Monitoring Nugget Size of Micro Resistance Spot Welding (Micro RSW) Using Electrode Displacement-Time Curve

Abstract

The objective of this work is to investigate the relationship between nugget development and electrode displacement curves during micro RSW of stainless steel sheets. A DC transistor type micro RSW machine equipped with a real-time monitoring system was employed for this study. A laser displacement sensor was used to detect the displacement signals in the movement of upper electrode. This research can provide references for monitoring and control micro RSW quality using maximum electrode displacement. The results showed that electrode displacement increased rapidly at the initial heating stage of welding, and then at a reducing rate under normal cooling stage. The maximum electrode displacement is proportional to the weld current and is inversely proportional to the electrode force. An electrode displacement curve is an ideal monitoring signal can reflect the formation and growth of a nugget during micro RSW.