Right now I have 20x20 extrusions in my 1meter tall/300mm bed delta with metal Robotdigg corners. Even with an all-metal frame the twist factor is not very stiff.
When I made this machine they were not available but now I see several metal-corner options for thicker towers. The question is...which is better for me?
The 30x30s seem like they would be the best: 900 cm^2 cross-section vs 800 cm^2 cross-section of the 20x40 extrusions. They are also more symmetric to loads.
On the other hand, the 20x40s would fit my current wheeled carriages I custom machined and don't want to waste the effort. 20mm is also a more standard dimension for future proofing.
But as accurate as my home-made carriages are, they are heavy and one day I should switch to recirculating-ball rails anyway. My delta is almost completely free of printed parts (the endstop switches still use printed mounting blocks, oh my!)
Any experience or thoughts you can add to my conclusions would be helpful.
thanks