The most widely used technique for welding is arc welding. It functions by striking an electric arc between an electrode, and the object being welded. The object itself is part of the electric circuit needed for the device to operate properly. In less common welders, two electrodes may be used. The voltages generated by the electrode and the object are always too low to cause any danger (usually 20 to 100 volts maximum). The varying voltage is dependent on the conditions being worked in and the type of material being welded.
The principle of arc welding is very simple, the supply voltage is converted to a low voltage, high current, supply by a large transformer in the welder. The positive connection to this transformer is fed via a flexible lead to a hand held welding rod. The negative connection is fed to a large crocodile clip or clamp which is clamped to the metal object to be welded. When the positive welding electrode is placed on the metal object, a short circuit is caused, an arc is struck, a high current passes and the metal melts and fuses.
The technique of arc welding is more rapid than gas welding. It is also extremely adaptable, as it is well suited to fully automatic operations, as in robot welders for the manufacture of motor vehicles.
