| 摘要 |
PROBLEM TO BE SOLVED: To perform the welding in an arc stud welding by detecting stains on the surface of a work piece, and sufficiently cleaning the surface. SOLUTION: When the main current I is fed by the start signal to energize the electric arc, the voltage U of the arc (or its means voltage Uavg ) is measured with the intervalsΔtm . When the measured voltage U is much larger than the threshold voltage Us , the surface stain is judged to be present, and the stain is cleaned by superposing the positive purifying pulse on the main current I. Measurement of the voltage U and feeding of the purifying pulse are repeated, and the stain is judged to be eliminated when the voltage U is not more than the threshold voltage Us . The main current I is increased and kept, and the actual welding process is performed. The number of repetition may be limited by the feeding number of the purifying pulse.
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