Aerospace Materials
now it’s a fi ber within a matrix. And that,” he said, “is what imparts the toughness to these materials.” “The beauty of what GE’s been able to develop is that we get very close to full density on these parts—maybe 98% density or more, without losing the properties of the fi ber,” he noted. The fi nal step in creating a CMC part is fi nishing it with
fi ve-axis CNC milling machines. The CMC material is extreme- ly hard and durable—too tough for traditional cutting tools, Wessels said. “Rather than conventional cutting tools, we have to use diamond-coated tools. They’re the one thing we have that cuts through this material effectively on a bulk scale. But other than the use of diamond-encrusted tools, the rest of the process is typical machining. We use the same kind of fi ve-axis programming that’s used throughout the industry.”
Size Matters The fi rst part to be manufactured at Asheville is a turbine shroud that’s about 5" (127-mm) in circumferential length,
but CMC components can be much larger and smaller. The pyrolysis and melt-infi ltration processes aren’t affected at smaller sizes, Wessels said, but he noted that “when going small, the handling of the plies becomes more complex.” At somewhat larger sizes, in contrast, the plies become easier to handle when laying up the part. “But when you get too large,” he noted, “you end up needing a lot of silicon to infi ltrate the part. “We’ve been able to make pretty large parts, though.
We’ve made a combustor liner from this material, a part that’s about 32" [813-mm] diam and with an axial length of 8–10" [203–254 mm].”
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Reliable shrinking – Fastest in the galaxy.
In the popular imagination, there is no intermediary step between the creation of a new material and its implementa- tion in mass production: In Hollywood terms, we expect a scene with a lab-coated scientist holding a smoky beaker and shouting “Eureka!” and a quick jump to footage of an assembly line or conveyor belt, if not straight to scenes of happy consumers. Manufacturers know better, of course. At GE Aviation, this is where the ‘microfactory’ and Jeff Wessels come in.
Shrinking Technology Tooling Technology Balancing Technology
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Measuring Instruments
“Our Global Research Center in Niskayuna, NY started developing this technology in the early to mid-1990s. They formulated the basic process and designed and made the necessary equipment. Around the early-2000s timeframe, that process was transitioned to our Newark, DE, microfactory site, where I’m at right now.” In 2006, Wessels, who has been with GE for 28 years, was tapped to start up GE’s fi rst microfactory, which was devoted to high-pressure turbine air foils. There, he worked on ways to provide lean practices to improve the manufacturing processes, he says, resulting in a signifi cant amount of cost reduction. “Two years ago, because of the mi- crofactory experience and my materials
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ManufacturingEngineeringMedia.com | February 2014
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