[CarveOne]

Ok, one more idea to consider to strengthen the uprights.

Make a second pair of angle irons that fit against the existing uprights and tack weld them together every few inches. Almost as strong as box tubes and easier to implement.

One more mechanical note:

If your z axis motor seems to be sluggish when moving upwards but not when moving downwards it may be the combined weight of the steel slider assembly coupled with the weight of the router (assuming that you will be using a full size router). I don't know anything about the motor torque and lead screw you will use yet so I'm just guessing at this point. Lifting a lot of weight against gravity can be an issue in steel designs. It can also cause excessive wear on the lead screw and lead nut.

I don't see anything else to point out at this point except that my second machine will be steel construction as well and I have already researched some of the things to look out for. These suggestions seem to be the major issues to consider.

Your wiring does look very neat and orderly as others have pointed out. I noticed that you twisted the related wires. What this does is help to minimize cross-coupling of unlike signals in a bundle. It also helps to twist some of them clockwise and some of them counterclockwise in the bundle. The tighter the twist the more capacitance the pair of wires will have per foot. This coupling capacitance can be a signal distortion problem for higher speed digital signals.

Best of luck with the rest of your build!

CarveOne