Small rigid router - Design advise needed

[JAZZCNC]

Not sure I understand what you mean about the spare IOs. I do have spare inputs available on my controller but i dont want to rely on mach3 alone to stop everything or is that not what you mean?

What I mean is that there's no difference between Mach3 inputs and Arduino inputs Both are using and relying on Computers for safety.(BAD news) So if you had the spare inputs you may have well just used I/O on controller.

Regards the Drive fault signal and Relay then you only needed 1 relay and wire the drive fault signals in parallel so if any drive faulted it turned on the relay. The relay NO or NC contacts would be used to control other things like E-stop relay and send signals to control saying fault happened.!! . . . Much safer.