Is there a reason all the CNC router builds have 2 motors on the Y axis? I have found some designs elsewhere that have a single center mounted stepper. Is it a racking concern or torque? Something simliar to this: http://www.instructables.com/id/DIY-CNC-Router/step18/Y-Axis-Assembly/ I was contemplating using a ballscrew in the center and a single stepper.
Yes, racking is an issue but as most of the CNC designs move the gantry rather than the platform, there hasn't been much effort focused on a solution. It's fairly easily overcome though. Just run a center rail down the middle underneath the platform with guide wheels at both ends of the board.
