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BMW uses Maximator water assist technology in CFRP


Maximator in Germany has further developed water assist technology for the high-pressure resin transfer moulding (HP-RTM) process with a particular automotive carbon fibre reinforced plastic (CFRP) application. This is the first time the company has adapted a water assist system (normally used in injection moulding) for use in structural fibre reinforced composite processing.

At Fakuma, René Himmelstein, vice president sales and marketing for units and components at Maximator, spoke about the equipment supplied to BMW’s plant in Landshut, Germany, where it is used for a curved round-section CFRP roof carrier structural part of the new BMW 7-series car.

The new BMW 7-series car was launched at the IAA automotive industry fair in Frankfurt am Main, Germany in September and BMW meanwhile refers in TV adverting spots to its extensive use of carbon fibre in the car.

Maximator equipment installed at BMW in Landshut consists of a water treatment unit and a pressure unit. These have been tailor-made for the application at BMW, as has the special water injector with multiple integrated monolithic valves, resulting in it being much larger and heavier than injectors conventionally used with water assist injection moulding, Himmelstein said. Key to successful implementation in HP-RTM is the close proximity of the valves to the pressure unit.

Himmelstein said the type of component involved has previously had a foam core, around which carbon fibre braiding is first applied, prior to impregnation by injection with epoxide resin. In the new water assist version of this type of process, a plastic tube has replaced the foam core and is held under water pressure in the compression mould during carbon fibre braiding application from a braiding machine installed at BMW Landshut. The water is removed only after the resin has cured in a HP-RTM compression mould sufficiently to remove the part without deformation.

As the water is exposed to the typically high temperature arising in the HP-RTM process, a combination of pure, demineralised water and particular metal alloys ensures that no corrosion occurs. The curing process and therefore cycle time was minimised to an acceptable level for serial production by heating the water. Himmelstein says there was close cooperation with the press producer, toolmaker and epoxide resin supplier.