Beyond Newsletters: Futuristic Printers Can Build Jet Engines

Almonst anyone can create greeting cards and art with a computer and an ink-jet printer. But some added technology and imagination can take printing far beyond ink and paper.

New printers based on ink-jet technology are revolutionizing manufacturing by turning out items as disparate as jet engine parts, precision-dose pills, and accessories for dolls, all from the desktop.

Scientists at the Massachusetts Institute of Technology in Cambridge, Mass., have created a versatile manufacturing process that can create custom metal, ceramic, and polymer parts directly from a computer model. Three-dimensional printing, as it is known, builds solid objects in layers using a device similar in concept and sometimes in size to a computer ink-jet printer. The result is solid objects that are either difficult or impossible to make conventionally, such as engine components with serpentine cooling passages.

"This technology makes parts you couldn't make any other way," says Emanuel Sachs, professor of mechanical engineering at MIT, who co-invented 3-D printing with MIT professor Michael Cima.

The process requires people to think of printing much more broadly, in three dimensions rather than two. Instead of applying ink to paper, 3-D printers selectively deposit a liquid material onto a thin layer of powder, causing the powder to bind and harden where the object is to be formed. The process is repeated, layer after layer, until the desired object is completed.

Although 3-D print head cartridges now under development have as many as several hundred jets, the heads potentially could have thousands of jets (the typical computer ink-jet printer cartridge has 52 jets). This means dots of binder could be positioned precisely to make objects with complicated geometries, cooling channels, or tiny microstructures. And different binder materials and powders can be used to form ceramic or biological materials.

MIT received its first patent on 3-D printing in 1993. So far, the university has licensed the technology to five companies, which are making different-sized printers for a variety of uses. A consortium including Boeing, United Technologies, and toymaker Hasbro is collaborating with MIT. And there are a couple of commercial 3-D printers for casting and rapid prototyping. But the more futuristic applications in medicine and aerospace still are experimental.

One of the most dramatic impacts of the new technology is in tooling - part of the production process to fine-tune casts to make an object. Currently, it can take weeks or months, and tens of thousands of dollars, to tool metal castings. A 3-D printer - making objects from a computer-aided design program - can do the same job in a week without tooling for a few thousand dollars.

That makes a big difference to companies wanting to be first to market with a new product. "One of the key differentiators in getting to market quickly is the time it takes for tooling," says Ralph Resnick, director of R&D at Extrude Hone Corp., an Irwin, Pa., licensee of MIT's technology.

Although 3-D printing is just beginning to nudge its way into the manufacturing world, those who are aware of the technology are excited about its potential.

"This is next-generation manufacturing," says Yehoram Uzeil, president of Soligen Technologies Inc., a Northridge, Calif., company using 3-D printing for metal casting. Soligen was the first to license the MIT technology.

THE technology also lets engineers and designers create product components from scratch rather than merely add incremental improvements to an existing component, says Ken Dreitlein, manager of program development at United Technologies Research Center in East Hartford, Conn. The center is examining 3-D printing to make jet-engine components.

Mr. Dreitlein is especially interested in an emerging use of 3-D printers to make functionally graded materials, new materials created by selectively depositing different binders onto one or more layers of powder. With conventional casting, only one material can be used. Functionally graded materials hold promise for making even stronger components, and potentially lighter and more fuel-efficient engines.

For example, blades and vanes - key components of a jet turbine's rotary engine - endure blasts of 3,000-degree Fahrenheit air. Vanes channel the air, and blades extract energy from it to turn the compressor and fan.

Current blades and vanes are made of tough super alloy metal. A 3-D printer could fashion more efficient cooling channels within the blades and deposit strengthening materials at key points in their structure. The goal is to make the blades and vanes able to stand higher temperatures so less fuel is burned more efficiently.

"We're trying to see if we can get a slight temperature increase from super alloys, but there are limitations," Dreitlein says. "If we can fabricate the blades and vanes differently using 3-D printing, we could make objects with cooling passages where you couldn't otherwise have them. And eventually you will be able to almost put atoms where you want to put them."