Big Epoxy Granite machine, Which frame is better ?

[Zorbit]

Removed.

[m_c]

I can't help feeling that the thermal expansion of epoxy concrete, typically twice as much as steel, is going to tie that machine in knots. I'm happy to be educated otherwise.

This was something I failed to find any kind of definitive answer to.
The conclusion I drew, was it can't be that big a concern, given there are some very big EG machines with linear rails mounted to them, with no apparent allowance for expansion. So if it's not off any concern over a couple metres, I doubt I'd worry about it on your typical home build.

As for John's build, what I took from his internal structure, was it was more about keeping things in place during the pour/cast, rather providing much in the way of structural support. Remember in that photo, the outer steel plates are the actual mold and designed to be removed after curing, so they can be reused.

[Zorbit]

Removed.

[JAZZCNC]

I can't help feeling that the thermal expansion of epoxy concrete, typically twice as much as steel, is going to tie that machine in knots. I'm happy to be educated otherwise.

I don't think so.! Some of the best and most accurate lathes and Milling machine in the world use Epoxy granite because of it's thermal advantages and the fact they can build in extra mechanisms ie: running coolant thru the frame to increase this even more. Kern for instance and the Bigger DMG Mori's etc all use EG for there frames.

[Zorbit]

Removed.