I bought into his rationale hook, line, and sinker initially and very nearly convinced myself I should sell the 3060 (3' x 6') extrusion I just bought, go find a welder, and start fabricating a 'real' beam out of steel. The basis of that person's logic was that 8020 doesn't have a continuous 'skin' and the t-slots greatly reduce its ability to resist twisting forces. I read a couple days ago a post where someone asserted that 8020 t-slot extrusions are terrible in torsion compared to steel. There seems to be fairly healthy debate on the Zone about 8020 vs. Unless you're cutting strictly parallel to the beam's long axis (or using a non-contact tool like a plasma or laser), torsional loads resulting from the spindle load inducing twisting in the beam via bearing reactions is something we should think very carefully about. One key aspect of any moving gantry machine is the gantry beam, what it's made of, and the loads it can resist, especially in torsion.

I'm in the early stages of designing my second router and focusing much more closely on performance aspects after lessons learned on my first machine.

8020 t slot wall structure