Abstract: A method of determining deterioration of pressurizing performance of a spot welding, the method having: obtaining reference data that reflect a dynamic state of a servo motor in a case where a movable side electrode tip is operated normally and a wok piece is pressurized by a specified pressurizing force; performing data processing on the reference data to extract a reference characteristic value; obtaining diagnostic data that reflect a dynamic state of the servo motor in a case where a operational state of the movable side electrode tip changes and the work piece is no longer pressurized by a specified pressurizing force; performing data processing on the diagnostic data to extract a diagnostic characteristic value; and determining deterioration of pressurizing performance of the spot welding gun based on the reference characteristic value and the diagnostic characteristic value.

Abstract: A positioning method of spot welding robot having: (A) moving a welding gun with a separation between an opposition electrode tip and a movable electrode tip kept open and larger than a preset plate thickness of a work piece so as to position the opposition electrode tip and the movable electrode tip on both sides of the work piece in a plate-thickness direction of the work piece, respectively, and temporarily positioning the opposition electrode tip at a stand-by position; (B) moving the movable electrode tip in a direction approaching toward the opposition electrode tip, monitoring the current value of the servo motor driving the movable electrode tip, and when the current value exceeds a prescribed value, determining that a distal end of the movable electrode tip has been brought into contact with the work piece, stopping a movement of the movable electrode tip and measuring an open separation of two opposing tips between the movable electrode tip and the opposition electrode tip that has been temporarily

Abstract: A spot welding system including a welding gun with an electrode pair actuated by a servo-motor, a robot carrying the welding gun or objective workpieces and operating to change the relative positions and orientations of the welding gun and the workpieces, and a gun motion controller controlling the servo-motor to actuate the electrode pair to open or close. The gun motion controller includes a motion commanding section outputting a motion command to the servo-motor in accordance with a speed set-value designating a closing speed of the electrode pair, and a set-value adjusting section automatically adjusting the speed set-value to an appropriate value.