I just wanted to share the settings I’m using for engraving some non-proofgrade vegetable-tanned leather, with a high-detail black-and-white (not grayscale) image. It’s a vector image, not rasterized.
I experimented with faster and slower settings, because I wanted the job to go faster. The speed made less difference than the lines-per-inch. A higher speed (with higher power) sacrificed a small amount of accuracy in outlines, but the benefit was a more consistent appearance of the engraved area. I finally settled on speed 1000, power 30, 450 lines per inch.
My experience is to adjust the needed LPI, go to max power, and then go to a high enough speed to do the job. This needs to be modified if the engrave is narrow, as high speed can get minimum returns below zero. And as pointed out it is only really relief engraving that needs the maximum power. As well Leather is perhaps the material least likely to show the plowed field effect of a low LPI as well as the least likely to show a decent relief design. So a dot matrix would seem to be the way to go. adjusting the density would be needed however.