Resistance projection welding system and method for welding a projection weld nut to a workpiece

A resistance projection welding system for welding a projection weld nut having a first surface provided with a pilot ring and a second surface to a workpiece only if said pilot ring abuts and is properly aligned to said workpiece, said welding system comprising:

• a weld power source for supplying power;
• a weld gun having a welding electrode coupled to said weld power source, said welding electrode being moveable between a closed welding position for electrical welding contact between said projection weld nut and said workpiece, and an opened position for receiving and removing said projection weld nut and said workpiece;
• a displacement sensor coupled to said weld gun for generating a signal responsive to an orientation of said welding electrode relative to said workpiece;
• and
• a computer coupled to said weld power source and to said displacement sensor, said computer processes said displacement sensor signal to monitor said orientation of said welding electrode relative to said workpiece, said computer transmits a control signal to said weld power source to inhibit the application of power from said weld power source to said welding electrode if said first surface with said pilot ring of said projection weld nut engages said welding electrode and to initiate the application of power from said weld power source to said welding electrode if said second surface of said projection weld nut engages said welding electrode.

A resistance projection welding system for welding a desired surface of a projection weld nut having a first and a second dissimilar surface to a workpiece, said welding system comprising:

• a weld controller having a first and a second output terminal for providing electrical power;
• a weld gun having a first and a second electrode, said first electrode engaging said projection weld nut and being electrically coupled to said first output terminal of said weld controller, said second electrode engaging said workpiece and being electrically coupled to said second output terminal of said weld controller, said first electrode and said second electrode being moveable relative to each other between a closed welding position forming electrical welding contact through said projection weld nut and said workpiece, and an opened position for receiving and removing said projection weld nut and said workpiece;
• a displacement sensor coupled to said weld gun for generating a displacement sensor signal proportional to an orientation of said first electrode relative to said second electrode;
• and
• a computer coupled to said weld controller and to said displacement sensor, wherein said computer processes said displacement sensor signal to determine which surface of said projection weld nut engages said workpiece, said computer transmits a control signal to said weld controller for initiating an application of electrical power from said weld controller to said electrodes if said first surface of said projection weld nut engages said workpiece and for inhibiting said application of electrical power from said weld controller to said electrodes if said second surface of said projection weld nut engages said workpiece.

A method for welding a projection weld nut to a workpiece utilizing a weld controller, a computer, a projection weld nut feeder, and a weld gun having a welding electrode being moveable between a closed welding position for electrical contact between said projection weld nut and said workpiece, and an opened position for receiving and removing said projection weld nut and said workpiece, wherein said projection weld nut has a first face and a second face, said welding method comprising the steps of:

• positioning said projection weld nut and said workpiece within said welding electrode of said weld gun when said welding electrode is in said opened position by utilizing said projection weld nut feeder;
• shifting said welding electrode to said closed position in response to a first instruction from said computer thereby forming an electrical contact between said projection weld nut and said workpiece;
• generating a signal responsive to an orientation of said welding electrode relative to said workpiece by utilizing a displacement sensor;
• determining which face of said projection weld nut engages said workpiece by utilizing a computer responsive to said displacement sensor;
• transmitting a signal from said computer to said weld controller for initiating an application of electrical power from said weld controller to said welding electrode if said first face of said projection weld nut engages said workpiece and for inhibiting an application of electrical power from said weld controller to said welding electrode if said second face of said projection weld nut engages said workpiece;
• and
• shifting said welding electrode to said opened position in response to a second instruction from said computer for receiving and removing said projection weld nut from said welding electrode.