Ultrasonic plastic welding (USW) is the joining or reforming of thermoplastics through the use of heat generated from high-frequency mechanical motion. It is accomplished by converting high-frequency electrical energy into high-frequency mechanical motion.

In ultrasonic plastic welding, a vibratory motion at the horn face (amplitude) is transferred to the part. The vibrations move through the part and creates friction at the interface between the parts. Creating heat, then melting. When cooled, a weld is formed.

Ultrasonic welding is a method of joining thermoplastic components by heating and subsequent melting of surfaces in contact. Mechanical vibration with frequency between 10 and 70 kHz and amplitude of 10 to 250 μm is applied to joining parts.

Ultrasonic welding (USW) involves converting high-frequency electrical energy into high-frequency mechanical motion, which, along with applied force, creates frictional heat at the plastic components' mating surfaces. This heat causes plastic material to melt, forming a molecular bond between the parts.

The process of ultrasonic welding of plastics is achieved by applying a vibrating metal tool (horn) at 90° to the stationery plastic parts which then vibrate. When combined with pressure, friction produces heat & melts the parts at the horn contact point. Once cooled down a solid homogeneous weld between the 2 parts is created.