I would not weld much of anything except to the extent of welding up custom angle brackets that you will need to bolt the aluminum together.

the reason is simply for future re-design and re-use, flexibility. also if you intend to bolt the linear rails directly to the aluminum, then making a mistake and welding the joint 1 degree off will be a real pain to correct.

welding the aluminum will not add any rigidity to the system if the bolts are sufficient to prevent the bolted joint from slipping under load. a grade 3 1/4-20 bolt can put 2000 pounds of clamping force, and if you have 4 of them per corner joint, that's 8000 pounds of force, which means 2000 pounds at least would be required to make the joint slip. if the joint slips you'll have to deal with the bolts loosening over time.


depending on which alloy of aluminum you have, it has almost no intrinsic dampening. so i would recommend not mass loading the system.. but rather build your aluminum structure and glue the base of it with silicon or butyl rubber to granite counter top remnants. the silicon or rubber will provide the compliance needed to prevent temperature changes from warping it, and both are a fairly good dampening, with the granite providing the global stability and mass dampening

Granite has about 2/3rds the modulous of elasticity as does aluminum and the same density, but it has a dampening coefficient that is hard to get elsewhere.

you can glue the aluminum together rather than weld to turn your 50mm extrusions into 100 mm extrusions. no warpage.. you could even shim and clamp them to get them globally flat to .001 while the epoxy cures.