On most profesionally built tables the table itself is connected to physical earth ground and the plasma + lead goes to this ground, this point is then ran to a ground plate in the cabinet etc where the shields and motor grounds are connected. This includes PC common and PS commons. All shields should connect one end only.
Also CNC table torches have a large copper braid overall shield which is grounded at the table end.
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.