Differences Between CD and Arc Systems

What Process Should You Use?

Capacitor Discharge stud welding is a semi-automatic arc welding process. However, with CD welding, you have the ability to weld small diameter studs to very thin material. Since the entire weld cycle is completed in several milliseconds, welds can be made to thin sheets of metal without pronounced distortion, burn through or discoloration. The CD process allows stud welding of dissimilar metals.

The CD process is commonly used in most sheet metal shops.

Arc stud welding allows almost any size or type of weld stud to be welded. Studs must be manufactured from weldable material and designed with a special arc stud tip. With the Arc process, you obtain a full fusion weld that becomes stronger than the stud itself. Arc stud welding is applicable to mild steel, stainless steel and aluminum.

The Arc process is commonly used in most fabricating/structural steel shops.

Capacitive Discharge

CD Fasteners generally utilize a specially engineered projection or tip at the weld base. It’s design configuration and length provide accurate welding time control, for consistently reproducible results.
Instantaneous energy is discharged from banks of low voltage DC electrostatic capacitors, electronically controlled and triggered on demand by the operator.
Actuating the triggering circuit releases the stored energy from the capacitors through the stud, vaporizing the high resistance tip and creating an ionization path for peak current flow and arcing across the areas to be joined.
Spring or air pressure of the gun upon the partially melted stud fuses it to the parent metal surface, completing the weld in four to six milliseconds and creating a bond stronger than the fastener itself.


The Stud Fastener held in the weld gun is applied firmly to the work surface under spring tension. Arc welding derives its source of energy from either DC rectifiers or motor-generator set. Its degree and intensity are automatically controlled by precision timing circuits.
The trigger button initiates the cycle which energizes the gun solenoid, lifting the stud from the metal surface and creating an arc which melts a flux-loaded end of the fastener and its immediate area.
A ceramic ferrule shields the arc, concentrates the heat and contains the molten metal in the weld zone. Simultaneously, the gun solenoid becomes de-energized and the spring tension forces the fastener into the molten pool, integrating it with the parent metal.
The cycle is completed in less than a second and the resulting weld bond develops the full strength of the fastener in the weld zone. The expendable ferrule is broken away to expose a smooth and complete fillet at the stud base.

Length Information

Capacitor Weld Pins are available in 12-GA and 14-GA up to lengths of 6-inches as standard. Special lengths are available upon request.

Capacitor Weld Studs are manufactured in minimum lengths of 1/4-inch up to 2-inch as standard. Other lengths are available upon request.

Capacitor Weld Studs and Pins do not undergo any loss of length after welding.

Arc Studs are available from minimum lengths After Weld (AW) shown on individual specification sheets up to any length in increments of 1/8-inch. Please call one of our service representatives for specification sheets.

All Arc Studs and Pins are reduced approximately 1/8-inch in length after welding for diameters up to 1/2-inch weld base diameter and approximately 3/16-inch for 5/8-inch weld base or larger.