Re: CNC Drill Gantry/Router Recommended OEM's for Steel Panels
What is your budget? That will dictate the best option.
Your item 7 might be a problem. As far as I know there is no machine control software that will directly accept a file from AutoCad or Promise-E. Normally save as a DXF and then use a CAM program to generate the G-code to run the machine. Not a big problem but that's the way it's done.
I am very familiar with what you are wanting to do, in fact I'm doing a panel tomorrow on my mill. Both the back panel and the door cutouts for instrumentation. In this case it's a 24x24. I don't know what steel grade they make panels out of, but it is a PITA to machine.
If I were going to set up to do up to 72x72, I would buy a heavy, used industrial router and put a milling machine head on it. Router spindles turn much too fast for what you want to do. There are several ways to handle the tool changing. In this case I would probably make a rack style. Unless you can find a large gantry mill or huge VMC, you are probably going to have to modify a machine to fit your needs.
If you can find Thermwood router, that would make a good base. Those things are built like a tank.
Jim Dawson
Sandy, Oregon, USA