arvidb- Welcome! I'm a newbie to this board too. You are going to build a converter for step and direction to ±10vdc? If you can accomplish that, I'll trade you some linear bearings and a ballscrew for your lower axis. When the lower axis rail is fully supported, you are less likely to have vibration vertically. I am retrofitting a bridgeport CNC machine, and the controller is dead, but the servo's and drives are 100%. Plus the machine is only 10 years old. The amplifiers that I have are just like yours. The only low cost controllers out there are designed for stepper (step and direction), not the other industry standard of servo (±10vdc input). I work at a company that tosses out lots of linear ways, ballscrews, even motors and drives. Let me know if you are interested.
By the way, the machine design looks pretty good. One thing that I would suggest is the way you are mounting the duplex angular contact hearings on the end of the ballscrews. Instead of clamping a thin sheet metal looking piece between the bearings, usually they are put into a metal block with a flat bottomed bore, and clamped that way. Usually the bearings are designed to have the inner races touch when you tighten the nut on the ballscrew. The outer races are then squeezed axialy by a clamp plate with a hole in it. If I can figure out how to attach a picture, I'll show you what I mean. For reference, take a look at our catalog. It has lots of tips about servo vs. stepper, and it might help to take a look at some of our standard products. www.neat.com
[url=http://www.cnczone.com/gallery/showphoto.php/photo/329][img]
Take a look if this works!
Neatman