Construction Idea Discussion: Large Steel tubes + non shrink grout = win?

[routercnc]

Hi Noplace,

You can weld large tubes together although you need to manage the distortion. Large tubes cost proportionately more so budget is the main 'feasibility' limit. Larger tubes are disproportionately stiffer than smaller tubes so a small increase in size gives more in stiffness. I've also seen some pretty large wall thicknesses used which although isn't the most efficient way to gain wholesale stiffness levels, it does help distribute any small / point loading forces such as locally where rails are mounted onto surfaces etc.

Anything which increases the weight of the bed or non-moving part is beneficial - assuming your floor / table can take the weight! Anything which increases the weight of the moving parts is subject to a study of the electronics required to drive it.

Filling the voids:
Cement is probably not wise as it contracts when set leaving a small gap all around.
Epoxy is possible although it will get hot in large quantities and would work out very expensive.
Kiln dried sand is cheap, easy to re-use, and provides good damping. This is probably your best bet.

Moulded design:
This is very possible and is what Chaz is looking to do (Thor, or should that be Zeus). Plenty of examples on YouTube etc of granite type designs.
The ones I've seen cast in some steel members leaving part of it sticking out. This forms the basis for attaching the rails. Milling, scraping or epoxy are then options for getting a datum surface.