Hi Boris -
I’m a fellow Dobot user - I’ve had some luck laser engraving. Can you tell us more?
The first thing I would look at is, when you save your gcode file, what’s the laser movement speed? The default is 1200 mm/sec, and for the 0.5W laser on the Mooz, that’s not really enough to burn most materials. When I did it on wood, I had to slow it down to about 1/8 speed (150mm/s) to get a good, dark burn. I posted on it in this forum, with images to show different print speeds.
What exactly are you able to do, and what is not working out for you?
Aaron