Quote Originally Posted by JAZZCNC View Post

Regards the ballscrews then it only works with one on each column. . . . How could you fit a central ballscrew and still have the material move thru the opening.
I like your new machine, though I think hiding the ball screws like that reduces stiffness too much by cutting into the tubes.

You can have a single central screw on a lifting gantry machine. The screw moves up and down with the gantry. Nut it attached to the fixed top cross beam. Either rotating but with servo attached to fixed cross beam, or rotating screw with Z servo moving up and down with Z.
Pros: Single screw (screw mapping, servo tuning, cost). Cons: A bit trickier to implement. Will have screw sticking right up high when Z fully up.