Linear Advances makes curved surfaces very rough
Hi, I recently activated the Linear Advance feature to improve the print quality on my Anet A8 with direct drive Extruder, Repetier Firmware 1.0.3. I tuned the Linear Advance Factor by printing and evaluating the Marlin K-factor Calibration Pattern. M233 Y110 got me the best results for my PLA filament. As expected, the prints come out more dimensionally accurate, no more blobs on edges and also the layer seam improved quite a bit.
However I just noticed, with LA activated, all curved surface on my prints come out very rough while flat surfaces look normal. The smaller the curvature, the rougher the surface. There's even some amount of overextrusion on rounded edges. It seems like LA causes some kind of noise in the movement of the extruder when printing curves, which manifests itself as a noisy and rough looking surface.
For example when printing a 3DBenchy with LA, the whole rounded surface of the bow looks a bit noisy and the rounded edge at the front of the bow looks really rough. Also the chimney, which is a curved feature, looks rough. When peering from the top over the edges of rounded corners like the ones from the roof, one can notice that the rounded corners stand out a bit, so are slightly overextruded. Another Benchy I printed with LA not activated came out beautifully shiny and glossy surfaces, even on rounded corners, and no overextrusion issues, just as expected.
What is going on here? Is this a bug?