A method of spot welding a workpiece stack-up that includes a steel workpiece and an aluminum alloy workpiece involves passing an electrical current through the workpieces and between welding electrodes that are constructed to affect the current density of the electrical current. The welding electrodes, more specifically, are constructed to render the density of the electrical current greater in the steel workpiece than in the aluminum alloy workpiece. This difference in current densities can be accomplished by passing, at least initially, the electrical current between a weld face of the welding electrode in contact with the steel workpiece and a perimeter region of a weld face of the welding electrode in contact with the aluminum alloy workpiece.

An apparatus and method for fastening layers of non-ferrous alloys, like aluminum, magnesium and copper utilizes a steel fastener and a spot welding machine. The fastener and metals are stacked and the heat from the welder's electric current softens the lower melting point aluminum allowing the fastener to penetrate the aluminum. A weld zone between the fastener and the various layers creates an internal weld. The fastener has a rough shaft that is coated by the molten weld zone and is hard to withdraw on solidification. Layers of non-conductive materials like plastics and ceramics may also be affixed to a conductive layer using a fastener made from a compatible material that extends through a pilot hole and welds to or penetrates a conductive layer. The fastener may have projections that initially reduce contact area with the stack.

A welding electrode for an electric resistance welding process. The welding electrode includes a body extending along a center axis and terminating axially at a weld face for contacting a work face. The weld face defines a center along the axis and defines an outer edge spaced radially from the center. A plurality of senates are defined along the weld face. Each of the serrates projects axially away from the weld face and extends radially from the center axis to the outer edge of the weld face. A higher density of the plurality of serrates is formed proximate to the center axis than proximate to the outer circumference of the weld face. Methods for using the welding electrode and forming the senates on the welding electrode are also provided.

A joining device for connecting a metal member and a resign member with a metal fastener including a penetrating tip comprises: a cylindrical nosepiece; a high frequency electromagnetic induction coil around the nosepiece; an electrode punch for pressing the fastener into the resign member; a electronic chopper for producing a high frequency current; a high frequency power supply for supplying an induction current to the induction coil; a welding power supply for supplying a welding current between the electrode punch and the metal member; a contact detector for sensing when the fastener tip touches the metal member; and a switching unit for automatically switching from the induction current to the welding current when the contact detector senses that the tip has contacted the metal member.

The invention relates to an apparatus and a method for the low-resistance welding of metal sheets with a high cycle rate.

A welding gun includes first and second movable arms, and first and second welding electrodes. The first and second movable arms are movable upward and downward. The first and second welding electrode are disposed respectively on the first and second movable arms. The welding gun is capable of performing a first mode in which the first and second welding electrodes are brought into contact with one side of a workpiece to weld the workpiece, and a second mode in which the workpiece is sandwiched by the first and second welding electrodes to weld the workpiece. The first and second welding electrodes are pivotally supported by the first and second movable arms, respectively. Each of the first and second welding electrodes has a rotatable roller shape. The first movable arm includes a first slide mechanism configured to allow the first welding electrodes to slide to below the second welding electrode.

A method of spot welding a workpiece stack-up that includes a steel workpiece and an aluminum alloy workpiece involves passing an electrical current through the workpieces and between welding electrodes that are constructed to affect the current density of the electrical current. The welding electrodes, more specifically, are constructed to render the density of the electrical current greater in the steel workpiece than in the aluminum alloy workpiece. This difference in current densities can be accomplished by passing, at least initially, the electrical current between a weld face of the welding electrode in contact with the steel workpiece and a perimeter region of a weld face of the welding electrode in contact with the aluminum alloy workpiece.

A spot welding system includes a spot welding gun, a robot, and a tip dresser that polishes a face of electrode. The tip dresser includes a blade that cuts the face of the electrode and a blade driving motor that rotates the blade. A dresser control section of a control device detects torque of the blade driving motor. When the torque of the blade driving motor exceeds a predetermined torque upper limit value, the dresser control section carries out speed reduction control that reduces the rotation speed of the blade driving motor.

A spot welding system 10 includes a spot welding gun having an opposite electrode 44, a movable electrode 48, and a drive part 52, a position detection part 54 that detects a position of the movable electrode 48, and a pressure change calculation part that calculates an amount of change between first pressurizing force at a first attitude and second pressurizing force at a second attitude based on a first position of the movable electrode 48 when the drive part 52 has been driven by a first pressurizing force command at the first attitude, a second position of the movable electrode 48 when the drive part 52 has been driven by the first pressurizing force command at the second attitude, and the first pressurizing force command. The first pressurizing force command and the first pressurizing force coincide with each other.

A method of resistance spot welding a steel workpiece and an aluminum or aluminum alloy workpiece together includes several steps. In one step a workpiece stack-up is provided. The workpiece stack-up includes a steel workpiece and an aluminum or aluminum alloy workpiece. Another step involves providing a first welding electrode that confronts the aluminum workpiece, and providing a second welding electrode that confronts the steel workpiece. The first welding electrode has an electrode body and an insert that functions to limit or eliminate heat flux into the electrode body. Other steps of the method involve bringing the first and second welding electrodes into contact with opposite sides of the workpiece stack-up and resistance spot welding the stack-up.