Launching a new electric vehicle (EV) on the market presents a multitude of challenges, especially for new OEMs. One of the biggest challenges is the development and production of the car body. The FlexBody, designed and developed by FEV and Imperia, is a construction kit for low and medium vehicle production volumes that enables the OEM to produce, in the shortest possible development time and in line with target costs, a lightweight car body construction consisting of a profile-heavy design for its individual target vehicle.
For so-called purpose electric vehicles, it is not economically viable to produce conventional, self-supporting car bodies made of steel or aluminum sheet metal due to the very high preliminary investment costs. Also, the development process leading up to series production is usually time consuming, which means a long wait until market launch.
FlexBody is a flexibly configurable structural car body kit that was developed by Imperia together with partners from research and production. The idea behind it is to develop and produce car bodies at a technologically high level at an affordable price. Compared to a self-supporting car body as well as the traditional space frame, FlexBody is impressive due to its very low investment costs and is particularly attractive for an annual production volume of under 10,000 units.
The Principle of FlexBody
A FlexBody car body structure is particularly suitable for the so-called multi-material bodies, or car bodies that are developed in a multi-material, mixed construction approach. It consists of profiles that are joined with the help of structural “nodes” using a suitable joining procedure.
To quickly find an optimal combination of materials and construction methods based on the cost/benefit ratio, a comprehensive knowledge base regarding unit-dependent costs for the individual production technologies is stored in FlexBody. Only those production processes are taken into account that generate low investment costs. This is accompanied by an analytical preliminary estimate of the occurring loads, e.g. regarding crash performance and stiffnesses. This means that the initial draft of the structure possesses a high degree of maturity and that it can be subsequently used to start virtual validation. This method considerably shortens the development process compared to traditional series development.
In addition to traditional manufacturing processes that are used for profiles and nodes, new manufacturing processes such as “industrial origami” and hybrid casting have been developed for use in the FlexBody.
Industrial origami is a sheet metal construction method that is used to produce comparatively complex geometric shapes for creating profiles and nodes. Following the Asian paper-folding technique and using lasers for blank cutting and the joining processes, structures are generated from a mix of folding and simple, individual metal sheets based on the required geometry and the different wall thicknesses. Moreover, high-strength to ultra-high strength steel grades are used that can only be found in large-scale production due to lack of availability. Origami configurations in aluminum are also possible.
Hybrid casting is an innovative procedure for producing the nodes. The profiles made of different materials to be joined are cast and then accordingly joined directly to the highly integrative structural cast nodes.
>>THE FLEXBODY PRODUCTION CONCEPT IS COMPLETELY DESIGNED FOR LOWER TO MEDIUM PRODUCTION QUANTITIES
The production concept is also completely designed for lower to medium production quantities. Instead of the conventional KTL coating process used in large-scale production of the overall car body, targeted component coatings save time and money.
Instead of many individual assembly groups (ZSBs) each with the necessary assembly equipment, the profiles and nodes are completely assembled in the “singleshot fixture.” A special tolerance concept is included in the assembly process. Using just the one “singleshot fixture” and based on 3-shift operation, up to approx. 7,000 car bodies can be produced annually. At the same time, this production concept is easily scalable by operating several fixtures simultaneously to increase the production volume.
The components can be joined preferably using injection adhesives. This process involves injecting the cold- or hot-curing structural adhesive into dedicated spaces between the profiles and nodes inserted into one another. The empty space between the inserted components forms a sort of cavity that absorbs the adhesive. Aside from the multi-material mix, this process also creates tolerance compensation. The singleshot fixture ensures the positions of the parts in the specified tolerances. Special equipment and a constructive knowledge base ensure the adhesive seal in the inner and outer transition points.
The FlexBody car body construction kit is a new product which covers the whole process from development to series production of e-vehicle light-weight bodies for lower to medium production quantities. Special highlights include the methods, construction and production technologies developed in-house that stand out considerably from conventional construction methods.