Banding artefacts before rounded corners

Bambu Lab H2 Series Troubleshooting
1

Hello everybody. Until now everyhting came out just fine from my new H2D. Until I printed this model. I am seeing artefacts shortly before the rounded corners are starting. The pattern seems to repeat itself with a distance of 11mm.

Now the tricky thing I cannot get my head around is if I rotate the object 90 degrees, I do not see these artefacts. Nor on any other prints I have done in the 60hrs.

There is no difference in speed, flow, temperature or fan speed accoding to the Bambu Slicer, also no internal structures at those heights.

Although it seems minor, I am a bit concerned if it is hardware related and whether I should contact support. Is this within the expected margins of the FDM printer.

Things I tried:

  • Different filament (both Bambu PLA)
  • Dryed filament
  • Flow calibration
  • Did the belt tension procedure
  • Cleaned an greased the lead screws just in case
  • Full calibration run

Any advice where to look, and what that could be causing is really appreciated.

PXL_20251216_192836728.MACRO_FOCUS.MP-EDIT
PXL_20251216_192836728.MACRO_FOCUS.MP-EDIT1920×1080 144 KB

PXL_20251216_192747245.MACRO_FOCUS.MP
PXL_20251216_192747245.MACRO_FOCUS.MP1920×1080 94.6 KB

box_sample.3mf (39.3 KB)

2

I wanted to give you a quick update so it is documented:

I contacted support about it. They could reproduce it on their machines. Turns out that this is the arc fitting algorithm overfitting for this model as it was already at a quite high resolution for these corners.

Disabling the arc fitting (or using aranche wall generator) and the print is nice again. And most important for me: it is not a hardware related thing after all.

Bambulab R&D will look into optimizing the arc fitting for these sort of models, at least that is what they replied.