Direct and indirect spot welding
In today’s issue, we take a look at the topic of direct and indirect spot welding. In normal, commonly used spot welding, two welding electrodes are positioned on the opposite sides of the workpieces. In this case, the welding current can flow directly through the area to be welded.
This is why we speak of direct welding or also two-sided welding. As a rule, one welding lens is produced per welding process. Most standard machines and welding guns are built for this variant. If several spots are to be welded, this can be achieved with a special variant of two-sided welding, also with only one power source. In this case, several electrodes can be welded simultaneously. Care must be taken to ensure equal forces, as well as equal current and resistance distribution, so that all points welded at the same time also achieve identical results.
In many situations, it is impossible to position the electrodes on opposite sides of the workpiece. Then indirect or one-sided welding is used by feeding the electrodes from one side only. On the opposite side, a lower copper is usually held against it. An example of this is very large assemblies such as automotive floor assemblies, which require very expansive machines for indirect welding. Another example is points in the viewing area (A-pillar). The lower copper of the opposite side is used to avoid the dot impression of the electrode. In indirect welding, at least two welding spots are usually created per welding process.
By using contact electrodes, however, single spot welding can also be realised.