35 Battery sealing | Focus E-Mobility Engineering | May/June 2024 Fully-automatic inline hot-riveting systems have been developed for the hot air process. Up to 12 rivet points can be processed as standard, with an integrated transport system bringing the workpiece carrier or panel into the manufacturing cell. The component is processed in the cell in the required cycle time, which is determined purely by the heating cycle rather than the riveting time. For larger battery packs, a larger machine takes the assembled component from the conveyor belt to the processing stations and automatically returns it to the conveyor belt after processing. The concept, as a modular platform, enables the construction of several stations for a high number of riveting points and/or processes in a hot-riveting system. Plasma cleaning Bonding is becoming increasingly important in modern industry. Mixed material connections (so-called sandwich connections), complex geometries, new materials, minimal amounts of adhesive – these are all challenges that material and system manufacturers have to face. For a long time, plasma has been used to improve adhesion; i.e. cleaning and activating surfaces. Plasma ensures impurities are removed from the surface and functional groups are created. This leads to several effects. On the one hand, the wettability of the surface is increased, so that the applied material can be optimally distributed over the surface. On the other hand, the functional groups form a strong bond with conventional adhesives and casting compounds, and thus ensure better, more long-term, stable adhesion, strength and tightness of the connection. In preparation for subsequent processes, such as bonding and coating, the surface is pretreated using plasma technology, so unwanted raw materials and dust particles are removed. Plasma technology makes it possible to further process the materials immediately after plasma cleaning. The surface of plastics, metals and other materials is changed through the use of plasma technology in such a way that the surface tension increases to the desired level, thereby significantly improving wettability. Plasma treatment and plasma cleaning optimally prepare surfaces on plastics, metals and many other materials for subsequent processes, such as bonding and coating. The material surfaces are removed in the gentlest way from unwanted raw materials and even the smallest dust particles. Safe plasma fine-cleaning removes additives, hydrocarbons, mould-release agents and Depending on the application and specification, different caulking methods are used. All in all, only thermal riveting processes can be used, as both the electronic components and metal sheets must be processed without vibration. The size and weight of the modules, along with the high number of rivet points located at short intervals, means a custom system must be developed for the hot-riveting process for the battery packs for both prototyping and series production. The hot air heat-staking process separates heating and forming, so they can be carried out in parallel by two modules in two stations, allowing the cycle time of the machine to be significantly reduced. A particular advantage of this process is that it always ensures consistently good riveting results without melt leakage, even over high-volume fluctuations due to component tolerances. Sealing battery packs (Image courtesy of bdtronic) Sealing the battery pack is a key challenge (Image courtesy of PPG)
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