BMW is using a newly developed water assist system to improve the strength, cut fiber costs and reduce the weight of carbon composite parts at its Landshut, Germany site. BMW is a global leader of parts made from carbon-reinforced plastic (CFRP) in the sixth generation of the 7 Series and other models.
The water-assist system was developed by Maximator GmbH of Nordhausen, Germany, a supplier of high-pressure equipment for several markets, including plastics processing.
“The Maximator water assist system is being used in conjunction with the HP-RTM (high-pressure resin transfer molding) procedure for the first time at BMW. We adapted our water assist technology especially for this process,” said René Himmelstein, vice president sales & marketing. “The fluid injection broadens the application range of the HP-RTM technology significantly and opens up new possibilities in terms of lightweight constructions.”
The production system at the BMW Group site in Landshut comprises two central units: the water treatment unit and the pressure unit. The water assist system generates internal pressure that is exerted onto a blow mold. Water is evacuated after the injected resin hardens around the carbon fiber matrix that is woven around the lost mold.
Himmelstein said that the high-pressure supply unit and the valve assembly needed to be fitted as close to each other as possible. This was achieved through use of a complex injector with multiple integrated monolithic valves and process technology for series production.
It’s necessary to use very pure, demineralized water at a very high temperature. All system parts that come into contact with water are made of proven metal alloys to ensure they can withstand this aggressive corrosion. A water heater was also installed to accelerate the resin hardening process
The parts need to be produced in a high cycle rate while ensuring that they have a certain temperature when taken from the mold so that they do not deform.