Current Distribution Monitoring in Capacitor Discharge Welding

The capacitor discharge welding (CDW) is a resistance welding process that excels through brief process times, low thermal stress, and good automation potential. Nevertheless, potential industrial users hesitate to use the CDW process, owing mainly to the unavailability of automated process control to ensure cost-efficient production and high product quality. For quality assurance, representative values or process curves of the most critical process parameters such as capacitor energy, contact force, electric current, and sink-in depth are monitored. The lack of full significance of this monitoring is indicated by the regular destructive testing of random samples through load tests and cross-section analysis. The essential aspect of the process quality is heat development in the welding zone. The current distribution, as one crucial parameter influencing heat development, is missing. Therefore, this paper presents an in-situ qualitative, indirect current distribution measurement system. The new measurement supplements the process monitoring and analysis, and thus, gain new process knowledge. With better process monitoring and thus understanding, new application areas can be developed for CDW.