Written by Miles Budimir
Senior Editor, WTWH Media
Welding is a process used to join together two materials. These are typically metals but can also be plastics. The main mechanism of welding is heat; the parts to be joined are melted and then fused together during cooling.
The most familiar welding technique involves the application of heat via a direct heat source such as a torch. But a type of welding called ultrasonic welding differs from other direct heat source methods by using sound waves.
The basic process is this – a high-frequency electrical signal (typically in the 20 to 40 kHz range, but can be higher) is converted via a transducer to ultrasonic waves. These ultrasonic waves are then amplified further and sent to a delivery device, such as a probe tip, where they are applied to the materials to be welded together.
At a microscopic level, the high-frequency wave energy acts like friction, heating up the parts for a brief time (usually seconds), causing them to melt and fuse together. Unlike some other welding processes, ultrasonic welding uses no filler material that melts and aids in bonding the materials together.
A typical ultrasonic welder is made up of a high-frequency signal generator, a transducer, a so-called “horn” that makes contact with the materials to be welded, and an anvil where the materials are placed and held down during welding.
Ultrasonic welding is a viable technique for making small welds on relatively thin materials of no more than a few millimeters thick. Thin, malleable metals such as aluminum and copper can be readily joined, as can various kinds of thermoplastic materials.
The benefits of ultrasonic welding make it attractive in many industrial uses. It’s faster than other welding techniques and features a quick setting time, unlike the longer cooling times required with other welding techniques. Ultrasonic welds are also generally clean with little to no touch-up work needed after the fact, saving time and resources. As mentioned earlier, one of the key limitations of ultrasonic welding is the material thickness, with the maximum thickness usually being a few millimeters.
Uses for ultrasonic welding are spread out across industries and applications. For instance, many diverse packaging applications such as sealing blister packs make use of ultrasonic welding. Other applications include medical devices, electronics, aerospace, and automotive applications such as taillight assemblies.