PURPOSE: To prevent the contamination of a slag, and to improve the yield of a formed part by detecting a reignition voltage of an AC electrode and classifying it to plural classes, and controlling the inter-electrode distance so that its standard deviation becomes below a prescribed value based on a result of the classification.
CONSTITUTION: In case of a two electrode arc welding, a relation of an inter- electrode distance (horizontal axis) and a standard deviation V (vertical axis) of a reignition voltage becomes as shown by a graph. That is to say, the standard deviation V of the reignition voltage can be adjusted to a desired small value by adjusting suitably the inter-electrode distance (horizontal axis). Therefore, the inter-electrode distance so that its standard deviation V becomes below a prescribed value based on a result of a classification, by detecting the reignition voltasge of the AC electrode and classifying it to plural classes. Accordingly, the standard deviation V is maintained at a desired small value.
KAWAI KAZUO
ADACHI SEIZO
ASHIHARA MAKOTO
