Issue: Sep 2015

Blueprints from nature  help reduce weight

Blueprints from nature  help reduce weight

by James Hilton

In automotive engineering the focus for reducing weight has predominantly been on the use of lightweight materials such as aluminum, carbon, magnesium or fiber composites.

Development engineers at German engineering service provider EDAG questioned whether the lightweight approaches applied to date are really enough to achieve the ambitious weight and emissions targets for the sustainable vehicles for future mobility. So they looked to nature for inspiration. The result is the “EDAG Light Cocoon” concept car.

It is a vehicle which takes the bionic pattern of a leaf as its design basis, and converts it into lightweight, intelligently networked body structures. According to EDAG, the concept that illustrates sustainable methods for the automotive industry and at the same time shows the technological potential of additive manufacturing. The Wiesbaden-based design engineering company has working examples of technology which show that the combination of bionic design and additive manufacturing is not just pure Utopia, and these could soon become reality.

EDAG Light Cocoon

Introduced at the 2015 Frankfurt International Motor Show (IAA), the EDAG Light Cocoon relies on a non-traditional approach to reduce weight. As with the skeleton structure of an organism in nature, the vehicle concept favors an approach in which material is only used in the areas where it is absolutely necessary for function, safety and stiffness. The result is a load bearing, branch-like carrying structure which meets all requirements imposed on structurally relevant components, despite the fact that less material is used. Additive manufacturing makes it possible, for the first time, to create such complex structures. It is a “technology which, on account of tool-free production, will in the future carry extremely interesting economic potential and at the same time offer extremely variable production possibilities,” says Jörg Ohlsen, CEO of EDAG Engineering.

The outer body skin of the EDAG Light Cocoon was inspired by nature. Just like the structure of a leaf, which has a lightweight outer skin stretched over it, a lightweight protective skin covers the EDAG Light Cocoon – although in this case it is made of a textile fabric. Outdoor specialists Jack Wolfskin supplied a tried and tested stretch lightweight fabric that is also extremely weatherproof to serve as the new outer body skin for the project.

In addition, the unusual combination of a skeleton structure and fabric also makes it possible to integrate a new type of lighting concept, which incorporates the complete vehicle. Not only does the LED backlighting system make the structure of the Cocoon visible, it transforms the vehicle into a screen. The look is no longer static. The customer can change the appearance of his car at any time, and select the color of her or his choice. The variable light design is in line with consumer requirements for greater individuality, according to Ohlsen.

Headlights brighter and lighter

Also shown at the IAA was the first fully functioning, ready-for-approval example of a headlight which illustrates the extensive potential of additive manufacturing. This project is a product of EDAG’s new light laboratory. It is pursuing the objective of further enhancing the luminous power of LEDs through an active/passive cooling system. Optimum heat dissipation through additively manufactured bionic cooling structures and a number of other innovative components make it possible to improve the headlight’s performance while at the same time reducing weight. The new degree of freedom provided by additive manufacturing means that branched shapes can be created, and this makes it possible to meet aerodynamic requirements and produce optimum heat dissipating surfaces. What is more, very important market segments in the low-volume and high-performance sectors can be served at lower cost and with significant savings in investment, as the production method involved is largely tool-less, according to the company.

Spaceframe optimization

It is already evident that the EDAG Light Cocoon is a pioneering concept for the lightweight design of the future. In Frankfurt EDAG demonstrated the fact that it is also a solution for another challenge in automotive design: the development of a bionically optimized, hybrid manufactured spaceframe body will make the increasing vehicle variance engendered by the large variety of drive systems and load categories more manageable. The vehicle bodies of tomorrow will not just have to become lighter, but also be more flexibly designed. The manufacturers are also expected to integrate the growing number of drive concepts and energy storage systems in the vehicle structure. The result is an increasing number of vehicle derivatives calling for body concepts that are adaptable and can be produced economically.

At the IAA EDAG, Laser Zentrum Nord (Hamburg), Concept Laser (Lichtenfels) and the BLM Group (Levico, Italy) joined forces to demonstrate the bionically optimized, hybrid manufactured spaceframe, a new approach to bringing about a changeable, flexibly manufactured body concept. Its success lies in the combination of additively produced body nodes and intelligently finished, conventionally manufactured sections. Thanks to additive manufacturing, the nodes can be highly flexible and multifunctional, to enable, for instance, different vehicle variants to be produced on demand in an extremely flexible production cell, without additional tooling, production equipment and start-up costs. Steel or aluminum sections serve as connecting elements. By applying varying thicknesses and geometries, these too can easily be individually adapted to the specified load categories.  The result is a bionically designed, load path-optimized spaceframe structure. As the process uses very little in the way of equipment and tools, it will be possible for all body variants to be produced economically and with the maximum possible flexibility in the future. Further, requirements for flexibility with regard to the ability to respond swiftly to fluctuating production volume requirements, and the adaptability of structural parts during a product’s life cycle in the sense of a “learning and adaptable Industry 4.0 due to additive manufacturing” are also met.

Lightweight electronics

In partnership with Laser Zentrum Nord EDAG has developed a hybrid manufactured housing for an electric vehicle’s on-board charger, which is more than 50 % lighter than a comparable cast housing. The concept is designed to additively produce only the functional elements relevant to efficiency, as this is where the process comes into its own.

At the core of the housing is an ultra-light cooling structure produced using the selective laser melting (SLM). With its cooling channels specially adapted to the heat transfer of the electronics, the aluminum component achieves an unprecedented cooling capacity. Filigree fins inserted into the cooling channels – the likes of which cannot be produced using conventional manufacturing methods – maximize the efficiency factor.

Due to its compact dimensions, the low-cost production of large quantities of the cooling structure is already possible, according to the company. This example shows that it is already possible for additively manufactured aluminum components to be put to practical and economic use in small and medium-sized series.

“With the vision of the EDAG Light Cocoon and our concepts for the swift implementation of additively manufactured components and modules, we hope to provide stimulus for the future of energy-efficient lightweight design and resource-saving production,” says Ohlsen. “As an engineering company we see lateral thinking, working on new technologies and helping to ensure that visions gradually become ready-for-production concepts as part of our task.”

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