odd vertical imperfection - bending outward layer (Prusa CORE One)
Hey everyone. I have a very challenging problem that I've never had before. This design has a middle bottom a few millimeters above the print bed. See the section view of the design (2 versions):
When I print these on the Prusa CORE One, the print has always an odd vertical imperfection that results in a bending outward layer exactly at the height of that middle bottom (see image below):
Print settings on the CORE One:
- PLA - tried various high quality filaments from well-known brands.
- Standard print settings for 0.2 layer (speed and structural)
- Only modification 3 perimeter (does not make a difference in the result if 2 or 3 perimeter)
- Vent grill and door is open
- PrusaSlicer 2.9.3
Despite several year of experience with FDM and various printers, I couldn't figure out the root cause. I've already tried the following with no difference in the results:
- other filaments
- other printer
- different settings like speed, structural
- change the seam position e.g. to rear
- changed the nozzle of the nextruder
My observation and conclusion so far of the root-cause: this odd imperfection seems to be caused by some stress of this middle bottom in conjunction with the infill perimeter. If I remove this bottom completely then the quality is perfect. Or if I would use concentric infill, that has almost no connection between the bottom and the infill structure. But this infill lacks stability of the part. Strange in addition is the fact that the print result is much better on a Prusa i3 MK3S with much less visible outward / imperfect layer at the bottom height.
Any other ideas or recommendations? You may download the 3mf.file here and print with other settings. Very curious if anyone get better results or has ideas on how to improve.