A new hope: Epoxy granite and steel.

[pippin88]

Well that depends on application and what stiffness is required. In this application it doesn't need high stiffness but does require the height. However, I can tell you it's still very stiff.

I will be building a much larger version that will work the same with lifting gantry but with much more bracing using 10mm wall tubes rather than 5mm used on this.

I can't see how the stiffness loss with a slot is worth it.

The below shows two identical columns, except one has a slot cut in it. There is 2.36x as much deflection with the slot.


Bellows don't compromise rigidity.

You could but it will look crap and require you have a high ceiling.
Also it won't work very well because the gantry could and IMO will definately rack when plunge cutting at the outer edges. Disaster waiting to happen IMO.

The design I've shown only uses a single motor connected to the screws with belt/pulleys so it's only one extra screw so no big expense in the grand scheme.

Who cares what it looks like?

High ceiling - maybe. Not that high. Depends on what level the base of the machine sits...

Racking is a consideration. Depends on width between rails and bearing spacing along the rails.

I agree, ball screw expense is not the biggest consideration (though starts to get much more when you use high quality bearing blocks etc). I'm thinking about screw mapping and linear encoders - much harder with two screws.
Belt stretch is a concern for a long enough belt to link those two ball screws.