Plastics/metal hybrid technology renders weight savings in auto airbag assembly


A hybrid plastics/metal airbag housing with integrated lead frame, co-developed and produced by Belgium-based Quadrant Creative Molding & Systems (QCMS) for an automotive steering wheel airbag assembly, has resulted in weight savings, packing space and costs. The assembly is being fitted on vehicles produced around the world.

The integrated lead frame activates the horn when the driver presses the airbag cover in the centre of the steering wheel, completing an electric circuit. As such, the module is a safety-critical component, so design and manufacturing requirements are demanding. It is produced by injection moulding a 40% glass fibre-reinforced polyamide over a pre-coated stamped steel plate.

QCMS), being a full-service supplier, accepted the challenge to work with its partners along the supply chain on the development of a fully automated production/assembly/quality control process, within a tight schedule.

The airbag housing contains the airbag itself as well as the gas generator, with its main function being to direct the airbag during deployment, by maintaining the form and integrity of the housing. The design of the housing, as well as the polymer processing technology used to make it, is of prime importance to this. The hybrid structure is created by combining the plastics housing with the metal leadframe. During development, the metal part within the plastics part was shown to induce additional stresses during the deployment; these were eliminated using FEM analysis and design changes.

The overmoulding process is carried out fully automatically in a purpose-built manufacturing cell at the main QCMS plant in Tielt, Belgium. A six-axis robot positions the leadframe into the mould. The reinforced polyamide is then injected around it. After moulding, the finished product is removed from the mould and placed in a neighbouring station that carries out a 100% quality check. Once the part’s quality is assured, it is positioned on a conveyer belt that takes it to downstream assembly operations.

The plastic/metal hybrid moulding has replaced an assembly of cables on a full steel housing that was more complicated and costly to produce, heavier, and which took up more packing space.

It was first designed for the Ford Transit van, which is assembled in Turkey. Production began in 2012. The success of the design has led to Ford introducing it on four other vehicle models. QCMS ships parts from Tielt to locations in Europe, US, Brazil and India for integration into complete airbag assemblies.

The hybrid integrated lead frame fits in with the continuing trend in the automobile industry to reduce not only weight for savings in fuel, but also space—to allow room for the growing range of increasingly sophisticated safety- and entertainment-related devices now fitted to vehicles, especially in and around the steering wheel—and, of course, costs.

QCMS has operations in Budapest, Hungary, and acts as a main partner to manufacturers across a range of industries, in the creative development and production of polymer-based parts and components for critical systems.


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