The process “stud welding with tip ignition” is used for studs up to a diameter of approximately 8 mm. Studs, having a small cylindric tip, are in use. A capacitor battery serves as power source. The maximum current can reach 10.000 A; the welding time is between 1 and 3 ms.
The capacitor battery will be loaded up to a defined voltage. In general, the negative pole will be connected to the stud. The studs with its precisely dimensioned cylindric tip will be moved to the workpiece. With the contact of the tip to the workpiece, the circuit closes. The quickly increasing current is melting the welding tip and with it, the arc will ignite. Stud and workpiece are melting. By the contact between stud and workpiece, the arc will lapse, the melting zones join tightly and solidify. The remaining energy of the capacitor will unload by a short-circuit.
Stud welding with tip ignition comprises two different processes.
As discribed above, in the course of the process “welding with gap” the stud will be accelerated to a certain speed. The movement will not be delayed by the ignition process.
In the course of the process “welding with contact”, spring force will move the stud to the workpiece. Caused by the increasing current, the welding tip will melt promptly and ignite the arc. Now the stud moves towards the workpiece and melts. As the stud must be accelerated from static condition, the result is a longer welding time, compared to the process “welding with gap”.
The extremely short welding process can only be followed by the aid of oscillograph curves. The measuring instruments, which are nowadays availble, are capable to store the process and thus allow an exact evaluation of the cycle.
