It’s from the air assist blowing smoke across the wood. Ultimately it’d be better to have the air blowing straight down instead of at an angle, but due to the JTech magnetic shroud that’s not possible. I’ve reached out to JTech to see if they sell a magnetic attachment without the shroud, or if I can cut the current shroud apart to remove the annoying cross piece, but it’s a holiday weekend, so I don’t expect a quick reply. Some of that staining can be removed with a wire brush though, so it’s not a show stopper, just irritating. I refocused my laser to extend the beam a bit so there’s more room for the air assist, and I don’t use the air unless I plan to cut through, so at least the engraving is clean.
Dan