Method of electrical resistance spot welding
First Claim
1. A method of welding comprising:
- contacting a metal sheet with at least one electrode having a first contact surface area at a force to provide a pressure to a contact surface of the metal sheet, wherein the first contact surface area has a starting position displaced from the contact surface by a stroke dimension, wherein the stroke dimension is equal to a difference in the starting position and a position of the electrode tip when the electrode tip makes contact to the contact surface of the metal sheet;
applying a current through the at least one electrode to the metal sheet;
measuring a dimensional change of the stroke dimension;
correlating the dimensional change in the stroke dimension to the change in the first contact surface area of the at least one electrode using a mathematical algorithm,
D2 to D1 area ratio=0.0977(Δ
X2)+0.625(Δ
X)+1.0wherein D1 is equal to a first diameter of an electrode tip of the at least one electrode, D2 is equal to a second diameter of the electrode tip of the at least one electrode, Δ
X is equal to the dimensional chance of the stroke dimension, and the at least one electrode has a 45 degree truncated electrode tip geometry; and
adjusting the force to compensate for the dimensional change in the first contact surface area of the at least one electrode to maintain the pressure applied to the contact surface of the metal sheet.
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Accused Products
Abstract
A method of resistance welding comprising the steps of contacting a metal sheet with an electrode having an initial contact surface area at a force to provide a pressure to the metal sheet applying a current through the electrode to the metal sheet; measuring dimensional changes of the electrode; correlating dimensional changes in the electrode to changes in the initial contact surface area; and adjusting the force to compensate for the changes in the initial contact surface area of the electrode to maintain pressure to the metal sheet. The force may be adjusted by stepping the force to maintain pressure to the faying surface of the metal sheet to be welded. By maintaining the pressure at the faying surface the life cycle of the electrodes may be increased without forming discrepant welds. The current may also be stepped to further extend electrode life.
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Citations
22 Claims
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1. A method of welding comprising:
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contacting a metal sheet with at least one electrode having a first contact surface area at a force to provide a pressure to a contact surface of the metal sheet, wherein the first contact surface area has a starting position displaced from the contact surface by a stroke dimension, wherein the stroke dimension is equal to a difference in the starting position and a position of the electrode tip when the electrode tip makes contact to the contact surface of the metal sheet; applying a current through the at least one electrode to the metal sheet; measuring a dimensional change of the stroke dimension; correlating the dimensional change in the stroke dimension to the change in the first contact surface area of the at least one electrode using a mathematical algorithm,
D2 to D1 area ratio=0.0977(Δ
X2)+0.625(Δ
X)+1.0wherein D1 is equal to a first diameter of an electrode tip of the at least one electrode, D2 is equal to a second diameter of the electrode tip of the at least one electrode, Δ
X is equal to the dimensional chance of the stroke dimension, and the at least one electrode has a 45 degree truncated electrode tip geometry; andadjusting the force to compensate for the dimensional change in the first contact surface area of the at least one electrode to maintain the pressure applied to the contact surface of the metal sheet. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A method of electrical resistance welding a metal sheet having a thickness and an alloy composition, the method comprising the steps of:
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a. determining a contact surface area of at least one electrode; b. determining a contract pressure based on (i) the contact surface area, (ii) the thickness, and (iii) the alloy composition; c. determining a current and a mechanical force to apply the contact pressure to the metal sheet; d. advancing the least one electrode from a starting position toward the metal sheet until the at least one electrode contacts the metal sheet such that the mechanical force is substantially applied to the metal sheet; e. applying the current through the at least one electrode to the metal sheet and terminating the current at the completion of a weld cycle; f. retracting the at least one electrode to the starting position; g. advancing the at least one electrode from the starting position toward the metal sheet until the at least one electrode contacts the metal sheet; h. measuring a difference in a stroke dimension; i. calculating a change in the contact surface area of the at least one electrode using a mathematical algorithm comprising;
D2 to D1 area ratio=0.0977(Δ
X2)+0.625(Δ
X)+1.0wherein D1 is equal to a first diameter of an electrode tip of the at least one electrode, D2 is equal to a second diameter of the electrode tip of the at least one electrode, Δ
X is equal to the dimensional chance of the stroke dimension, and the at least one electrode has a 45 degree truncated electrode tip geometry; andk. repeating steps c-i for subsequent weld cycles as required until the completion of the metal sheet welding, whereby either the current or the mechanical force or combinations thereof can be incrementally stepped between weld cycles to compensate for the decrease in the contact pressure that results from the increase contact surface area as the at least one electrode erodes during the weld cycle. - View Dependent Claims (21, 22)
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Specification