Ultrasonic welding principle: ultrasonic welding is the use of high frequency vibration wave to transmit to the surface of two objects to be welded, under the condition of pressure, the two objects surface friction between the formation of molecular layer fusion.
 
The main components of an ultrasonic welding system include: ultrasonic generator/transducer/horn/welding head triplet/die and frame. Ultrasonic welding is through the ultrasonic generator to 50/60Hz current into 15, 20, 30 or 40KHz electric energy. The converted high-frequency electrical energy is converted again through a transducer to a mechanical motion of the same frequency, which is then transmitted to the weld head through a set of amplitudes that can be changed. The welding head transfers the vibration energy received to the joint part of the workpiece to be welded, where the vibration energy is converted into heat energy by means of friction, melting the area of the part to be welded. Ultrasonic can not only be used to weld metals, hard thermoplastics, but also to process fabrics and films. This article mainly introduces two kinds of metal and plastic welding.
 
01 ultrasonic metal welding principle is the use of ultrasonic frequency (more than 16KHz) mechanical vibration energy, connecting the same metal or dissimilar metal a special method. In the process of ultrasonic welding, neither current nor high temperature heat source is applied to the workpiece, but the vibration energy of the frame is transformed into friction work, deformation energy and limited temperature rise between the workpiece under static pressure. Metallurgical bonding between joints is a solid state welding without melting of the base metal. Therefore, it can effectively overcome the splash and oxidation caused by resistance welding. Ultrasonic metal welder can weld single point, multi point and short strip of copper, silver, aluminum, nickel and other non-ferrous metal wire or thin sheet material. Can be widely used in thyristor lead, fuse piece, electrical lead, lithium battery pole piece, pole ear welding.
 
02. Principle of ultrasonic plastic welding
 
When the ultrasonic acts on the thermoplastic plastic contact surface, it will produce tens of thousands of times of high-frequency vibration per second. The high-frequency vibration reaching a certain amplitude will transfer the ultrasonic energy to the welding area through the upper weldment. Because the welding area is the junction of the two welding, the sound resistance is large, so it will produce local high temperature. And because of the poor thermal conductivity of plastic, it can not be distributed in time for a while, gathered in the welding area, resulting in the rapid melting of the contact surface of two plastics, plus a certain pressure, so that it is fused into one. When the ultrasonic wave stops, let the pressure continue for a few seconds to make it solidify, so as to form a strong molecular chain, to achieve the purpose of welding, welding strength can be close to the strength of the raw material.
 
The quality of ultrasonic plastic welding depends on the amplitude of the welding head of the transducer, the added pressure and welding time, the welding time and welding pressure can be adjusted, the amplitude is determined by the transducer and the horn. There is an appropriate value for the interaction of these three quantities. When the energy exceeds the appropriate value, the melting amount of plastic is large and the welding is easy to deform. If the energy is small, it is not easy to weld firmly, and the pressure added cannot be too large. The optimum pressure is the product of the length of the side of the welded part with the optimum pressure per 1mm of the edge.