Resistance welding is a thermo-electric process in which heat is generated at the interface of the parts to be joined by passing an electrical current through the parts for a precisely controlled time and under a controlled pressure (force). The name “resistance” welding derives from the fact that the resistance of the workpieces and electrodes are used in combination or contrast to generate heat at their interface.
While Amada Miyachi America not invent resistance welding, it perfected the technology and was the first to apply it to welding small microelectronic modules in the early 1950’s. Today, Amada Miyachi offers a wide range of welding technologies which have been used successfully for decades. Core resistance welding technologies include Linear DC, High Frequency Inverter, Capacitive Discharge and AC. They are used for resistance spot welding, seam welding, gap welding, projection welding, thermo compression bonding, strand welding and insulated wire welding.
The physical metallurgy of the materials to be welded determines the application of the resistance welding process variables. In general there are two categories of metals to be welded: “Conductive” (such as aluminum, copper, silver and gold), and “Resistive” (steel, nickel, Inconel, titanium, tungsten, molybdenum) with a third, small, middle ground category occupied primarily by brass. In general, electrically conductive materials are also more thermally conductive and are softer. To determine whether your materials are suitable for resistance welding, please refer to our Material Weldability App at http://www.amadamiyachi.com/educationalresources/weldability.
Energy is supplied by a welder with either an internal or external transformer which both powers and controls the application of heat and time in the resistance welding process. In general terms, resistance welding applies high current with low voltage. In simple terms the resistance welding power supply transforms, modulates and controls the electrical energy of the power line and applies it to the weld according to a user defined or user programmed “weld schedule.” Depending on the complexity and intricacy of the power supply the user can program from one to more than 100 attributes and permutations of the welding process, and, using a microprocessor, store these attributes as a uniquely defined “weld schedule.” Amada Miyachi America offers a full range of resistance spot welders with 5 – 200,000 A output power including high frequency inverter, linear DC, capacitive discharge and AC technologies capable of addressing both small and large welding applications.
A key parameter of all three types of resistance welding is weld pressure or force. The proper and consistent application of force improves the mating of the materials increasing the current paths, reducing the interface resistance, and insuring that any oxide barriers between the workpieces are broken through. Repeatable force control insures repeatable weld quality through consistent electrical contact resistance and consistent heat balance. Force control can also be used to trigger welding energy when a pre-determined force level has been achieved, often called “force firing.” Optimum welds are achieved when the applied force is precise, repeatable, controlled by time schedule, used to fire the power supply, and regulated both to reduce the initial impact and not to become excessive after the weld.
Amada Miyachi offers a full range of resistance welding heads including manual, air-actuated, and electromagnetic models with opposed, step, series, and parallel gap electrode configurations. Force ranges from just .39lbs to 1800lbs to address both fine and large scale spot welding applications.
Real time weld monitors - also called weld checkers - are invaluable tools for production monitoring, process development and weld quality analysis. Weld monitors measure one or more of the electrical and/or mechanical parameters that dynamically change during the welding process including weld current, voltage drop across the electrodes, workpiece expansion and deformation, electrode force, electrode displacement (movement) and more. Amada Miyachi offers a full range of desktop, hand-held and machine-mountable weld monitors / weld checkers, some with built-in printers or RS232 output.
Finally – Amada Miyachi also offers a full selection of resistance welding accessories to enhance and improve your results and provide additional safety. These accessories can be broken down into a few basic but important categories: resistance welding handpieces, process observation and verification accessories like microscopes and pull testers, fume extraction, water chillers, footswitches, force gauges, electrodes and more.