Bonding - More than materials | Herrmann Ultraschall

André Husson measuring a sonotrode in the sonotrode measuring laboratory. ANDRÉ HUSSON BORN IN 1963, CLASS- MATE OF THOMAS HERRMANN. SKILLED PRECISION MECHANIC AND AT HERRMANN ULTRA- SCHALL SINCE 1990. INITIALLY IN MECHANI- CAL SONOTRODE MAN- UFACTURING, NOW IN THE SONOTRODE MEASURING LABORA- TORY. WAS HIRED TO DEVELOP SONOTRODE MANUFACTURING IN THE USA BUT ULTI- MATELY REMAINED IN KARLSBAD. HOW A SONOTRODE IS PRODUCED With the finite element method (FEM), the procedure is no longer as compli- cated and obscure as it was 30 years ago, when André Husson started out at Herrmann. This is despite the fact that the components and machines have actually become much more complex. The sonotrode ordered by the custom- er is first calculated on the computer. Information about the properties of the sonotrode material used and the plastic to be welded is used to perform the calculations. And of course, what the finished piece should look like – the computer supports the designer in developing a suitable sonotrode. TURN NEGATIVE INTO POSITIVE The digital model becomes reality in the machining: A machine cuts the component from a piece of titanium. This can sometimes take up to 20 hours, depending on the size and complexity of the application. The mill- ing machine works accurately to the hundredth of a millimeter, cutting piece by piece out of the titanium. “It used to be trial and error. Many sonotrodes from expensive titanium ended up in the scrap heap,” says Husson. “Today, we know exactly what it must look like so that it vibrates in reality just as the designer planned with the digital model.” But sometimes the plans and the reality are worlds apart. This is where André Husson and his colleagues from the measuring laboratory come into play, after the finished sonotrode has been milled in the in-house machining department. “The part is a negative of the applica- tion,” Husson continues. “It is inserted, the sonotrode comes from above, and within a few seconds two parts are welded to each other.” FIT FOR THE APPLICATION Very simple – actually. However, there is a lot to consider, especially if the application is not planar, and has an uneven shape. “The sonotrode must be designed so that it does not leave behind any marks, no material gushes out of the weld joint. Either of these would cause the customer to discard their product. Additionally, the sono- trode must bring an even amplitude distribution onto the application, oth- erwise it would not weld at all points.” This, too, would result in too many rejects, which is not in the interests of the customer and the sustainability principles of Herrmann Ultraschall. QUALITY AND CUSTOMER SATIS- FACTION ARE HIS OBJECTIVE To check the finished sonotrode, one option is to listen to it. “If it screeches loudly, something is not right,” says André Husson. Using state-of-the-art laser technolo- gy, today it is measured in its vibrating condition and the result is recorded. “The laser vibrometer measures the sonotrode and not only shows chang- es of amplitude, but scans them and creates a three-dimensional image,” says Husson. This allows him and his colleagues to see where the tool vi- brates, and how. “Additionally, we use it to do a frequency scan and make the movement visible. We thus ascer- tain all the frequencies with which the sonotrode could be made to vibrate. This is important so as not to induce the wrong frequency.” That would make the tool unusable. However, thanks to the computer, the designers are able calculate everything exactly beforehand – “so we in the measuring laboratory are not needed so often anymore,” says Husson with a laugh. “The fundamental objective of our company is to deliver the best quality; only in this way can we guarantee the customer the best possible sonotrode for their requirements,” says Husson with conviction. Regardless of whether it is a large order or “just” a spare part that has been ordered. “I sign the measurement report and would like “IT USED TO BE TRIAL AND ERROR. MANY SONOTRODES FROM EXPENSIVE TITANI- UM ENDED UP IN THE SCRAP HEAP.” our ultrasonic tool to leave the building ‘in good conscience.’” Countless sonotrodes have already gone through André Husson’s hands, and in the case of many he can still remember even years later what was wrong before his optimization. After 30 years of sonotrode optimizations, André Husson wanted to experience it again. In the spring of 2021, he moved to METALS application development, in order to provide targeted support to and help develop the youngest busi- ness unit with his specific expertise. 53 52