When I use my Atomstack A5 Pro to cut out a 4mm circle, it is a tad bit oblong. Took a brush to the laser to dust it off and still occurs. Cutting out 3mm maple wood. Might I be trying to cut out too fast or simply a resolution/limitation of this machine?
laser dot is a bar and the kerf in one direction is bigger than the kerf in the other direction
X and Y axes need to be calibrated for steps/mm
backlash in your system
Run a few tests by engraving circles and squares of a given size and comparing designed size vs measured size. Make this relatively large as that will reduce impact of measuring error.
Pretty close now. About .25mm off. My process was to create a 50mmX50mm box, make the line and then measure with calipers. Circle is look more proper now. Might get back in there and try to dial it in a bit more.