Sensoric Monitoring of the Ultrasonic Welding Process

• Applicants: Professor Dr.-Ing. Christian Bonten; Professor Dr. Marc Daniel Leonhard von Kreutzbruck
• Subject Area: Plastics Engineering ; Measurement Systems ; Production Systems, Operations Management, Quality Management and Factory Planning
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 540761969

Ultrasonic welding is a joining process for thermoplastics where the thermal energy for melting the material is generated by internal friction and interfacial friction. Ultrasonic welding is characterized by its very short process times (< 1 s), which is why it is used in particular in the large-scale production of small and medium-sized components. Here, quantities of up to 50,000 pieces per day can be achieved. Further advantages of the process are the low-cost and robust machine technology and the fact that no filler metals are required for welding. In addition to welding structural, technical injection molded components and fiber-reinforced tapes, the process is used in the packaging industry for welding plastic films and blisters, and in the textile industry for welding nonwovens and fabrics. The significance of the process on the market is given in particular by the very high quantities. However, due to the numerous complex processes occurring in parallel in the joining zone, the understanding of the exact material behavior during the welding process is still low. Even with supposedly optimally set welding parameters, poor welds can repeatedly occur in the manufacturing process, leading to unforeseen component failure. Due to the lack of knowledge about the behavior of the plastic during ultrasonic welding, there is a strong interest in sensor-based monitoring of the ultrasonic welding process. At the present time, it is not yet possible to make a reliable statement about the weld quality from the pure process parameters. In this research project, therefore, methods are to be created with which inline monitoring of the ultrasonic welding process and the weld seam quality are possible. Particularly the nonlinear acoustic vibrations in the welding process are to be analyzed and modeled. The acoustic power density in the component and the nonlinear behavior occurring during the ultrasonic excitation offer ways of determining the course of the process and the characteristic phases of ultrasonic welding. The measurement and analysis of the actually occurring acoustic vibrations during the welding process represents a fundamental innovation and will potentially provide new essential insights into the processes and the nonlinear behavior in ultrasonic welding.

• DFG Programme: Research Grants