I have been doing a lot of experiments lately to come up with an interlocking shape to make a thin-walled round box that would show only side grain but be thick enough not to fall apart, but as thin as possible. with a tight kerf.
So I was very disappointed when the cut (1)was very smokey, the kerf very wide and it would not cut through. So as it was scrap anyway and the least expensive wood I had, I tossed that away lowered the speed and tried again. Again it (2) was if anything worse and running a second pass was messier on top and still did not cut through.
So I inspected the lenses and the window had a barely perceptible haze so I cleaned that and tried again with the same settings. Not only did it (3) cut through cleanly but with much less smoke, and where slowing the cut did not improve the result, now I think it could be a hair faster,