Quote Originally Posted by JAZZCNC View Post
Why did you have concerns about DOC.? It doesn't get any better than with this design for a machine with a larger cutting area as the Z extension is never any longer than the tool length, and that is at any Z height.
Some of the largest Gantry mills in the world use this exact design. If you build it strong enough the only limit on DOC will be spindle power.
The main DOC concern was that when I put different pieces with different height onto the vacuum table I'd hit the higher ones with the vertical beam. Like machining the bottom and top piece (http://www.jt-precision.com/uploads/...7293225867.jpg) one after another without actually having to go and change the piece. Sure I could put the higher one to the front, it would work, but knowing me, I'd switch the 2 unconsciously and mess some part of the machine.

Anyway, do you recommend a ballscrew on each column or one thicker in the middle?