by andrewblanejr » Sun Oct 16, 2011 11:56 pm
the 2020 extrusions will bend after a while if not supported. I'm not sure the limit, there are some real technical measuresments of stiffness, they are usually published and available for any type of extruion. I just don't know how to make sense of the formula yet. you should look into this, you dont want your gantry sagging.
also my understanding is that the mirrors tend to get harder and harder to align the larger you go. They must all be on the same plane, which if your frame sags or is misaligned even a little bit makes a larger difference over a longer length. Also the angle of the mirrors becomes mroe important, an minute adjustment in angle may not be noticed in a smaller system but it could amplify over distance and be critical in a larger system.
good luck!