Adaptive resistance spot welding method that reduces the shunting effect

Abstract

A reference-based adaptive resistance spot welding (RSW) method intended to reduce the shunting effect in short-pitch (≤40 mm) RSW is proposed in this study. As the weld pitch decreases, the nugget diameter and dynamic resistance level concurrently decrease by an amount equivalent to the increased shunting effect. Based on this fundamental relationship, an exponential model capable of predicting weld pitch as a function of dynamic resistance was estimated. Next, the relationship between the nugget diameter and the heat input as a function of weld pitch was investigated, and a logistic growth model capable of predicting heat input compensation was established. These exponential and logistic growth models form the basis of the proposed RSW method’s control algorithm. The proposed RSW method compensates for the heat input loss caused by the shunting effect by adjusting welding time in real time under a constant current control until the predicted heat input compensation is obtained. Experimental results indicated that the RSW method proposed in this study concurrently increased the nugget diameter and decreased the shunting effect in short-pitch RSW compared with conventional welding method results. This finding suggests that the proposed reference-based adaptive RSW method is effective in reducing the shunting effect in short-pitch RSW.