Patent ID: 8513560

Claim:
A method of spot welding comprising: obtaining access to a spot welding system, including: a spot welding gun having a pair of electrodes disposed oppositely to each other, and a servo motor for allowing the pair of electrodes to approach each other and separate from each other; a robot for holding either one of the spot welding gun and a workpiece in a manner movable relative to each other so that the workpiece is disposed between the pair of electrodes of the spot welding gun; a first detection section for detecting a torque or rotation velocity of the servo motor; a second detection section for detecting positions of the pair of electrodes; a mode switching section for switching, in response to a switching command by manipulation of an operator, an operation mode, that is a control mode, of the spot welding system between a spot welding mode for spot-welding the workpiece and a position correction mode for correcting a spot welding position of the workpiece; and a processing section for performing a spot welding process in the spot welding mode and a position correction process in the position correction mode, controlling the spot welding gun and the robot with a spot welding gun and robot control section that is part of the processing section with the operation mode switched into the spot welding mode by the mode switching section so that the workpiece is spot-welded based on a workpiece position set in a predetermined working program and controlling the spot welding gun and the robot with the spot welding gun and robot control section with the operation mode switched into the position correction mode so that only one of the pair of electrodes abuts against a surface of the workpiece; determining whether only one of the pair of electrodes abuts against the surface of the workpiece or not with an abutment determination section that is part of the processing section based on a value detected by the first detection section in the position correction mode; and a computation section for computing the workpiece position using a computation section that is part of the processing section based on a value detected by the second detection section when the abutment determination section determines that only one of the pair of electrodes abuts against the surface of the workpiece.