A locking and fail-safe system can ensure proper installation of a lens assembly in a laser welding machine. The laser welding machine includes a laser head, a lens assembly, and an alignment tab operatively connected to the lens assembly. A device can be operatively positioned relative to the laser welding machine. The device can include a spring pin member with a movable slide pin. In a locked condition, the spring pin member can be positioned such that the slide pin is received in an aperture in the alignment tab, indicating that the lens assembly is properly installed and locking the lens assembly in place. A sensor can be used to determine whether the spring pin assembly is in a correct position, location, and/or orientation. The laser welding machine can be disabled if the spring pin member is not in a correct position, location, and/or orientation.