Determining the correct laser settings for engraving slate involves several key factors. Firstly, identify the type and thickness of the slate you are using, as different slates may require different settings. Begin by setting your laser engraving machine to a lower power and slower speed, as slate is a hard material that can crack if too much heat is applied too quickly.

A good starting point is around 30-40% power and a speed of 100-150 mm/s. Perform test engravings on a scrap piece of slate to assess the results. Look for a clear contrast in the engraved areas without excessive chipping or cracking. Adjust the power settings in increments of 5-10%, while keeping the speed constant, to find the ideal balance.

Additionally, consider the frequency settings, as a lower frequency can provide a better finish for detailed engravings. Finally, make sure to clean the slate surface before engraving to remove any dust or oils that might affect the final result. Once you have found the perfect settings, document them for future reference.