[steve123]

Okay, I'm confused then.

If you're going to weld the frame and not stress relieve it, aren't you going to have to deal with it warping? Or are you just planning on your table slab (concrete, granite, whatever) being rigid and flat and wide enough to mount your gantry rails on it? If you mount the rails to the (welded, poss. warped) base, they won't be aligned with the table...

Erik

I wasn't going to stress-relieve the base, because I don't know how to move over 1200 lbs somewhere and get it done. It would still not be exactly level with the rails anyway. I plan instead to weld all of the base in short beads to minimize warping. Then I will wait a week or two, and pour self-leveled X rails AND self-leveled base beams. The grid of base beams will be a pain to make all the dams for, and keep leak-free, but I have some ideas.

PS: I highly recommend the book "High Performance Machining" by Arnone. Excellent discussion of many of the design/construction issues that machine builders deal with.

Thanks Erik. I just purchased that from Amazon.