In order to connect the plastic components of the opening mechanism with the aluminum of the lid of the resealable lids for the beverage cans developed by Xolution, a joining process had to be found that works quickly and precisely and enables short cycle times for high throughput rates. After extensive tests, the choice fell on ultrasonic welding systems from Telsonic.

The XO closure system from Xolution GmbH, headquartered in Munich, is suitable for all beverage can sizes. Unlike conventional beverage cans, which can only be opened once, the XO-sealed versions have a plastic opening mechanism that closes the can again. In addition, a tamper evident tape is attached over the slider. It tears when first opened and guarantees the consumer that the can has not been opened before. In order to connect the plastic components to the aluminum lid of the cans, it was necessary to find a joining method that worked quickly and accurately and enabled short cycle times for high throughput rates. After all, the lids with the patented closure are already being delivered in millions to the beverage industry worldwide.

Fast and environmentally friendly process

After extensive testing, the choice of joining technology ultimately fell on ultrasonic welding systems from Telsonic. Both technical and economic reasons spoke in favor of this: In ultrasonic welding, an acoustic tool generates high-frequency sound waves. They vibrate the molecules of the parts to be joined, generating heat that breaks up the material boundaries and fuses the materials together. This results in high-strength connections that withstand the 7 bar internal pressure of the beverage cans.

At the same time, the process is fast and environmentally friendly as it does not require any additives and thus supports recycling. The process is reliable and safe, as the welding process depends on a few parameters that are easy to set and monitor. The parameters are the welding energy, force and time as well as the maximum power (P_Max). In this way, in the first process step, four small pin domes are welded quickly and tightly to connect the inner and outer slides through the aluminum cover. In the second step, the tamper-evident band is then welded on.

MAG ultrasonic generator in focus

The ultrasonic equipment consists of four components that system builders can easily integrate: the ultrasonic generator, which generates the electrical high-frequency vibrations, the converter, which converts them into mechanical vibrations, a booster for amplification and the sonotrode. The latter introduces the mechanical vibrations into the workpiece. The converter, booster and sonotrode are mechanically fixed and acoustically tuned to each other.

The generator has a key function, as it not only generates the electrical high-frequency vibrations, but also in the sense of Industry 4.0 the connection to the higher-level automation technology takes over. About the latest bus systems can z. For example, welding parameters can be adjusted and results can be read in real time. In addition, system costs can be optimized because it is possible to switch between different vibration units. The external setpoint specification for amplitude, time, energy and P_Max, as well as soft start for large sonotrodes and frequency autotuning are other features that ensure high process stability. For the production of the can lid with the resealable XO-closure the optimal connection technique was found.