How to Build a Jet Engine? Press ‘Print’ Button

EAST HARTFORD, Conn. (The Hartford Courant/MCT) —

For decades, aerospace manufacturers like Pratt & Whitney have fabricated engine parts by tooling, lathing, milling and forging.

Now, they’re printing.

Unlike that laser printer in your office, there is no toner, no paper and no “PC Load Letter” errors.

Instead of ink, these printers – called 3-D printers – use lasers to heat granules of plastic or metal to build up three-dimensional parts, layer by layer. The end product could be any solid design, however complex.

Aerospace manufacturers like Pratt & Whitney and GE Aviation are extending the limits of this technology to make production-run parts for their latest commercial engines. This process is letting manufacturers design components that would have been impossible to mill or forge in yesterday’s aerospace factories, while saving money and, in some cases, making parts lighter.

And for 3-D printing – also called additive manufacturing – the fact that the vanguard technology has passed through the testing fires of a jet engine is a good sign.

Tom Maloney, director of technology research and applications for the Connecticut Center for Advanced Technology, which aids manufacturers who want to use the technology, said, “It’s definitely progress … even call it a milestone.

“We’ve learned a lot about how we should run these machines,” he said of 3-D printers. “I’m certainly very bullish that we’ll see much more additive technology implemented in this country, but we are also going to see other manufacturing equipment and software continuing to evolve as well.”

Pratt, the engine division of Hartford, Conn.-based United Technologies Corp., put more than two dozen 3-D-printed components on its latest quiet and fuel-efficient PurePower geared turbofan engine, said Thomas Prete, the company’s head of engineering. “We’ve contemplated lots of parts, and continue to add to the list.”

Pratt’s main competitor, GE Aviation, is using 3-D printing to make complex fuel nozzles for an engine.

Prete said that Pratt’s designers can now make a single part in one process that otherwise would have been a time-consuming combination of five or 10 pieces that need to be attached and heat-treated before they are ready. That improvement alone saves time and money.

But the main advantage, Prete said, is that engine designers can do things that would have been impossible. “In a basic fabrication,” he said, “you sometimes have to make performance trades.” For example, engineers can make an initial design that’s an A-plus, but because of manufacturing limitations, sometimes only a B-minus is possible.

With the technology, it’s just as easy to make something complex as it is to make something simple. It’s like firing up the inkjet to print out a copy of a famous painting compared to using it to print a solid color. It doesn’t take more time or more ink to print out the one that is significantly more complex.

And to the military, a wide, practical view of the technology is the ability to print replacement parts, supplies and perhaps even structures for military bases with just a machine and a supply of material, whether plastic or metal. That ability could transform an aircraft carrier into a “floating factory” that could supply replacement parts to a broken tank or an aircraft by processing a data file through an onboard 3-D printer.

Notwithstanding the new wave of interest, with news of plastic firearms and cranial implants printed from computer files, the 3-D printing narrative at Pratt began in 1988, when the company bought a fleet of 3-D printers for its engineers to design prototype engine parts.

The machines spat out plastic prototypes for testing and development and, once they were deemed to be of optimal design, engineers milled or forged a metal version. In the past four or five years, as technology has advanced, Pratt adopted metal 3-D printing prototyping.

“What we do now is go directly from design to metal using additive manufacturing, so you eliminate an entire process,” Prete said. The process speeds up the company’s engine development and saves costs by eliminating the need to mill down new parts every few days.

“What’s new here is additive manufacturing of this type is replacing traditional types of subtractive manufacturing,” Prete said.

Pratt wouldn’t reveal which specific parts were being printed, because the information is proprietary. But Prete said that some of the 25 parts are simple, such as brackets, and others are more complicated components in the engine’s air pathway, a high-temperature and constant-stress area of the engine.

Industrializing the technology to the point that it will withstand the jet engine environment – building confidence in part strength and performance – has been quite the process, experts say. Materials and processes must be unimpeachable and consistent. Costs need to make sense economically, and output needs to keep up with traditional manufacturing methods.

For Pratt, 3-D printing parts at production speed is the next big step. The company is determining how many machines it needs, how they need to be arranged and how to get to optimal output. “It’s a normal industrial engineering discussion at this point,” Prete said.

In November, GE Aviation acquired a Cincinnati-based 3-D printing firm, Morris Technologies, and its sister company, Rapid Quality Manufacturing. Months ago, GE announced that it would be 3-D printing the fuel nozzles on its commercial LEAP engine, being developed with French aircraft manufacturer Snecma. When the parts were manufactured traditionally, they were made of 18 parts fused together. Now they are made as one part and come out 18 percent lighter.

GE spokesman Rick Kennedy said the company is splitting the acquired 3-D printing operations into two streams, similar to what Pratt has done. Half is focused on preparing the shop floor for production operations, and the other half looking at what other engine parts can be 3-D printed.

Additive manufacturing and subtractive manufacturing are the yin and yang of making things. Think of additive like building something with Lego blocks: You put small pieces together to make something larger. Subtractive manufacturing, which includes milling and lathing, is more like sculpting: You start with a block or marble, and chip and shave away until a statue, or engine part, emerges.

Much of manufacturing currently falls in this second category, but that’s changing. In 2012, the 3-D printing industry expanded 28.6 percent, to a $2.2 billion slice of the economy, according to an analysis released in May by Wohler Associates, a technical consulting firm based in Fort Collins, Colo. By 2021, the firm expects the industry to be worth $10.1 billion.

In the next five years, GE plans to invest $3.5 billion in additive manufacturing and 3-D printing.

More than anything else, though, the placing of these components into jet engines is just what the advanced manufacturing industry has been waiting for: a serious proving ground that shows that mainstream manufacturers have figured out how to make the materials and the process work, and work in a quality way that makes financial sense.

It’s one thing to print a plastic trinket, but it’s another thing altogether to manufacture a metal component that will hold up under thousands of degrees of temperature, constant stress and years of operation.

“A lot of people talk about additive manufacturing – we call them the hype people – they’re the ones that make a lot of the desk trinkets,” Prete said. “The magic comes from being able to predict accurately the capability of the materials using the additive manufacturing process, and being able to confidently put it in a jet engine environment.”

Experts say that the technology is finding a way into big industrial applications now because of a confluence of research into metals and materials for 3-D printing, as well as explosive growth in supercomputing power.

“One of the things that’s really propelled the technology is computing speed,” said Dave Hudson, president of Joining Technologies, an East Granby, Conn. additive manufacturing firm that specializes in laser cladding, another form of additive manufacturing. “The mathematical algorithms and calculations would be impossible without today’s supercomputers.”

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