When ultrasonic waves act on the contact surface of thermoplastic, it will produce tens of thousands of high-frequency vibrations per second. This high-frequency vibration with a certain amplitude will transfer ultrasonic energy to the welding area through the upper weldment. Due to the large acoustic resistance in the welding area, that is, the interface between two welds, local high temperature will occur. Due to the poor thermal conductivity of plastics, they could not be distributed in time for a while and gathered in the welding area, which led to the rapid melting of two plastic contact surfaces, and after a certain pressure, they merged into one. When the ultrasonic wave stops working, let the pressure last for a few seconds to make it solidify and shape, so as to form a solid molecular chain and achieve the purpose of welding, and the welding strength can be close to the strength of raw materials. The quality of ultrasonic plastic welding depends on the amplitude of the horn, the applied pressure and the welding time. The welding time and horn pressure can be adjusted, and the amplitude is determined by the transducer and horn. The interaction of these three quantities has a suitable value. When the energy exceeds an appropriate value, the melting amount of plastic is large, and the welded object is easy to deform. If the energy is small, it is not easy to weld firmly, and the external pressure should not be too large. The optimum pressure is the product of the side length of the welded part and the optimum pressure per 1 mm edge.
Principle of ultrasonic metal welding
The principle of ultrasonic metal welding is a special method to connect the same or different metals by using the mechanical vibration energy of ultrasonic frequency (above 16KHz). When ultrasonic welding metal, neither current nor high-temperature heat source is applied to the workpiece, but only under static pressure, the vibration energy of the wire frame is converted into friction work, deformation energy and limited temperature rise between the workpieces. Metallurgical bonding between joints is a kind of solid-state welding that does not melt the base metal, so it effectively overcomes the splash and oxidation caused by resistance welding. Ultrasonic metal welding machine can weld thin wires or sheets of non-ferrous metals such as copper, silver, aluminum and nickel by single point welding, multi-point welding and short strip welding. It can be widely used in SCR leads, fuse pieces, electrical leads, etc.