Greetings! I apologize in advance for the long post but I like to provide full context and thought process so you can really get your head wrapped around where I'm going.

What I'm thinking is that I want to create something in the 48" x 48" range with maybe 6" or so of Z. The base will be a plywood torsion box, upon which I will mount linear rails as the foundation of the mechanics. Custom 1/2 inch aluminum plate gantry uprights, extruded aluminum 80/20 for the gantry with linear rails for the axis. 1/2 inch aluminum plate for the Z axis, again on linear rails. All pretty basic concept. I know, very lacking in details.

Here's the rub, I already have a CNC router. I have a Bob's CNC E3. She's a plywood machine with Nema 17's. 2 drive the gantry as X, 1 drives Y, 1 for Z. X and Y are belt driven Z is ball screw. All powered through an arduino uno. Limit switches are also in place. I want to rob all of this for my new build and drive the new CNC with all ball screws.

The gantry will drive via ball screw mounted, at least in my head, mounted outside of the rails. The Y axis mounted atop the gantry.

Now, I'm pretty much positive there may be a few issues that I'll acknowledge out of the gate. My steppers may be too small, they (arduino) may need to be reconfigured to run them correctly for ball screw vs. belts, and I definitely have to change the parameters when it comes to the actually running the machine as the work areas are vastly different. I'm not there yet.

What pitfalls might I be facing when it comes to structure and steppers? My little Bob's does a fairly good job but, it lacks rigidity and thus, accuracy. It also lacks size. I feel like the NEMA 17s are alright, but everywhere I turn I see NEMA 23s. Is 80/20 extrusion at 1545 profile rigid enough at ~48 inches? Any guidance at this stage would be great. I'm no CAD master, but it'll help me start to draw out what I want to do without having to scrap it a dozen times because my ideas won't work.