Essay On Ultrasonic Welding

Ultrasonic welding is one of the commonly used technique for welding the thermoplastic materials. This is because it is the by far swiftest known welding technique available. The time of welding in the ultrasonic welding is normally well within a second i.e. less than 1 second. Ultrasonic welding process utilises high frequency and lower amplitude for welding. Frequency is of the range 20 to 40 KHz and amplitude ranges from 2.5 µm to 0.25mm. Ultrasonic welding is preferred for welding thermoplastic materials in mass production. Weld quality of ultrasonic welding is higher. In this welding technique, the ability to join two components or parts depends on the material properties, frequency of welding, joint design and welding amplitude [10-13].

Theoretically Ultrasonic welding process is actually made up of five different but highly coupled sub processes. They are

a) Mechanics and vibrations of the tool parts,

b) Viscoelastic heating of the thermoplastic material,

c) Heat transfer through the thermoplastic,

d) Flow and wetting and

e) Intermolecular diffusion [11].

The generated oscillations from the applied electrical power at high frequency of the order of 20 kHz to the piezoelectric transducer. The oscillations produced by the transducer are very small, so a booster is connected to the transducer in order to increase the amplitude of vibration [14]. Thus produced mechanical vibration is then transferred to the metal horn which induces ultrasonic sound waves. This energy is used for welding the components. A high quality weld can be obtained through ultrasonic welding even at a larger relative distance from the site from where the mechanical vibrations are introduced. Ultrasonic welding can provide a very high quality weld with materials having good acoustic properties [15,