Limit switches etc.
Where ever possible have your limit switches Normally Closed
That way, when in normal operation they short out induced noise.
Put a 100n capacitor across all low voltage operated switches, so that the switch contacts get a high current zap from the capacitor. This helps to keep the contacts clean, and makes the wetting current much closer to what the manufacturer specifies. The capacitor needs to be close to the switch, so the pulse current is not lost in the wiring, and stops these current pulses interfering with other circuits.
DO NOT USE the 100n capacitor method with anything other than mechanical contacts. It can cause opto-slot switches to not work properly, or even damage them.
Using NC switches often means you must put a number of them in series, so trouble shooting can become more difficult. At least the machine will fail safe if a wire breaks.
Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.