When the ultrasonic effect on the thermoplastic plastic contact surface, will produce tens of thousands of times per second of high-frequency vibration, this high-frequency vibration reaches a certain amplitude, through the upper weldment ultrasonic energy transmission to the weld zone, due to the weld zone that is the two welding interface acoustic resistance, and therefore will produce a localized high temperature. And because of the poor thermal conductivity of plastic, a moment can not be distributed in a timely manner, gathered in the weld area, resulting in the contact surface of the two plastics quickly melted, plus a certain pressure, so that it fused into one. When the ultrasonic stop acting, let the pressure continue for a few seconds, so that it solidified molding, so that the formation of a solid molecular chain, to achieve the purpose of welding, welding strength can be close to the strength of the raw material. Ultrasonic plastic welding is good or bad depending on the amplitude of the transducer welding head, the pressure and welding time and other three factors, welding time and welding head pressure can be adjusted, the amplitude of the transducer and the amplitude of the rod decision. These three quantities interact with a suitable value, energy more than the appropriate value, the amount of plastic melting is large, the weld is easy to deform; if the energy is small, it is not easy to weld, the pressure added can not be too large. This optimal pressure is the length of the welded part of the edge and the edge of the optimal pressure per 1mm of the product