Wireless laser welding monitoring for automotive application

For quality assurance in the manufacture of automotive parts, the integrity of the laser-beam welds joining steel parts must be monitored. A primary concern is to detect weld defects fast, reliably and cost-effectively. Therefore, a considerable number of on-line inspection systems have being developed to improve weld quality and reduce overall costs. All the systems, for monitoring the photonic emissions from the weld pool, adopt measurement schemes in which wired sensors output a voltage signal (mV) that depends on the beam power and weld characteristics. The DC level of this signal is related to weld penetration, while AC portions of the output can be correlated with surface irregularities and part misalignment or contamination. During the last years, the development of the wireless data transmission technology has prompted monitoring folks to consider alternatives that reduce wiring costs, make connections not feasible previously and retrofit more measurement points cost effectively as well. This paper presents a prototype wireless monitor for laser welding operations that can sense irregularities in the welded seam and weld penetration. The weld monitor is designed to be simple, low cost, and able to withstand a harsh manufacturing environment. The prototype system has been used during the welding of structural parts of car doors to explore the relationships between the weld characteristics and the weld monitor output.