Thanks Ed, good to hear from someone in the "biz" already.
I have some small motors (400 steps/ rev), but they have quite a bit of torque in two phase mode and shouldn't have any problem moving a lead screw even with the Z axis.
The only reason I didn't like the thought of leadscrews was even if I use 1/4-20" then I get 400 steps * 20 threads/inch which is 8000 steps / inch. Which means the motors would have to move very fast to go any quicker than 1 inch/min. (In fact I don't think they can handle it well using KCam software anyway..) This is offset by the fact however that I don't think I'll be able to go too fast anyway being that I'm cutting foam and it's supposed to be slow and cool ! So it might work out to be ok !
I'm thinking I'll probably try to go with some rollerblade bearings for now as well since I can make it just like the normal big machines (with adjustments on the end of the pipes).
I was actually thinking of some different bearing arrangements if using drawer slides, just using one for X and one for Z instead of two opposing. That would eliminate aligning problems. Z lead screw would be pre-loaded by gravity so backlash would be eliimated in Z, so I would only have to worry about X..
Thanks for your feedback
-niko