A welding machine that includes a machine frame having an opening permitting access to an interchangeable tooling module installed on the machine. The welding machine includes one or more light curtains covering the opening to disable operation of one or more welding stations on the tooling module if the light curtain is breached by an operator, robot, or other object. The welding machine includes a selector arm attached to the machine frame at a location between a first end and a second end of the opening. The selector arm can be moved into and out of position at the opening to selectively define either a single light curtain across the opening or a pair of adjacent light curtains that permit separate operation and access to separate welding stations behind each of the two light curtains.
