Ultrasonic welding applies high-speed sound waves to two metal surfaces that are pressed together. The metals can be the same or dissimilar materials. Ultrasonic welding is used for repetitive small welds such as electronic parts and circuit boards. The control of the sound wave frequency and time of application control the welding process to prevent punching holes.
Arc welding uses electric current to generate the heat for welding. Many arc welders use a rod that melts into the two welded objects to become part of the weld. Arc welders control the voltage and amperage of the electric current to prevent damage or punched holes.
Gas torch welding uses a focused flame to heat the welded surfaces. Acetylene and propane fuels gas torches. Welders control the fuel flow and distance between the flame tip and the welded surface to prevent damage to thin metals. Some welding rods provide protection to thin metals in the welding process.
Welders use a noncontinuous process when welding thin metal. There is no continuous contact between the welding instrument and the welded surface. Welders melt a part of the metal then withdraw the welding instrument to allow the molten metal to cool then apply heat again to melt some more metal. This is repeated until completion. The welder's technique resembles a surgeon stitching shut an incision.