Spot welding method, spot welding machine and spot welding robot

Abstract

A spot welding apparatus capable of detecting a defect such as a missing of works or a bite of a foreign substance reliably before a welding operation. A spot welding method for welding superposed works (6) which are clamped and pressed between a stationary electrode (3) and a movable electrode (4) and are fed an electric power between the electrodes (3) and (4). The method has the step of: prior to an actual welding operation, measuring a position of the movable electrode (4) when the works (6) are clamped by the electrodes (3) and (4), and storing the measured value as a reference value TH; measuring a position TR of the movable electrode (4) when the works (6) are clamped by the electrodes (3) and (4), at the time of executing the actual welding operation; and comparing the position TR and the reference value TH thereby to execute the welding operation, when the position, TR is within a predetermined range with respect to the reference value TH, and to issue a warning and interrupt the welding operation, when the position TR is not within the predetermined range.

Dependencies are inferred from the claim text.