I have been wanting to build one of these for a while. I have looked at just about every type of machine out there to get ideas of what to make and how to do it. I would find a setup I liked until I read about all the problems he had with flex, movement, tracking, etc. I decided on another, but the cost was too much for my limited budget (as close to $0.00 as possible). Surplus parts and items on clearance pushed me to the “skate bearing on a tube” designed for the x and y axis. The use of drawer slides is generally ruled out as unacceptable, however I am planning a small Z axis with a flex cable driven spindle – the small 2″ slide should work for now.