Xfurth Ltd Blog

Ultrasonic welding is a relatively new bonding technique that is evolving all the time. Originally discovered in the 1940's, ultrasonic welding uses ultra-high frequency sound waves to bond materials. The fundamental principle is extremely simple; when an ultra-fast frequency soundwave is introduced to some materials, they melt.

This form of bonding technology is unique because of the control that it offers, and its ability to join dissimilar materials. It is used extensively in the aerospace, automotive, medical and plastic manufacturing industries, but in recent years ultrasonic welding has also been utilised in the manufacture of electronics as well. Because all of the heat is localised in the weld area, this method can be used to bond very fragile materials together.

Xfurth Ltd – Providing products and services formerly offered by Herfurth UK Ltd.

Xfurth was formed by the former staff and employees of Herfurth UK. This followed the closure of Herfurth UK as a result of a decision by the major shareholder who no longer wished to continue the business.

The Press

The press in an ultrasonic welding system provides the necessary force that must be applied during the welding process. A mounting is provided to carry the transducer/booster/sonotrode assembly often collectively referred to as ‘the stack’. The application of a controlled force is critical in any ultrasonic welding application, as the power drawn from the generator is directly affected by the applied pressure. The press must therefore provide a rigid mounting and an accurately applied downforce. With very few exceptions all ultrasonic welding presses are pneumatically operated, the fact that air cylinders provide an exponential rise in force when compared to time is often beneficial to the welding process. Some modern presses also have the option of an attached linear encoder to further enhance the control of welding depth.

The process of ultrasonic welding was first used in a production environment in the early sixties. The early machines had very basic generating systems, were prone to overload problems and due to lack of widespread understanding of the process it was seen very much as a ‘Black Art’. During the 1980’s the control systems, with the introduction of microprocessors, became more complex allowing printed recordings to be produced. This development led to a greater understanding of the process and in turn led to further developments of the generating system to include overload protection and automatic frequency control.

As well as the shape of the moulding, the information about material provided by the manufacturers of the raw materials can also be referred to for a first general assessment of the ultrasonic welding response of thermoplastics. Of this data the following items permit approximate conclusions to be drawn about the welding response.