Efficient Small Series Production for Electromobility

Jigless laser-welded low-cost battery pack housing made of high-strength aluminium (Source: WZL RWTH)

In addition to general trends and challenges in automobile production, such as shorter innovation cycles or individualization, especially electromobility is a new factor in increasing the number of variations in the production of different vehicle types. At the same time, the production volume per vehicle type is decreasing, so that production costs can be allocated to fewer and fewer vehicles. This requires efficiency enhancement measures to achieve high product quality with less effort even in small-series production. Therefore, the re-search project “Production Efficiency in Small-Series” (ProeK) investigated new, practice-oriented technical solutions to enable small series production in the future field of electromobility to be as cost-effective, efficient and flexible as possible.

In order to map the efficiency improvements in the production of key components, the research project was divided into two subprojects: “Shell” and “Body”. The project partners involved covered the competencies required for a successful processing of the project: electric vehicle manufacturers Street-Scooter and e-Go Mobile, the component manufacturer body and joining technology expert LBBZ, the FH Aachen and the vehicle production department of the Laboratory for Machine Tools and Production Engineering WZL of RWTH Aachen University (research partners) and Trumpf as an associated partner.

The subproject “Body” focused on reducing expenditure and conserving resources in fixture construction. The concept of jig-free joining by means of plug-in connections of the components as component-integrated jig functions was further developed based on new body components specific to electromobility, such as the battery pack housing. A corresponding alternative production chain from component manufacturing to the joining concept allows greater flexibility and material savings when using edge components and laser beam welding processes. A comprehensive design methodology was developed for the use of component-integrated jig functions instead of jigs and fixtures as additional operating resources. In addition to the plug connections, the total number of required components could be reduced by a more efficient production and join-ing concept for vehicle frames made of profiles.

Within the subproject “Shell”, the emphasis was on reducing the effort and saving resources in quality adjustment and assurance. For this purpose, different concepts for an integrated adjustment process were investigated, for which tools for adaptive quality adjustment were developed. This included the use of additive manufactured tolerance compensation elements as well as the use of cross-linking and machine learning for the adaptive adjustment of joining processes. In the course of the second mentioned technical solution, a cost-effective sensor concept was developed, which promises significant investment and effort savings compared to the classical downstream quality assurance. The integrated adjustment process reduces scrap and rework. The reworking, which is still required, albeit less, was supported by additively manufactured gauges for the adjustment of exterior components and by tool guidance.

In close cooperation between the partners involved, the two subprojects have thus made it possible to research solutions for more efficient small-series production along the value chain of electric vehicle production. These solutions are not only the basis for further developments by the application partners e-Go Mobile, Street-Scooter and LBBZ: These solutions have already been applied in practical implementation in the corresponding productions and have led to patents, for example for additively manufactured adaptive hinges. The technical solutions developed and the corresponding implementation concepts thus make a sustainable contribution to electromobile production in North Rhine-Westphalia.

The research project “Production Efficiency in Small-Series” (ProeK) was carried out between 2017 and 2020 and was financially supported by the European Regional Development Fund ERDF. (Source: WZL RWTH)

Link: Production efficiency in small series production, e.GO Mobile AG, Aachen, Germany

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