Advanced Process (AP) weld studs are so named because they can be used with a variety of stud welding processes. These processes include: drawn arc (typically short arc), capacitor discharge (drawn arc style CD), gas metal arc (also short gas metal arc). Since none of these processes use a flux load, typical weld penetrations are not as deep. Also, none of the AP processes typically require a ferrule. While this is an advantage from a material handling perspective, there is no fillet control. No fillet control means that the fillet can be somewhat random and unpredictable. This is particularly true when arc blow is a factor. Overall, this style of stud is economical and flexible and can fulfill the requirements of many applications.
Advanced Process Center Punch studs work similarly to AP studs and likewise work with a variety of processes. However, AP studs have a small projection on the weld face. This projection is used to help operators find center punch or witness marks. Typically, a turret press that punches out sheet metal can also leave center punch marks. The operator can then use the projection on the stud to find the center punch mark on the sheet metal.