Came across this recently - it has 1m Z travel. I can't quite make out the gantry / Z axis arrangement, probably double beam gantry with box Z inside?

But it is also 58 tons so not going in that transit!

http://verticalmachiningcentres.blog...ng-centre.html

What Jonathan means is that total stiffness as seen by the cutting tool is everything between the end of the tool and the bed - the long way round! By this I mean back up the spindle, any offsets, gantry, ballnut stiffness, ballscrew axial stiffness, ballscrew AC bearing stiffness, frame stiffness, bed stiffness, clamping arrangement stiffness, and the stiffness of the part being cut. It all adds up.
Are you going to lock off the bed? If it is just held on the 4 ballnuts then there is 50 microns vertical freeplay right there. Or is it going to be very, very heavy?