K.D. Feddersen: Plastic-metal hybrid structures provide new design possibilities

In terms of weight savings, and therefore also fuel savings, the use of plastic-metal hybrid structures is opening up possibilities for new structural designs in the automotive industry. In this method, an injection mould is used to interlock metal components with plastic in a single step. This hybrid technology utilizes the synergies of the two materials comprising the composite, enabling cost-effective production of multifunctional components.

Peter Wahl GmbH & Co, a leading manufacturer of technically sophisticated hybrid components, received an order for the locking handle of the soft top in the luggage compartment of the new Mini Cooper convertible. The task was to improve the look and feel of the component compared to the previous model, which had a handle made of separate plastic parts bolted to a metal part. To meet the customer´s requirements, Wahl tested a wide array of materials with and without a blowing agent. However, due to the surface requirement, none of these materials proved to be a resounding success.

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An in-depth consultation with the Application Engineering Department of the Hamburg-based plastics distributor K.D. Feddersen (www.kdfeddersen.com) followed. Based on its extensive experience with different handle geometries, a specially modified AKROMID® B, a PA6 from AKRO-PLASTIC, was selected at the plastics distributor´s facility in collaboration with Project Management.

"The special modification of the grades used makes it possible to produce thick-walled components for high mechanical stress without sink marks, while imparting a very good surface appearance and an exceptional feel, which is ideal for handle solutions," explains Heinz-Günter Onken, application engineer at K.D. Feddersen.

"We met with scepticism at first, but after presenting a few components made from the prototype tool we built, we succeeded in convincing the end customer of the positive material properties. We were able to overmould over the metal insert with no sink marks and produce a high-quality surface finish," says Peter Kerber, Project Manager at Peter Wahl GmbH & Co.

Adjustments in the standard production tool were made to further optimise the surface finish and adapt the parting plane to suit the handle application.

Today, the handle levers are manufactured in a fully automated standard production process and are fitted and removed with the help of a handling robot. The complete assembly of the module including the locking unit takes place in a semi-automated process within the injection cycle.

Figure: The component from the previous model (back) was made of several individual components bolted together. The component from the new model series developed by WAHL (front) consists of a metal piece overmoulded with AKROMID ®.

K. D. Feddersen GmbH & Co. KG, Hamburg, Germany

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