Capacitor Discharge (CD) Stud Welding is also a semi-automatic arc welding process. However, with CD welding small diameter fasteners (1/4" and under) are end welded to extremely thin gauge parent metal. The CD process operates on the principle of capacitor stored energy which is instantaneously discharged by the equipment system through a special weld "timing" tip. Since the entire weld cycle is completed in several milliseconds, welds can be made to thin sheet without pronounced distortion, burn-through or discoloration. CD welding permits stud welding of dissimilar metals.