Lightweight Construction

Casting of Lightweight Components

| Editor: Janina Seit

Although casting is an ancient process, it has not become a boring topic. As Dr. Achim Keidies and Dr. Wolfgang Knothe from Franken Guss explained at the Lightweight Construction Summit in Würzburg, Germany, casting processes offer numerous solutions for lightweight construction.

As early as 3000 B.C., people had already cast metals for production of tools.
( Source: Pixabay / CC0 )

At the Lightweight Construction Summit, the two managers of Franken Guss GmbH & Co. KG, Dr. Achim Keidies and Dr. Wolfgang Knothe, demonstrated in many examples how it is possible to save a considerable amount of weight by applying component design prior to the casting process. However, this requires comprehensive knowledge of the materials and their properties, as well as of the advantages of certain component geometries. Especially the design of components according to bionic principles offers promising potential for applications in the field of lightweight construction — much more promising than the development of materials and processes. In this case, notch resistance is of particular importance, as adapted radii significantly increase the resilience of the components. Another aspect of lightweight technology is the possibility to remove non-essential layers of material at areas that are only exposed to low levels of stress.

Dr. Achim Keidlies (right) and Dr. Wolfgang Knothe of Franken Guss presented casting processes that support lightweight construction at the Lightweight Construction Summit.
Dr. Achim Keidlies (right) and Dr. Wolfgang Knothe of Franken Guss presented casting processes that support lightweight construction at the Lightweight Construction Summit.
( Source: Stefan Bausewein )

The opposite can also be quite beneficial: If, for example, additional material is added to local areas exposed to maximum stress levels, its supporting effect can compensate for the high structural loads. To this end, Franken Guss relies on extensive and very detailed simulation methods, which rely on iteration loops to determine the optimum geometry on a computer screen. Casting is ideally suited for this kind of design procedures, as it offers maximum freedom of design. New components can be adapted exactly to the pre-calculated load cases.

Key Parameters of Material Selection

In addition to the design of the components, a clever selection of materials can facilitate lightweight construction. The material behavior in static and dynamic load cases as well as in the event of a crash are key parameters that have to be considered in the selection of the right material. This not only concerns the stability of the material, but also its modulus of elasticity. A highly robust material may significantly increase the stability of the component, but it may also have a negative impact on its notch resistance. However, the choice of material also depends on the geometry of the components and on the casting process. For extremely thin-walled lightweight components, Franken Guss recommends castings such as vermicular graphite, since its microstructure is optimally suited for these critical casting processes and the very small tolerances involved.

Thanks to almost 100 years of expertise in iron and aluminium casting, Franken Guss has already developed many innovative components. A current example is a swivel bearing for commercial vehicles, which — thanks to geometry optimization — is 30 % lighter than the first component design. Another highlight is the reinforced frame head in a truck series. The previously forged component is not only 15 % lighter than a cast part, but now also integrates the functions of nine individual parts. Lightweight iron casting can even be used instead of aluminum, which in fact is the typical prototype material for lightweight constructions. Franken Guss has for instance bionically optimized a cast iron pivot bearing for Audi in a way that made it almost as light as a comparable aluminium component.

This article was first published by Automobil Industrie.

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