Resistance spot welding (RSW) is a widespread manufacturing process in the automotive
industry. There are different approaches for assessing the quality level of RSW joints. Multiinput‐
single‐output methods, which take as inputs either the intrinsic parameters of the welding
process or ultrasonic nondestructive testing variables, are commonly used. This work
demonstrates that the combined use of both types of inputs can significantly improve the
already competitive approach based exclusively on ultrasonic analyses. The use of stacking of
tree ensemble models as classifiers dominates the classification results in terms of accuracy, Fmeasure
and area under the receiver operating characteristic curve metrics. Through variable
importance analyses, the results show that although the welding process parameters are less
relevant than the ultrasonic testing variables, some of the former provide marginal information
not fully captured by the latter.