PURPOSE: To obviate defective welding even if the speed of circular electrodes is changed and further, materials to be welded are changed.
CONSTITUTION: A position detector 20 and a speed detector 21 to detect the position and speed of the circular electrodes 4a and 4b are provided and a welding current detector 17 to detect a welding current of the circular electrodes 4a and 4b existing in the position and speed is provided. Signals from the position detector 20, the speed detector 21 and the welding current detector 17 are compared and calculated with a welding current set value set corresponding to the position and speed of the circular electrodes 4a and 4b and a control part to output a welding current value so that the welding current detected by the welding current detector 17 is coincident with the set welding current is provided. Consequently, since a position factor and a speed factor of the circular electrodes of seam welding and a condition of the welding current are satisfied, even if the speed of the circular electrodes 4a and 4b is changed and moreover, the materials 3 to be welded are changed, seam welding can be performed without causing defective welding.
UMEDA TSUNAHARU
SAHASHI KENJI
NA DETSUKUSU KK