The working principle of the ultrasonic welding machine requires that the two parts to be combined, one on top vibrates and the other on the bottom is stationary. The friction heat on the contact surface melts the plastic on the surface and combines.

The ultrasonic energy is transmitted to the welding area through the upper weldment. Since the acoustic resistance of the welding area, i.e. the interface between the two welds, is large, local high temperature will be generated. Because the thermal conductivity of plastic is poor, it cannot be dissipated in time for a while, and it gathers in the welding area, causing the contact surface of the two plastics to melt rapidly. After a certain amount of pressure is applied, it is fused into one. When the ultrasonic wave stops working, the pressure is continued for a while, and it is solidified and formed. In this way, a strong molecular chain is formed to achieve the purpose of welding. The welding strength can be close to the strength of the raw material itself.