Hello Pierre

One of the causes for banding, mostly when engraving big continous images on granite, is just the laser losing power.

When that happens you have to increase the engraving speed and laser engraving power. You can test this if it works.

You can also check the laser power supply to see if it's working with the correct voltage.

By the way, i engrave with a synrad J48-2 25 wats laser and a Camtech machine.