What is the principle of ultrasonic plastic welding

The principle of ultrasonic welding is to convert a 50/60 Hz current into 15KHz or 20KHZ electric energy from a 220V power supply through an ultrasonic generator. The converted high-frequency electric energy makes the output power of the high-frequency inverter circuit meet the rated power required by the transducer. The transducer is converted into mechanical motion of the same frequency, and then the mechanical motion is transmitted to the welding head through a set of horn devices that can change the amplitude. The welding head transfers the received vibration energy to the joint of the workpiece to be welded. In this area, the vibration energy is converted into heat energy by friction to melt the plastic. After the ultrasonic stops, let the pressure continue for a few seconds to make it solidify and shape, so that a strong molecular chain is formed to achieve the purpose of welding, and the welding strength can be close to the strength of the raw material. The quality of ultrasonic plastic welding depends on three factors: the amplitude of the transducer's welding head, the applied pressure and the welding time. The welding time and welding head pressure can be adjusted, and the amplitude is determined by the transducer and the horn. There is a suitable value for the interaction of these three quantities. When the energy exceeds the suitable value, the melting amount of the plastic is large, and the welded material is easy to deform; if the energy is small, it is not easy to weld firmly, and the applied pressure cannot be too large.