The main difference between welding and other joining methods like adhesives or riveting is the use of heat. However, there are two ways heat can be applied, so welding techniques are divided into two categories. The first and more common category involves direct heating methods like TIG and MIG welding. Ultrasonic welding falls under the second category, which is less common and involves indirect heating.
Ultrasonic welding generates the heat needed to join two parts through ultrasonic vibrations. This article discusses various welding techniques and their applications in manufacturing parts.
This is an indirect heat welding process that uses ultrasonic waves to weld thermoplastics and thin metal parts together.
The machine works by converting high-frequency electrical signals (20-40 Hz) to ultrasonic waves. Afterward, the generated mechanical vibration is amplified and delivered to heat and weld the two parts.
The welding process is unique, unlike other processes such as MIG and TIG welding, which need filler materials. Also, it is suitable for welding small and thin parts due to its precision and accuracy compared to other direct sheet metal welding processes.
Its advantages include quick setting time and clean welded joints. Consequently, it is a joining mechanism in the medical, electronics, and automotive industries.
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Before the discovery of ultrasonic welding in the 20th century, the prevalent plastic welding processes were arc welding techniques. However, these welding techniques produced heavy and unwieldy parts. Therefore, the introduction of an ultrasonic vibration for welding plastics was a welcome relief for many industries.
Ultrasonic vibrations were first applicable in welding hard and compatible plastics. Here, it involved using a probe that touches the two parts to weld them together. Consequently, at that point, it became an important part of the aircraft construction industry ahead of spot welding.
The modern development and use of the welding technique would be attributed to Robert Soloff, a lab manager at Branson Instrument, who mistakenly discovered that the ultrasonic probe does not need to touch thermoplastic parts to weld them.
Soloff developed Sonics & Materials, and in 1965 was awarded the patent of the welding process together with Seymour Linsley. He later presented the idea to Ideal Toy Co., which the company accepted due to the aesthetic yet strong welded joints. Consequently, this led to a boom in plastic toy production and the acceptance of important parts of several commercial products.
Ultrasonic vibration use in the welding process underwent several modifications. Currently, it is a common technology with both consumer and industrial applications.
The machines comprise several parts with specific functions. Below are a few important parts you will find in all types of ultrasonic welding machines:
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Generator
The generator converts electrical power with a resonance frequency to the required voltage and high frequency. In addition, it has a microprocessor responsible for driving the welding cycle and providing important welding communication through the user interface.