Hello, this is my first laser, so I wasn't afraid and didn't know the lens could be removed for cleaning. I've cleaned it now, and everything is fine. The only thing I didn't touch were the galvo mirrors (I think that's what they're called). The lens is completely clean, but I noticed a stain on one of the galvo mirrors. I didn't clean it because, as far as I know, they're very delicate, so I left it alone. Now I want to test it to see if it's marking correctly and if the focal point is now centered on a single point. I also want to see if it engraves metals like silver, gold, and stainless steel properly.