Starting to design out my build, looking for critique

[Chrono]

That cleared things up a lot, thanks! I gotta admit, for a second there I thought the aluminium profile construction was "out of the question" entirely, so to speak, so I am relieved on that end

I also thought about putting in some more support pillars, so I will do that. They are so short anyways, that they don't cost enough to not put in. regarding a crossbar, I could easily put one in in the back, without even impeding X travel, since the gantry's body will sit on top of it, and it will run out of rails before the spindle would even get a chance of touching it.

You also put in angles in the middle pillars. I definitely see their point, but I am looking at them protruding into the machining area, so I might try and make them removable, with accessible screws, so I can put them there for smaller projects, and take them off, when I need the space. That way I get the best of both worlds, so to speak.

Also, regarding the distance between the bearing blocks on the X: That is one of the parameters I can just change on-the-fly, so changing that is easy-as-can-be :D I am mostly leaving it as a kind of place-holder while I am working on getting everything into place. Afterwards I just need to open the variables panel, and go to town dialing everything in.

Finally, on the topic of the thin plate, and the associated double-stack of rails, with one opposite linear rod bearing: It is not that much about building tolerances (I mean I am not perfect, so there will be those), but also things like thermal expansion, and so on. I am going off of the one lecture in mechanical engineering I got in my electrical engineering course, but with the linear rails on both sides, you would enter statically-overconstrained territory, which is exactly the reason for me to go for the steel rod and linear bearings, exactly because they cannot take on torque. however, if this ends up not panning out, changing the lower rail over, would be quite easy, since all i would have to do is cut down the gantry extrusions by 7mm (which the linear bearings are higher by, compared to the rails and bearing blocks), or shim it with another plate, and swap in one of the rails, not a big hassle.

And I found a picture of the Zeiss machine I was talking about:

As you can see, it has a similar design, with rails on existing on the right, while the left either rolls on the table or hovers on it, I cannot remember if the hovering was another machine, though, and a quick search did not throw up any info. Either way, looking at the YZ-Plane, one end is fixed, while the other is allowed to expand/move. Of course, that does not mean that it works the same for me, but I thought I would post that for illustratory purposes :)

I also plan to add some slits in the plates themselves, serving as holes for potential cross-supports, should it turn out that they are, indeed, too bendy. I will attach a picture hereafter, looking at the right plate, with such a support in vibrant pink. I am afraid that picture can explain this much faster than I could in words. Those plates should serve to add further rigidity, in the same sense as the bends all around the Z-Axis do, and if I find I need them, I can put them in, weld them in place, and go from there.



(also seen in the picture, in the front left of the machine, the WIP of new angle plates. The right is not in yet, because I still need to move the right ballscrew vertically in between the two rails)

What do you think of those measures to address these problems? Is there anything else I should be doing to increase the rigidity?