The US has imposed a law to have air bags to protect driver and front passenger in the vehicles. Many vehicles are equipped with additional air bags for knee protection, side impacts, roll-overs and rear passengers. Besides the air bag module, an air bag system consists of crash sensors, passenger sensors, a control unit, seat belt pretensioners, a warning light, and a wire harness to link them all together. Air bags are assembled with a variety of processes, including welding, clinching, and riveting. Igniters are welded with a pulsed Nd:YAG laser delivered through fiber optics. The laser creates a hermetic seal and provides strict control over the depth and width of the weld. Assembling air bags also includes measuring and dispensing the gas-generating agents, which is accomplished with automatic equipment in an enclosed space. In addition, X-ray inspection systems check finished assemblies for completeness and loose parts that could turn into projectiles.
