Ultrasonic welding technology

What is ultrasonic sound?

Ultrasonic is the term used to describe sound in the frequency range beyond human hearing from 20 kHz up to 1 GHz, and is a sub-area of the field of acoustics. Seen in physical terms, ultrasonics is the theory of mechanical vibrations in different media.

How is ultrasonic sound generated?

The vibrations are generated by inducing solid bodies or columns of gas to vibrate mechanically. The stimulus is in practice applied electrically, from a generator that creates electrical vibrations. The piezoelectric conversion principle basically used in ultrasonic welding allows the electrical generator output to be converted into mechanical energy with a very high efficiency. This converts electrical vibrations in the ultrasonic range of F = 20 kHz to 1010 kHz into mechanical vibrations of the same frequency.

The ultrasonic welding method.

During ultrasonic metal welding, the electrical vibrations created by the generator are converted in the converter (acoustic converter) into mechanical vibrations, amplified by the amplitude transformer and fed to the workpieces to be welded (absorber sheeting and copper tubing) through the sonotrode (welding tool).

The mechanical vibrations are applied to the workpieces at a certain pressure and are absorbed at the point of contact between the sheeting and the tube, with the result that the two parts rub against each other at their contact interface with huge shearing force. The resulting molecular and interface friction generates heat, leading to welding by means of internal friction.

The advantages of the ultrasonic welding method.

• No need to clean the surfaces specially
• No need for shielding atmosphere
• No need for welding additives
• Low energy consumption
• Short welding times.

At present, ASA uses four ultrasonic welding lines.