Cast aluminium gantry router

[Jonathan]

I can cut this to length, machine the ends then top and bottom for the rails and wherever parts are to be mounted. I might even bolt 2 castings back to back and make an "I" beam from them.

Don't bother with the I-beam idea - rubbish torsional stiffness.

[routercnc]

Don't bother with the I-beam idea - rubbish torsional stiffness.

True, but to pick up on your initial idea of twin beam arrangements you could arrange them like this:

[] instead of ][

[] has similar vertical stiffness to ][, slightly better fore/aft stiffness, and massively better torsional stiffness. If you cast it then you can include baffle plates at intervals so long as you also bolt through these as well.

A simpler alternative is to do |] where ] is the cast part (with optional internal baffles or ribs) and | is a simple closer plate.

Still lots of effort all round but they are possible configurations and much better than just ].