| 摘要 |
PROBLEM TO BE SOLVED: To obtain statically determinate welding force equal to the target welding force without depending on the speed of an electrode at the time of pressurizing operation. SOLUTION: Spot welding is executed while pressurizing a work between an uppdr movable electrode 5 and a lower stationary electrode board. The upper movable electrode 5 is linearly moved toward the lower stationary electrode board by converting the rotation of an electric motor 9 into a rectilinear motion by ball screw means 6 and the work is held by constant wedding force between itself and the lower stationary electrode board. At this time, the amount of the current to the electric motor 9 is controlled so that, for only short time in the initial stage of pressurization, welding force higher than the target welding force by a fixed quantity is taken and, after that, returned to the target welding force.
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