattern parameter. Change it to Monotonic or Monotonic line.
The issue is that Bambuslicer uses Rectilinear solid infill and that chooses the fastest path over the quality of the top surface. Even when flow is perfect, you still see the lines, even the top layer can’t cover it.
Bambu always defaults to speed vs quality and if you don’t know any better, it can throw ppl for a loop.
I see them too. It happens when the extruder stops filling an area, goes and does something else, then comes back and fills in to meet where it left off. Somehow it seems to deposit an extra line of extrusion like maybe its count is off by one. It doesn’t always leave those lines which is why I wonder if somehow it’s adding an extra line that shouldn’t be there. Or maybe it’s just trying to put too much filament into the space left? But seems to be fairly common.
