OK, I have a very large (18" X 18" x 18") print volume printer. Custom built, RepRap based. I see shockingly consistent drift on the Y axis. What I have tried so far: 1) Tighten all the mechanical components and clean, including and especially the screw backlash arrangement. All axes are driven by mechanical screws posts, there are no belts on my printer, so it can't be belts. 2) Tried drivinby DrDave - Printing