Lightweight design Ultralight seat: Result of new partnerships

Author / Editor: Christian Otto / MA Alexander Stark

In just seven months, several industrial partners developed a feasibility study for an ultralight seat. Not only the most modern technologies were required to this end, but also faster working methods. The result is a hardware prototype for the interior of the future.

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The ultra-lightweight seat concept of CSI Entwicklungstechnik is a current example of the innovative strength of engineering service providers.
The ultra-lightweight seat concept of CSI Entwicklungstechnik is a current example of the innovative strength of engineering service providers.
(Source: CSI)

Current developments point to a shift towards pure electromobility regarding drive technology. This will likely lead to the elimination of familiar disciplines involved in conventional drive technology. However, there is new potential in other vehicle areas. For example, in the vehicle interior: This aspect will probably go beyond classic individual mobility in the future. The seat will play a crucial role. Vehicle concepts in the field of micromobility, People Movers or so-called air taxis expand the field of application of seats, while entailing more complex demands at the same time. Aware of the high long-term relevance of the system in the much-cited interior of the future, several companies have therefore combined forces: Their goal was to establish a vehicle seat concept that rethought this discipline under the premise of ultra-light construction.

One of the three initiators was the Engineering Service Provider (EDL) CSI development technology. Stefan Herrmann, the main person responsible for the project at the company, explains the joint approach: "The goal was to use new technologies and to completely rethink the concept for a seat on a white sheet of paper." Apart from additive manufacturing, this also includes the process technology xFK in 3D.

Lightweight seat weighs only ten kilograms

Further initiators include Alba Tooling & Engineering and the management consultancy firm AMC. Within only seven months since August 2018, they have worked with additional partners not only to theoretically design an ultra-light seat, but also to realize it up to the hardware prototype. They were pursuing a radical goal: Today's minimalist folding shell seats weigh twelve kilograms in the very best case. Often the seat substructure and connections are not included in this weight. The ultra-lightweight seat weighs about ten kilograms (including the seat substructure), depending on the configuration level. This corresponds to a weight reduction of at least 20 %.

A great advantage, highlighted by the initiators, was their close coordination. Each party contributed its own specific know-how. Thus, the EDL focused on the product and thus on idea, styling and concept, as well as on topics such as calculation, simulation and project management.

AMC was responsible for project analysis

AMC also provided the ideas and took responsibility of the project analysis. Above all, however, the company acted in an advisory capacity on the topics of winding and tooling concepts as well as strategic lightweight design and managed the value chain for the core technology xFK in 3D. According to AMC, this is a highly flexible, almost arbitrarily designable, inexpensive and sustainable fiber composite technology for winding components. The glass, carbon, basalt and many other natural fibers of composite materials (xFK) are aligned according to the desired component functions and load collectives and manufactured three-dimensionally (xFK in 3D). This results in spatial, ultralight structural components. The advantages of the process are multidimensional: They range from fiber deposits designed for force and tension absorption to minimal material waste.

Alba tooling & engineering pools the technologies

Alba Tooling & Engineering took over the part of linking the technologies. The company could resort to its expertise in tool and plant construction as well as in component production and seat trimming. The final step was preceded by the manufacturing of the xFK-in-3-D winding tools and other components, such as the fiber fleece mats and upholstery parts. Alba Tooling & Engineering together with other partner companies took responsibility for this as well.

These partners included Covestro, among others. The manufacturer of adhesive raw materials provided their support in the development of the lightweight fiber fleece shell used for the seat. The fibers are solidified with Dispercoll adhesive raw materials and then pressed into a stable fiber mat in the shape of the seat shell. The shell had to be both mechanically stable and comfortable.

Other important components include the backpanel. The company 3D Core developed the prototypes of these complex components on the basis of CAD data. First the mold kits were developed to create the preforms of the two backpanels. Using VA-RTM (Vacuum Assisted Resin Transfer Molding), the prototypes of these components were manufactured in one-piece molds by Alba Tooling & Engineering.

3D Core was thus able to demonstrate that its technology makes it possible to quickly produce functional composite components using simple means as an alternative to 3D printing. This material system also facilitates the transition to series production.

The project started at LTF 2018

The trade fair organizer Reed Exhibitions, the Lightweight Technologies Forum (LTF), the companies LBK and Robert Hofmann also provided important impetus for the completion of the seat. The initiators launched the project at LTF 2018. That's why Olaf Freier, Event Director at Reed Exhibitions, is delighted with the successful outcome: "What began at the LTF as a virtual development project has delivered a remarkable result in the physical completion of the project." LBK was mainly responsible for the winding of the xFK prototype carrying frame.

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In addition to manufacturing the seat trim components, Robert Hofmann also printed various component constellations in plastic and metal, such as the winding bushes for the carbon winding tools. The methods used were selective laser sintering (SLS) for plastics and selective laser melting (SLM) for metals.

Lightweight design as a team effort

A decisive factor for the success of the project was the continuous and uncomplicated exchange of information between all participants. "Of course, sometimes opinions differ. With a lot of negotiating skill and caution you have to include the individual demands of the partners", says CSI manager Herrmann.

Michael Janz was responsible for coordination at Alba Tooling & Engineering. He confirms the special quality of the exchange: "If we had any discrepancies in the design of our prototype seat: We are true to our word. In the automotive world and especially in series development, this typically works differently: via written specifications, change requests, design specifications, material catalogs, etc. But the joint flexibility in the creation of the prototype seat helped us save time and money.”

In this form, for example, the ultralight seat concept deliberately contains neither airbags nor detection systems: "Now that our prototype phase is complete, the seat is comparable to other prototype seats. Logically, however, the seat has not yet been put through its paces by real component tests or overall seat tests, as is usual in series development, i.e. validated in the conventional series development process. This cannot be achieved in such a limited time. During the virtual design of the seat, CSI and AMC took the most relevant load cases into account in the calculation and simulation. Of course, the comparison of development times for automotive interiors of about three years with the few months we achieved is not accurate." But he also emphasizes: "Many other prototype studies take significantly longer until they are available as a physical object with the latest materials and technologies.”

3D Printing is reduced to the essentials

The exchange of the respective technology know-how was an additional added value for the initiators and partners. For example, CSI met xFK in 3D for the first time and is now planning to further intensify its cooperation with AMC beyond the project. Alba Tooling & Engineering, on the other hand, was able to push the topic of 3D printing in a new area. "We're reducing 3D printing to the essentials. We don't want to produce the whole upholstery in this way, but only parts. We produce a hybrid and combine it with our other processes. Subsequently, integration and cost-effectiveness are improved because we integrate individual parts of a complete seat," explains Michael Janz. Finally, the company targets hybrid 3D printing.

Use of the seat: Hypercars and aerospace

Currently, the integration of the seat into a Hypercar would be a possible option. In this vehicle class the weight reduction would bring a considerable advantage. Stefan Herrmann also believes that it is possible to step out of this niche in the long term. One example would be the expansion to the field of aerospace, i.e. to the so-called flight taxis. "As CSI, we are not yet visible in the field of air taxis. But we can use the project to gain initial visibility," says Herrmann.

In addition to the weight reductions, the project also has an expansion stage that could make it attractive for industry participants in the long term: According to Herrmann, the structure of the seat could be made of natural fibers. This is in line with the megatrend of sustainability.

This article was first published by Automobil Industrie.

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Original: Svenja Gelowicz / Translation Alexander Stark