In the Capacitor Discharge Process, the capacitors are charged to a pre-set voltage to suit the diameter of stud to be welded.

Upon triggering, the stored energy is discharged as a high current pulse melting the pip & producing
an arc.

Return spring pressure forces
the stud into the molten surface area to give complete fusion across the flange.

Optimum welding takes place when the molten metal reaches the edge of the flange as the stud meets the work piece.