Awesome print! This is my first post on CNCZone, but I've been trolling on here for years. I would LOVE to see more info about how you've got this all set up. I'm just about to nab a G540 for my Joe's 4x4 hybrid CNC machine that I'm building, but I've been thinking about grabbing a 2nd one to go along with my RepRap Prusa that's currently Arduino controlled with a RAMPS 1.4 board and Pololu stepper drivers.
Are you manually controlling the PID or is Mach3 somehow doing it for you? Is your build bed heated or no? Any chance you'd be willing to share more pictures of your setup and potentially a wiring diagram as well? Forgive me for not knowing Mach3 well enough yet (I don't even have the software yet), but is it also possible for you to share your profile?