Applications

Resistance Welding

Resistance welding involves several steps that are coordinated with each other. First, the workpieces are fixed in place with clamps to ensure a stable position of the joint. This is followed by welding, in which electrical energy is directed through the workpieces via electrodes over defined areas to create the welded joint. After the welding phase, the pressure is held briefly to ensure an optimum connection before the clamps are opened.

The process principle of resistance spot welding is based on the use of electrically conductive base materials, which are joined together by a welding energy source, usually in the form of high current at low voltage. Electrode holders hold the electrodes, which transfer the current to the workpieces. Water cooling ensures that the electrodes do not overheat. The contact pressure is crucial to minimize the contact resistance and ensure an effective welded joint. Welding lenses are created between the sheets where the resistance is greatest. To control this, voltage and current are measured and resistance and power are calculated in order to improve the welding quality through control in ms cycles and to monitor quality.
Resistance projection welding uses a similar principle, but with special welding electrodes to establish contact with workpieces, which then achieve defined contact resistances at the points to be joined via embossed projections. The contact pressure is important in order to deform the welding projections in a targeted manner and create a stable joint with a high fusion depth.

The resistance ratios in spot and projection welding are always made up of the contact resistance and the material resistance. A simplified electrical equivalent circuit diagram shows that the electrical power at the welding point can be calculated using the formula P = U_R * I. The electric current always takes the path of least resistance, and the resistance increases as the temperature rises, which supports the process.