Statistical investigation on resistance spot welding quality using a two-state, sliding-level experiment

Quality, variation in resistance spot welding is a major concern in the aut omotive industry,. The relationship between weld quality and various proces s conditions, including abnormal process conditions, has not vet been syste matically studied. This paper investigates this relationship using a newly developed two-stage, sliding-level experiment. In the experiment, welding c urrent is treated as a ''slid factor " whose settings are determined based on those of other process variables. Engineering knowledge is applied in st atistical model selection, From the analysis, it is found that abnormal pro cess conditions, such as axial misalignment, angular misalignment, poor fit up, edge weld, and electrode wear, significantly affect weld size and thus cause large variation in the weld quality, Although they may help increase the weld size in some cases, abnormal process conditions generally lead to a less robust process. In order to minimize the effects of the abnormal pro cess conditions, a robust parameter design is formulated using the statisti cal models developed from the experimental data. The analysis suggests that high current and large electrodes should be used for reducing the weld qua lity variation. Developed in this study. the new experimental design and an alysis procedures can also be applied to other processes, where the process variables are inter-dependent.