Increase knowledge: understand the principle of ultrasonic welding in a penny second

Ultrasonic welding uses high-frequency vibration waves to be transmitted to the surfaces of two objects to be welded. Under pressure, the surfaces of the two objects are rubbed against each other to form a fusion between molecular layers.

Ultrasonic welding uses an ultrasonic generator to convert 50/60 Hz current into 15, 20, 30 or 40 KHz electrical energy. The converted high-frequency electric energy is again converted into mechanical motion of the same frequency through the transducer, 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, which melts the area of the part that needs to be welded. Ultrasonic waves can be used not only to weld metals and hard thermoplastics, but also to process fabrics and films. This article mainly introduces two kinds of metal and plastic welding.

1) Principle of ultrasonic metal welding

The principle of ultrasonic metal welding is to use the mechanical vibration energy of ultrasonic frequency (over 16KHz) to connect the same kind of metal or dissimilar metals. When metal is ultrasonically welded, neither electric current nor high temperature heat source is applied to the workpiece, but under static pressure, the vibration energy of the frame is converted into friction work, deformation energy and limited temperature rise between the workpieces. The metallurgical bonding between the joints is a solid state welding that is realized without the base material melting. Therefore, it effectively overcomes the spatter and oxidation caused by resistance welding. Ultrasonic metal welding machine can perform single-point welding, multi-point welding and short strip welding on thin wires or sheet materials of non-ferrous metals such as copper, silver, aluminum, and nickel. It can be widely used in the welding of SCR leads, fuse pieces, electrical leads, lithium battery pole pieces, and tabs.

2) Principle of ultrasonic plastic welding

When the ultrasonic wave acts on the thermoplastic plastic contact surface, it will produce tens of thousands of high-frequency vibrations per second. This kind of high-frequency vibration with a certain amplitude will transmit the ultrasonic energy to the welding area through the upper weldment. Because the welding area is two The acoustic resistance is large at the welding interface, so local high temperature will be generated. In addition, due to the poor thermal conductivity of the plastic, it cannot be distributed in time for a while, and it gathers in the welding area, causing the contact surface of the two plastics to melt rapidly, and after a certain pressure is applied, it merges into one. When 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.