A spot welding process using series-opposed split transformers. It consists of a dual point moving electrode welding unit and a dual point backup unit with flat electrodes. Advantages of this type of equipment are that spot welds are produced with flat surfaces, without indentations, on the side of the joint against the flat backup electrodes. This is particularly desirable for spot welding sheet metal cabinets, furniture and boxes.
Mounting flexibility is achieved when the backup unit is mounted in a fixed position with large flat electrodes, so that the moving unit may be moved to any position where the electrodes would make contact with the backup electrodes.