Patent ID: 7718918

Claim:
A production line method of spot welding comprising the steps of: a. providing a pair of electrodes, wherein an electrode of the pair of electrodes comprises a tip, a tip surface area, a length, and a plurality of diameters along the length, wherein the electrode tip surface area is substantially proportional to a diameter of the plurality of diameters relative to the electrode length as the electrode tip erodes; b. determining a pressure and a current for a weld cycle of a welding operation; c. developing a relationship between an electrode force with the electrode length as the electrode tip erodes to substantially maintain the pressure for the weld cycle; d. contacting a metal sheet with the electrode; e. applying the electrode force associated with the length of the electrode to provide the predetermined pressure to the metal sheet; f. measuring a stroke dimension of the electrode, wherein the stroke dimension is a distance from a reference point of the electrode to a contact surface of the metal sheet prior to applying the electrode current; g. applying the electrode current through the electrode to the metal sheet to generate a weld, a new tip surface area of the electrode, a new electrode length, and a new contact surface of the metal sheet; h. measuring a new stroke dimension, wherein the new stroke dimension is a distance from the reference point of the electrode to the new contact surface of the metal sheet; i. determining the new electrode length, wherein the new electrode length equals the electrode length less the difference of the new stroke dimension and the stroke dimension; and j. repeating steps d-i to substantially maintain the pressure for subsequent weld cycles until completion of the welding operation without increasing the current, whereby, the electrode force is adjusted for each weld cycle to compensate for the change in the electrode tip surface area as the electrode erodes.