Resistance Welding Configurations

Resistance Welding Configurations

Resistance welding process provides a variety of alternatives for weld configurations (or geometry). The one most commonly used is the opposed electrode configuration where the two electrodes are on opposite side of the weld and are able to pinch the parts between the electrode tips. The opposed configuration is one of the most robust since the electrodes also act to force the parts together and are least likely to provide alternate paths to current flow. In situations where the other side of the part is not easily accessible, as would be the case when welding a tab to the battery can, the parallel gap welding configuration can be used. As can be seen from the schematic, the two electrodes (orange in color) approach the weld assembly from the same side and come in contact with only one of the parts being welding, typically the weld tab on top. As the current flows from one electrode to the other, it passes through the weld assembly. Based on the welding force, thickness of the tabs, and the gap between the electrodes, the welding current can be coaxed to flow across the welding interface and form a bond. If the electrode separation is sufficient, two weld nuggets can be made. Typically, the electrodes are quite close and a single weld spot forms at the interface. In situations where the tab on top is very conductive or is very small, one of the electrodes will have to be placed on the lower part, as is shown in the step welding configuration. Step welding forces the current to flow through the weld interface and hence is more robust. In some welding applications, one of the parts is much bigger than the other and it becomes very difficult to simultaneously heat both parts. To solve the problem, a projection is made on the bigger of the two parts; the projection can be machined, stamped, or coined. The projection helps both parts to get heated simultaneously and form a strong bond.