METHOD FOR DISCRIMINATING QUALITY OF PROJECTION WELDING

PROBLEM TO BE SOLVED: To provide a method for automatically determining whether the quality of welding is satisfactory or not in projection welding. SOLUTION: A nugget is formed in projection welding by pressurizing and energizing, with a pair of electrodes 1a, 1b, a to-be-welded material 2 having a projection and a to-be-welded material 2 not having a projection. In a method for discriminating the quality of the projection welding, test welding to form a proper nugget is conducted prior to the regular welding. Time variations of an instantaneous power value Pd during the test welding are A/D converted at a predetermined period and stored as a data string. A power reference-value generating circuit PS generates a power reference pattern based on the stored data file, and, when the instantaneous power value Pd during the regular welding varies within the predetermined range Ps±ΔPs from the power reference pattern, the quality of welding is discriminated to be satisfactory. COPYRIGHT: (C)2011,JPO&INPIT