Design for 1800x800x80 wood router

[jimbo_cnc]

No interest last time, must have been such a brilliant design it didn't warrant comment :)

I've now made the decision to get a bigger machine, so it's time to explore the various possibilities and either import, buy, build, or get someone to build me something.

I'd like a machine that is stiffer than my cheap 6040 for cutting plastic, and also big enough to cut 1650x590 wood panels. I'm thinking of making do with a 6090, but this thread is for exploring a machine sized for the job (and some spare width for larger designs that the 6090 won't be ablo to do), ie 1800x800.

So here is a general layout.

The things I need help with are making the decision on construction materials and methods. Welded square steel tube, or aluminium sections are the two main choices.

Also single or twin ballscrews on the long axis? I think I prefer the twin design and the base will be easier and more compact, but I need to work out the cost delta. The single ball screw makes it easy to undermount the rail, if that's a good thing?

I can get a steel frame welded quite easily, but then how to align the rails on it?

With aluminium section, I guess you rely on it being straight? Then the question is how to square up the frame. My friend suggested poor a concrete bed and bolt it down to that to get it flat (equivalent to epoxy method).

I will start to gather some prices for parts, hopefully people will then comment on how to do it cheaper.

And, before anyone asks; No, I don't want to make it 1200 wide :)

[jimbo_cnc]

The concrete base idea would be something like this.

It looks like a lot of work and materials now, but if it would work, it does require much skill.

[jimbo_cnc]

Has anyone done this?

Weld up a steel ladder frame, bolt strips of acetal to every member, and take it to a friendly wood cnc place and get them to skim it flat. Also drill some locator hole where you will tap and thread later.

If you had a flat surface, would that be enough to ensure a straight linear rail? ie can the rail be reliably attached to the aluminium profile and be straight, using countersink washers and screws or something like that?