An effective quality assessment method for small scale resistance spot welding based on process parameters

With the rapid development of microelectromechanical system technology, small scale resistance spot welding (SSRSW) is ever-increasingly used in electronic and medical devices. Whereas there is limited research work dealing with quality control of SSRSW. This paper treated the U–I (voltage–current) curve as the monitoring signature to explore a real-time and in-situ SSRSW quality monitoring method. First a systematic research on the U–I curve was performed and then five factors extracted from the U–I curve to estimate the weld quality through an artificial intelligence algorithm was proposed. The entire predictions match with their actual results well, showing that the U–I curve is a reliable quality monitoring signature for SSRSW. It can assess the weld strength and nugget diameter in small error on condition that the resistance welding power supply used during the whole welding process can provide linear direct current (DC) or high frequency (HF) current, which is commonly employed in SSRSW.