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Sunday, August 31, 2014

Next-Gen Fabrication and the Art of the Once-Impossible

Just about all companies in the business of machining and making components know that their shops’ capabilities are what make them valuable and stand out against competitors. But relatively few machining companies think out of the box and target unconventional applications that can bring additional revenues. One capability that was once considered for the lab but is now firmly in the real world of prototype and low-volume production is 3-D additive manufacturing, thanks to recent advances in speed, volume and part size.

Additive manufacturing, also known as 3-D printing, builds up parts in a layer-by-layer process that is guided by CAD data. The technique resembles ink-jet printing, in which powdered metal and a binder are deposited in a build chamber by a special print head that makes multiple passes, with each pass building up the part a bit more. The finished part can often feature a complexity that is often difficult, if not impossible, to produce by conventional machining.

One additive manufacturing supplier that is making advances is ExOne Co., based in North Huntingdon, Pa. ExOne develops machines that perform rapid fabrication of metal parts that are used in a variety of industries — automotive, aviation, defense, energy, medical and mining among them. At IMTS 2012 in September, ExOne unveiled its latest machine, the M-Flex 3D Printing System, which is said to achieve more than seven times the output capability of the company’s previous machines.

M-Flex produces “greater volumetric output per unit time,” says ExOne’s president and COO, David Burns. This means a build speed of 30 seconds per layer compared with 1.5 minutes per layer on previous models. The thickness of each layer is around 100 microns. The dimensions of the M-Flex’s build chamber are 400 by 250 by 250 mm (15.76 by 9.85 by 9.85 in), so designers can prototype or produce parts in a variety of sizes. Once a part is finished, it is autoclaved at 1,200 deg F to burn off binder material and initiate a mechanical bond between the metal particles. The ratio of binder to metal is usually “a couple percent,” Burns says. Binders are phenolic- or furan-based resins, and the company is working with undisclosed inorganic water-based materials.

The M-Flex is ExOne’s largest and fastest additive manufacturing machine.

Metal powder residue, meanwhile, is vacuumed up and recycled for the next part.

While powdered metals are the primary materials used in additive manufacturing byExOne machines, Burns says the company’s systems will eventually fabricate parts from tungsten, glass and ceramics. The company is also developing process technology for making sand castings, which will employ foundry sand (which is heavily composed of silica) and a furan-based binder. Layer thicknesses with the castings will run to 300 microns.

The 3-D printing machines aren’t inexpensive, ranging from $100,000 for a small unit to $1 million for one that is scaled for industrial production. The costs may seem daunting to some shops, but Burns says the process will fabricate any type of design — no matter how complex.

“We don’t care about design complexity,” he remarks bluntly. “The buy-in cost is fairly high, but it’s offset by what can be designed and made.”

Burns says that many designers often prefer an initial concept for a part but abandon it because the design cannot be made with conventional techniques. “When we unleash the design freedom of additive manufacturing, the value of the process skyrockets.” Since being involved with the technology, Burns notes that everything he learned about manufacturing “went out the window.” What he has discovered since, is that “complexity and simplicity cost the same”—in other words, a shop will not necessarily spend more money with additive manufacturing when the fabrication capability and the cost of not having it, including lost business, are considered.

Importantly, even the most complex designs can be produced relatively quickly, usually two working days or less, he adds.

ExOne President and COO David Burns shows a complex pipe forest for aerospace that was fabricated by the company’s additive manufacturing process.

ExOne’s process is being used for prototyping parts and also for special orders. Burns says the U.S. Navy, for example, used it to duplicate engine components during an overhaul of a submarine for which the original CAD data could not be located. A quote for castings of duplicate parts came with a timeline of 80 weeks for the design, development and production of the parts. With additive manufacturing, however, the parts were developed, produced and delivered in 10 weeks.

Companies are making rotors and stators for mining with ExOne’s process, as well as prosthetic components. One customer reportedly produces 3,000 small components per month for machinery.

Burns acknowledges that as an advanced technology, additive manufacturing comes with a learning curve, and ExOne is working to educate industry about its application and potential. ExOne has established five production service centers to support and train users, in Michigan, Pennsylvania, Texas, southern Germany and Japan, and seeks to add five or 10 more worldwide in the next two years.

ExOne licensed its technology, originally designed for metal and glass production, from the Massachusetts Institute of Technology and is working to integrate it within the industrial mainstream. An ongoing focus of development is making machines that produce larger parts faster and in greater volume. This not only increases the application potential of the process but improves return on investment.

“Our development keeps expanding,” Burns says, “and we’re not done yet.”




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