your sort of thinking the wrong way round with this.

You may have a problem with interference from many things in the workshop, and isolating them all would not be possible.

Its the data lines between PC>BOB and sometimes BOB>MOTORS that you need to make sure is insulated from everything else, swap out that parallel for another one.

Its also the only place apart from the BOB, that you can interfare with the motor timings and estops and motor direction at the same time.

Let me add this though, i have never worked with plasma gear so i dont understand what fields that creates, or what extra current/dump loads it uses. So there may be something obvious am missing