Trexel Inc. issued a major green claim: Using MuCell to make auto components for a fleet of 100,000 cars can reduce the carbon footprint of a car by more than 6.3 million gallons of gasoline, along with carbon-dioxide reductions of nearly 65,000 metric tons, over the course of a car's lifespan of 150,000 miles, according to Trexel's estimates.
To get the numbers, Trexel, of Woburn, Mass., used specific mold trials and commercial applications for the MuCell microcellular foaming technology. Trexel hired environmental firm Simply Sustain LLC of Newark, Del., to determine MuCell's environmental impact using a cradle-to-grave analysis.
Until recently, most decisions to use the MuCell process were made on a piecemeal, part-by-part basis, said Trexel President and CEO Stephan Braig.
However, the industry is now recognizing the immense strategic potential that the MuCell process holds for reducing vehicle weight and costs.
For the study, Trexel reviewed 70 components, representing about 194 pounds of vehicle weight. MuCell cut that by 35.4 pounds per car, Trexel said.
Trexel also released details about two automotive applications in Europe: air-bag covers and engine-valve covers.
TRW Automotive Inc. used MuCell to injection mold air-bag covers on Volkswagen AG's Tiguan compact crossover vehicle that feature no sink marks, excellent dimensional stability and design freedom compared with traditional solid injection molding, according to Trexel.
MuCell also allowed Livonia, Mich.-based TRW to use smaller injection presses, with clamping forces of 300 tons, vs. 500-ton machines.
MuCell's foaming cell growth happens in the mold, which can replace the traditional pack phase, so the application may be designed for function not for traditional plastics processing. For example, ratios of rib-to-wall thickness can be optimized for performance, not just to eliminate sink marks.
Also, with conventional injection molding, you need a separate secondary operation to laser-cut the back side of the air-bag cover. MuCell makes it easier to mold in tear seam lines and a living hinge, by using variable wall thicknesses.
ElringKlinger AG of Dettingen, Germany, uses MuCell to mold two-piece nylon valve covers for VW's 1.6-liter and 2.0-liter diesel engines. Dimensional stability is key, because part flatness is critical. The German molder also could use smaller-tonnage presses.
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