Process Monitoring of Resistance Spot Welding Using the Dynamic Resistance Signature: A technique was developed that allows for complete monitoring of the spot welding process including weld strength and electrode tip wear

The quality of resistance spot welds used to manufacture automobiles is critical to their safety. Monitoring of spot welds during production is, therefore, a high priority for ensuring quality control. Interactions between the mechanical, thermal, and electrical processes involved in resistance spot welding (RSW) make the prediction of weld quality difficult. This complexity is confounded by the changing process variables in RSW that must be monitored in-process to monitor the quality of spot welds, such as electrode wear, physical setup, and surface contamination. This paper presents a complete process monitoring method for RSW, including models for weld quality and process condition. Information is extracted from the dynamic resistance signature (DRS) collected during welding. The method allows for quick, in-line detection of faults, identification of the responsible variables, and diagnosis of the cause of the abnormal behavior without requiring parts to be removed from the production line.