A very important factor in resistance welding technology besides the welding current, the welding time and the welding force is the current density. This is the ratio of the current flowing through a conductor to the conductor cross-section with the designation S, S = I/A in [A/mm2]. In spot welding, to put it simply, the ratio of welding current to electrode diameter. This current density is one of the factors determining the energy introduced into the weld. Consequently, one must not only compare or observe welding currents, but also the corresponding electrode area or diameter.
For this reason, the electrode diameters or types are always specified in the DVS leaflets or the welding machine manufacturers’ reference value tables.
At constant welding current, the electrode area determines the current density, which thus characterises the resistance of the weld. Consequently, the current density in the welding area becomes smaller and smaller if the electrode area becomes larger due to wear at a constant current. This is also the reason for programming the stepper function, which counteracts the increase in electrode area and thus the decreasing current density by increasing the welding current.