Fuzzy Orthogonal Optimization for Determining the Optimal Resistance Spot Welding Parameters

Resistance spot welding (RSW) is one of the most commonly used form of manufacturing process. To efficiently search for the optimal RSW parameters in a new welding power control scheme to obtain the maximum tensile strength of welded joints, a design of experiments (DoE) using orthogonal arrays has been conducted. However the lack of success of conventional DoE is attributed to two facts that the weld quality is quantitatively measured and level-based evaluated, and the welding expulsion compromises the continuity of response surface, which is an underlying hypothesis of normal DoE analysis. Hereby a fuzzy analysis methodology for the experimentation design, referred as fuzzy orthogonal experiments (FOE) in this paper, has been proposed. With the fuzzification of factor levels and experimental objectives, the proposed method is able to explore the results of arbitrarily given factors without additional experiments, and identifies the varying tendency under condition of discontinuity experimental responses. The FOE application for a specifically planned RSW process presents a detailed FOE analyzing procedures, and yields the optimal parameter settings. The case study shows that FOE outperforms the traditional orthogonal DoE for its minimized experiment numbers and robust response tendency analysis.