PROJECTION WELDING MACHINE

摘要

PROBLEM TO BE SOLVED: To accurately detect the setting state of a nut with an extremely simple structure and to prevent welding defects. SOLUTION: The upper electrode 15 is provided with a lower face 15d which has the outer diameter D1 slightly larger than that of the upper face 2d of a nut 2, and the lower face 15d is brought into contact with the entire upper face 2d of the directly facing nut 2. An electrically conductive collar 17 is mounted around the lower outer circumference of the upper electrode 15. The conductive collar 17 is provided with a lower face 17a which is almost flush with the lower face 15d of the upper electrode 15, and which is abutted on the plural parts 2b to be welded of the inverted nut 2. Insulating materials 16, 18 insulates electrically between the upper electrode 15 and the conductive collar 17. An abnormality detection controller energizes the conductive collar 17 and discriminates the set state of the nut 2 based on the presence/absence of the energization from the conductive collar 17 to the nut 2.