Quote Originally Posted by Radu_Andrei View Post
Thanks for the reply.
I don.t get why is the contactor involved in all of this. When you interrupt the signal wire (open the contactor), you also kill power to everything else, except the BoB. Why? Why not use just Bob input terminals?
The BoB input alone is not reliable enough to be used for an emergency stop.

Estop, the emergency stop, that big red mushroom button should be there for emergencies. Water is leaking through the motor electrical connections and on the floor so you could be electrocuted or something in the machine catches fire ... You will be hitting the Estop while running for the door or the fire extinguisher. In those cases you want to kill all power to the machine with that button.
The reason I've put the limit switches on the same loop with the Estop is that I have the sensors for the limit. If the sensor is not stopping the axis, then something should be really bad with mach3 or the motor drive and I want the end switch to stop everything before hitting the end of axis travel.

For minor "emergencies" like loosening the workpiece or hitting a clamp you have the mach3 Stop or Feed Hold buttons.