Coils with multiple termination points can be welded at one automation station. Article by James Tod, Amada Miyachi UK.
Pulse micro arc welding is a good choice for coil termination applications, especially as coils are getting smaller and smaller. Other processes do not lend themselves as well for these applications. For example, it can be difficult for lasers to target the pins, while resistance welding is not practical due to electrode size, and soldering involves potentially hazardous fluxes. Multiple output pulsed arc welders are available that offer great automation layout flexibility and increase production line throughput.
Pulse Micro Arc Welding Basics
Pulse micro arc welding is a zero-contact process in which an electrical arc is struck between an electrode and target component. The arc generates very high and concentrated energy density, which results in high local temperatures that can be used for welding. Sophisticated closed loop power supplies are used to establish and maintain the arc under precisely controlled electrical conditions.
The micro arc coil termination process requires wire to be wound onto the pin in a uniform fashion and density. The welding process is accomplished by heating the pin and encapsulating the wire in the molten pin material. The wound pin is positioned close to a welding electrode and an arc struck between the pin and the electrode.
Operators profile the energy and current within the arc in terms of rate of rise, period of peak, and downward cooling to control the rate at which the pin begins to melt back. The process of melting the pin back creates a molten ball that causes the wire and its insulation to melt simultaneously, thus welding the wire to the pin.
Material Type is Critical to the Process
With micro arc welding, the materials must flow together based on the heat generated by the welding arc and the surface tension of the materials. Any contamination can cause the materials to fail to fuse with one another.
Wire insulation is critical because it must be broken down by the heat in the weld before the materials can fuse with one another. In the process, the pin is heated directly and the wire indirectly; if the wire insulation remains intact during the weld, the pin will be melted but the wire will not. Pulsed micro arc termination welding works best with wire insulation rated for temperatures of 180 deg C or lower.
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