Q & A: What is Capacitive Discharge Stud welding?

There are basically two forms of stud welding.  One is drawn arc stud welding, which is the better known process.  The other is Capacitive Discharge (CD) stud welding.

In traditional drawn arc stud welding, the energy for the weld is generated as it is being consumed by the weld.  The electronics in a drawn arc welder can generate power for extended periods of time (seconds).  However, in CD welding, the system uses stored energy to generate the welding power.  It is this stored energy, in combination with the weld stud tip design, which achieves good stud welds.

Capacitive Discharge (CD) stud welds, final product by Image Industries

Final weld product for Capacitive Discharge (CD) stud welding process.

CD welders store energy in electronic components known as capacitors (hence “capacitor discharge”).  These components can store large amounts of energy in a relatively small space.  The electronics in the system charge the capacitors up to a preset voltage.  This pre-set voltage is set by the user, and varies depending on the fastener size.

When the CD weld cycle is initiated, the electronics unleash all the stored energy contained in the capacitors.  All that energy flows through the weld stud and through the ignition tip.  Like a fuse, the tip is purposely too small to handle the significant rush of electrical current.  The weld tip vaporizes allowing the formation of an arc.  This arc formed between the stud and the base material melts the surface of both parts.

The mechanical components in the CD system drive the fastener towards the base material.  During this driving toward the base material time the arc is maintained by the continuing discharge of the capacitors.  The arc is extinguished when the stud comes into contact with the base material.  The molten material solidifies and the weld is complete!

This all happens in a time range of .006 to .012 seconds.  That is faster than the blink of an eye!

Image Industries offers all pieces of the puzzle for your next capacitive discharge welding project, including all types of CD studs. Visit the Image Industries website today to view our selection of CD weld studs and CD welding equipment. Other questions about CD welding? Contact us here.