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Age of enlightenment

Replacing metal with plastic has huge potential to make vehicles lighter and more fuel-efficient. In order to be able to replace as many sheet steel and aluminum components as possible, ElringKlinger engineers are not only working on classic plastics but also on innovative hybrid materials and the requisite production processes.

ElringKlinger front-end cockpit carriers combine the benefits of metal and plastic, or in other words: maximum strength and minimal weight.

There is a clear, worldwide trend towards lower carbon emissions and less fuel consumption by vehicles. A limit of just 95 g of CO2 emissions per kilometer will apply to all new vehicles in the European Union from 2020. Since the weight of any vehicle plays a significant role in generating carbon emissions, ElringKlinger engineers are continually working on new lightweight solutions for drivetrains and bodywork. “In order to meet these emission targets, we will have to harness the full potential of lightweight engineering,” says Klaus Bendl, Head of Development in the Elastomer Technology and Modules division of ElringKlinger. “Although we have already achieved a great deal, there is certainly further potential to make vehicle components lighter and more sustainable.”

One key approach in this drive for weight reduction is to replace metal parts with plastic ones. “For about 15 years now, we have been working step by step to replace metal with plastic in the drivetrain,” says Bendl. “We began with modules for cylinder head covers and then started replacing metal parts in the intercooler duct with plastic parts. Today, our focus is on components such as oil separation systems, intake modules and oil pans made of plastic – the latter of which are particularly suitable for use in utility vehicles.”

Large plastic components offer more than just weight savings. The production processes continually being developed by ElringKlinger result in a significant reduction in the number of overall parts.

There is a double benefit to using plastic in this way. For one thing, weight reduction of up to 30 percent – and even 50 percent in many cases – can be achieved. But functional benefits can also be gained at the same time: “Plastic allows us to achieve much more complex geometries,” says Bendl. “Thanks to the additional options afforded by injection molding, we can use plastic components to keep the number of individual parts as low as possible.” For instance, a plastic oil intake module has been successfully developed as a single component – replacing four individual parts. The aspect of production is taken into account as soon as such components are developed. Bendl and his colleagues benefit from the in-house expertise of development partner Hummel, the company that produces the injection molding tools. “These functional advantages add to the weight-reduction benefits, making our lightweight solutions attractive from an overall costing perspective,” says Bendl.

A new area now being addressed by lightweight construction experts is vehicle bodywork. Here developers are focusing on cockpit cross-car beams and front-end carriers made out of polymer-metal hybrids. “We use hydro-formed hybrid technologies to make these structural components,” says Reinhard Müller, Head of Elastomer Technology and Modules. “This is a brand new system currently not offered by any other supplier. For us, it is the perfect foray into lightweight bodywork, as we can not only achieve weight-reduction benefits of 20 to 30 percent but also produce these components at very competitive rates.”

Plastic meets metal – hydroformed hybrid technology (HFH)


PREPARATION

The metal tube is placed in the mold by a robot and filled with water.

FORMING

The water is subjected to 600-bar pressure so that the tube will assume the desired shape.

INJECTION MOLDING

Liquid plastic heated to a temperature of 300 degrees Celsius is injected into the mold at 600-bar pressure. It then solidifies in the cavity and around the reshaped tube.

DOWNSTREAM PROCESSING

The hybrid part is then removed from the mold and transferred to the downstream processing stage.

Hydroformed hybrid technology (HFH) involves a combination mold tool that combines the two processes of hydroforming and plastic injection molding in a single step. A robot places an extruded, thin-walled metal tube into the mold. After the two halves of the mold are closed, the interior of the tube is filled with cold water at 600-bar pressure, which causes it to expand and assume the desired shape. The injection-molding process then begins in the same mold cavity.

Molten plastic is injected into the mold at 300 degrees Celsius and then solidifies in the cavity between the mold and the reshaped tube, once again at 600-bar pressure. “The internal counter-pressure ensures the aluminum tube does not collapse during the injection process,” explains Bendl. Once the part has cooled and is thus dimensionally stable, the hybrid part is then removed by a robot and transferred to the downstream processing stage. This process allows a host of plastic elements to be incorporated in a cockpit cross-car beam or front-end carrier in a single processing step and then formed into their final shape. By contrast, when all-metal materials are used, several different steps are required, because each individual piece of metal has to be produced in separate molds and then attached by welding robots.

Precision work – parts produced by the hydroformed hybrid method meet the highest safety standards.

Polymer-metal hybrids combine the strengths of both materials. These include not only technical advantag­es such as a great dimensional and geometrical accuracy with minimal tolerances and increased bending and dent resistance in the event of a crash but also time and cost savings resulting from the ability to incorporate several processing steps in a single action. The HFH team is currently working on structural parts for markets in China, North America and South Africa, with production in Suzhou (China) already underway. “We ventured into serial production with a car maker for the first time in late 2014 and are experiencing a very high degree of interest from other vehicle manufacturers,” says Müller. A further production site in Leamington (Canada) for instance is already at the planning stages.

ElringKlinger engineers are also working on other lightweight bodywork solutions, such as structural parts made out of organo sheets that contain no metal materials, but rather continuous woven fiberglass embedded in a polymer matrix. They can be used wherever there is a need to reduce the weight of structural and energy-absorbing parts. To make a part out of organo sheets, the fiberglass-polymer semi-finished part is heated, reshaped and overmolded with plastic.

“For us, it is the perfect foray into lightweight bodywork, as we can not only achieve weight-reduction benefits of 20 to 30 percent but also produce these components at very competitive rates.“

Reinhard Müller, Head of Elastomer Technology and Modules

“Components made out of organo sheets are as solid and resilient as metal. This makes them capable of assuming the supportive function of metal in such components where conventional plastics would be in­adequate,” is Bendl’s summary of the benefits of this material.

Organo sheets are already being used in seating systems, foot pedals, pedal brackets, running boards and crash elements. With the aim of being able to apply this material to other bodywork components, ElringKlinger process developers are working on further refining the processing and forming techniques, because glass fibers are not as ductile as metals. Nevertheless, with the potential to make weight savings of about 30 percent, organo sheets seem likely to be able to replace more and more steel components in the future and thus contribute to achieving the emissions target of 95 g of CO2 per kilometer.