Richard, I appreciate the confusion--I should have been more specific. I have both a woodworking and machining background before becoming an engineer, so I tend to interchange router and mill when perhaps I shouldn't.
By "vertical" I mean only that the bed of the proposed
CNC router is oriented vertically with a horizontal spindle. The X-axis still runs parallel to the ground and the Y-axis runs vertically. Think of something more like a vertical panel saw.
The obvious (and perhaps only) advantage to such a design would be floorspace. I'm guessing it would take up only about 1/3 the square footage of an equivalent capacity traditional horizontal bed machine.
The disadvantages are, perhaps, a bridge too far. The Y-axis drive mechanism now how has to support the mass of both Y and Z when accelerating/decelerating. I'm guessing there may be a stiff penalty to pay, either in cost for the Y-axis drive/power supply or in performance if the costs aren't paid up front.
Hopefully this clarifies what I'm considering. Thoughts?
Thanks,
Tom