To achieve the evaluation of the quality of resistance welding without causing the expansion of equipment.
In a step (S120) of determining the quality of resistance welding from the change mode of interelectrode resistance value upon welding, a resistance waveform showing the interelectrode resistance of a welding gun is grasped from a current value to be energized to the welding gun being a control parameter of a resistance welding equipment and the interelectrode voltage of the welding gun being a measurement value, and welding quality is determined. Further, in a step (S130) of determining welding quality from interelectrode distance before welding, on the basis of the interelectrode distance before welding, the presence of a plate gap before welding is grasped, and, when a plate gap is determined not to be present, the determination of non-defective unit in the step (S120) of determining the quality of resistance is adopted as final quality evaluation from the change mode of interelectrode resistance value on welding. Further, when a plate gap is determined to be present in the step (S130) of determining welding quality from interelectrode distance before welding, it is determined that the accuracy of the determined result is lacked, and the final quality evaluation is determined as a non-conforming article (S160).
CHIKAGAWA HIROSHI
FUSHIBA YUICHI
TSURU KEISUKE
Miyazaki Yoshio
Kaoru Onozuka
Akio Tagami
High Masahiro
Tsutomu Kato