Bonding - More than materials | Herrmann Ultraschall

“IN THE LAST TEN YEARS, WE HAVE IMPLEMENTED A FEW PROJECTS THAT WOULD PREVIOUSLY HAVE BEEN UNTHINKABLE DUE TO THEIR DIMENSIONS AND THE REQUIREMENTS.” NO LIMITS ULTRASONIC WELDING CAN DO NEARLY EVERYTHING T he secret of ultrasonics is quickly vibrating welding heads made of metal, called sonotrodes, in frequencies between 20 and 35 kilohertz. That means 20,000 to 35,000 vibrations per second! They must be calculated exactly and produced with care. That in itself is an art. In the last few years, bigger and more com- plex sonotrodes have been manu- factured than was ever considered possible. Chief developer Ulrich Vogler and Stefan Zendler from acoustics on their experience with boundaries then and now. Ultrasonic welding is the intersection of two important disciplines: the physics of vibrating metals for the weld tool and the chemistry of the plastic to be welded. This makes it interesting and challenging. The sonotrodes are adapted precisely to each application, i.e. each component to be welded, and in most cases are specially pro- duced for the one customer. A lot of time goes into the development and construction of these weld tools and a great deal of the special expertise of Herrmann Ultraschall. In the past, the focus was often on getting applications up and running, often purely empirical- ly; today, however, the focus is primar- ily on efficiency and customer benefit. “And this benefit can only be achieved if the customer gets good weld results in their production environment, under different influences such as tempera- ture, humidity, and changing weld applications, in a way that is robust and repeatable, ideally in three-shift operation,” says Stefan Zendler. “This is the goal we set ourselves when we research, simulate, and calculate.” BIGGER DOES NOT NECESSARILY MEAN BETTER “That is why ‘higher and wider, i.e. bigger and heavier,’ is not our objec- tive when creating the tools,” says head developer Ulrich Vogler. “Even- tually, we simply reach a physical limit.” Sonotrodes wider than 20 cm and weighing more than 40 kg would be difficult to use. However, in the last ten years, Ulrich Vogler and his team have implemented a few projects that would previously have been unthinkable due to their dimensions and the requirements. Thanks to developments in computer-supported technology, there are a lot of things that are feasible today that weren’t just a few years ago. VISUALIZATION IS THE KEY “At the beginning, everything was kind of like ‘black magic’ – we knew too little about vibration behavior and the relevant material properties – everything had to be tried out again and again, also causing rejects and loss,” remembers Vogler. “Even today, welding three-dimensional objects is often still a challenge,” he continues, “because you have to generate the optimal vibration energy at every point of the weld joint.” Luckily, the devel- opment of measuring instruments and analysis tools also came to the benefit of ultrasonic welding. Vogler and Zendler agree that the company has achieved quantum leaps over the decades when it comes to the devel- opment of the weld tools. 45