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How Practical is 3-D Metal Printing? OPEN ACCESS

3-D Printing is Rapidly Establishing Itself in Aerospace, Medicine, and Dental Implants. Is it Ready to Go to Work in More Cost-Sensitive Industries Like Consumer Products or Power Systems?

[+] Author Notes

Paul Sharke is a technology writer based in Little Silver, N.J.

Mechanical Engineering 139(10), 44-49 (Oct 01, 2017) (6 pages) Paper No: ME-17-OCT3; doi: 10.1115/1.2017-Oct-3

This article explores the application of 3D printing technology in cost-sensitive industries such as consumer products and power systems. Metal printing offers advantages such as the ability to reduce parts count, assembly time, and weight while creating complex internal and external geometries that could not be made any other way to manufacturers in almost every industry. 3D design also makes it possible to customize medical and dental implants for each patient. Industrial product designer Keith Handy used the flexibility of 3D printing to redesign the system. Instead of putting the device above the chain, he built a tunnel-like part that the chain could pass through. Euro-K, a Berlin-based firm that develops small energy converters, created a burner that could do both. 3D printing enabled Euro-K to optimize the burner’s geometry to handle gaseous fuels and difficult-to-burn liquids like fuel oils, a byproduct of alcohol distillation, while reducing size. The article concludes that as new competitors enter the 3D printing arena, systems will grow better, faster, and less expensive. In addition, most important of all, engineers will be standing by with lots of new and surprising ways to take advantage of 3D metal technology

Now that the fundamental patents for many 3-D metal printing technologies have expired, the field is undergoing a rapid increase in competitors, innovations, and interest. Yet search for everyday examples of 3-D metal printing and you are likely find example after example of aerospace, medical, and dental applications.

So, the question is: What does 3-D metal printing offer rank-and-file engineers who are not working with these popular applications?

The answer, according to Greg Thompson, global product manager of 3-D printing at Minneapolis-based Proto Labs, is a resounding, “Plenty.”

“If something is hard to make, it's a good candidate for DMLS,” he said. “If something is impossible to make, it's a great candidate.”

Metal printing offers advantages to manufacturers in almost every industry, Thompson argues. Many are well-known to anyone with even a passing familiarity with the technology. They include the ability to reduce parts count, assembly time, and weight while creating complex internal and external geometries that could not be made any other way. These clearly benefit aerospace companies, where every ounce shaved off a part saves fuel over decades of flight.

Renishaw and Empire Cycles 3-D printed a bicycle frame in titanium. Right: They fabricated the entire assembly on a single build plate in one pass. Image: Courtesy of Renishaw

Grahic Jump LocationRenishaw and Empire Cycles 3-D printed a bicycle frame in titanium. Right: They fabricated the entire assembly on a single build plate in one pass. Image: Courtesy of Renishaw

3-D design also makes it possible to customize medical and dental implants for each patient.

Aerospace, medical, and dental are what retailers call “the carriage trade,” industries where margins are high and manufacturing costs are often a secondary consideration. These industries can afford 3-D metal printing because they already charge a premium price for their products.

For more price-sensitive industries, 3-D printing is a harder sell.

While it may never achieve the high volume and low piece cost of traditional manufacturing, it has the potential to deliver value in ways that are not always considered by conventional means of estimating product costs, Thompson said. For example, 3-D printing can unlock new product development processes, he said. By slicing time needed to create functional prototypes, it helps companies rapidly bring products to market, respond to customer feedback, and improve their designs. It also helps companies do this without investing in full production.

3-D metal printing can simplify supply chains. By consolidating parts into a single structure, engineers can whittle away at component manufacturing, sourcing, and assembly expenses. Consolidation may also eliminate failure points in assemblies, improving reliability and reducing warranty costs.

Optisys, a Grapevine, Texas, company that makes military and aerospace microantennas, did just that with a demonstration directional tracking antenna array that consolidated 100 discrete parts into a single, palm-sized 3-D printed assembly. The design shaved weight by 95 percent and cut production costs by 20-25 percent.

The array was an outlier. 3-D parts will nearly always cost more than their conventionally machined equivalents. Yet soft cost savings may make them competitive.

Finally, 3-D metal printing gives engineers nearly unlimited freedom to improve products, since it can create parts that are impossible to manufacture by any other technology. This allows engineers to go far beyond a part's existing architecture to create something better that may look nothing like the piece it replaces.

One industrial-strength example is VTT Technical Research Center of Finland's redesign of a hydraulic valve block with Nurmi Cylinders. The block controls the loads applied by fluid to cylinders in hydraulic systems. Manufacturers currently make blocks by drilling straight holes into a solid block of metal and connecting them by drilling cross channels.

This yields a system of passages connected at 90 degrees, some plugged at the ends to prevent leaking. The 90 degree turns reduce the efficiency of fluid flow by boosting pressure, which sometimes causes the plugs to leak.

A 3-D printed metal hydraulic block eliminates leaks caused by pressure buildup when fluid channels take 90-degree turns.

Photo: VTT Technical Research Center of Finland

Grahic Jump LocationA 3-D printed metal hydraulic block eliminates leaks caused by pressure buildup when fluid channels take 90-degree turns.Photo: VTT Technical Research Center of Finland

3-D printing eliminates the need for any cross channels. Instead, the engineers build more efficient channels with graceful bends and no plugged openings to leak. The resulting block is one-third the size of the original.

The VTT design looks like a win, yet Nurmi is not rushing its new design into production. It still takes a lot of work to bridge the gap between a CAD model, a 3-D prototype, and an affordable part that is ready for prime time. Which is why, for now, engineers have given 3-D printing a mixed reception.

Jamie White of Metier Velo in Salt Lake City overcame that hurdle when he set about to build a better custom bicycle.

Although he makes bikes, White thinks of himself as a service provider. His service is fitting a high-end carbon fiber bicycle frame to the dimensions of an individual rider.

His high-end bicycles use carbon composite frame tubes, whose low mass and greater stiffness transmit pedal power to the bike more efficiently than steel or aluminum.

But carbon has two disadvantages. First, carbon tubes are made in molds, and building a custom mold for each rider is uneconomical.

This is why many companies customize bikes by joining carbon tubes with either carbon composite lugs or fillet wrap. Second, while carbon tubes are strong, they crack rather than dent in accidents.

White solved both problems at once by opting for 3-D printed titanium lugs. The titanium lugs are strong and light. Unlike carbon fittings, they let him replace damaged tubes. It took White about one year to find a production partner that could make the lugs at a “doable” price.

It was worth the wait. Metier Velo's bikes look like nothing else on the road. They capture an Old-World aesthetic that reflects 100 years of metal bicycle engineering evolution. Riders can also customize their lug design, so every bicycle is truly customized.

Metier Velo's 3-D titanium lugs are strong, lightweight, and make it easy to replace broken carbon composite frame tubes.

Photo: Metier Velo

Grahic Jump LocationMetier Velo's 3-D titanium lugs are strong, lightweight, and make it easy to replace broken carbon composite frame tubes.Photo: Metier Velo

Metier Velo is not the only company 3-D printing high-end bicycle parts. Britain's Empire Cycles teamed with 3-D producer Renishaw to redesign an aluminum bicycle seat post bracket for 3-D titanium. Although titanium alloys weigh 30 percent more than aluminum, the redesigned bracket shaved 44 percent off the aluminum part's weight.

Empire and Renishaw did this by taking advantage of titanium's superior strength. They hollowed out some supports, and used Altair's solidThinking Inspire software to automatically remove material from the CAD model's non-load-bearing sections. This sliced weight to 200 g, from 360 g for aluminum.

The two companies then built an entire 3-D bike frame in sections, which they bonded together. The resulting bike is extremely rugged, but far too expensive for production. It cost $26,000, but Chris Williams, Empire's founder, says that the project opened his eyes to the flexibility and benefits 3-D metal brings to design.

Startups often turn to 3-D printing to launch new products without investing in conventional production. Yet even though they start with 3-D, they may end up elsewhere.

That is what happened to SolePower, a Pittsburgh startup that used 3-D printing to develop a shoe-based device that generates electrical power as the wearer walks. It could power lights, sensors, and communications and GPS systems for hikers, soldiers, or first responders working under hazardous conditions.

The kinetic generator is a mechanical device about the size of a deck of cards, SolePower project manager Davit Davitian explained. It relies on a gear train and series of links to turn vertical forces generated by walking into horizontal forces that turn the generator.

Kappius Components originally made key components of its bicycle hub with 3-D metal (black hub), but switched to electrical discharge machining (red hubs) when orders started to rise.

Photo: Kappius Components

Grahic Jump LocationKappius Components originally made key components of its bicycle hub with 3-D metal (black hub), but switched to electrical discharge machining (red hubs) when orders started to rise.Photo: Kappius Components

Davitian likens it to the gear train a in watch, only stout enough to withstand higher forces and millions of cycles.

His team used both plastic and metal printing to prototype the gear ratios, relying on the quick turnaround of 3-D printing to run through several iterations. They used the metal printed gears for treadmill and other trials, Davitian said.

Because the application applied high stresses to precision gears, 3-D metal parts did not offer the ideal material properties and surface finish for the application. Still, they enabled SolePower to move its technology forward.

“The links are now made with metal injection molding,” Davitian said, “but that's only because we found a good vendor in India. In the States, tooling would have cost us $15,000 per link.”

Nor did vendors want to deal with his small quantities. “3-D metal printing was the only practical and cost-efficient method for us to make the links during the four years of development,” Davitian said.

Brady Kappius, president of Kappius Components in Boulder, Co., had a similar experience. While earning his master's degree in mechanical engineering from the University of Colorado, Kappius and his father, Russ, a winner of six bicycling racing Masters titles, began designing a revolutionary drive system for mountain bicycles.

The Kappius hub is twice the diameter of standard hubs. Inside, the drive assembly consists of an outer drive ring, an inner ring with 60 teeth, and eight pawls that engage two at a time with the teeth on the inner ring. This gave the power train 240 points of engagement, compared to 18 to 36 in standard drives. It enables the rider to engage the gear 1.5 degrees, and transfer power to the wheels faster when racing or executing tight maneuvers.

It took only a few months to go from design to production, shipping 100 hubs their first year. Even while they were sending hubs to early adapters, they were modifying the design to keep ahead of competitors.

“3-D printing was a great resource,” Brady Kappius said. “When we were small, it let us make design changes and develop new models quickly.”

Yet 3-D production was unsustainable. It took two builds and 50 hours to print 10 sets of 10 outer rings and 80 pawls. Then Kappius had to remove the support struts on a CNC machine and heat treat the final parts to harden them.

As orders began to rise, they turned to an Asian manufacturer that could make the rings and pawls for less money using wire electrical discharge machining.

3-D metal parts are making headway in industry, especially when innovative designs can save time or money. Take, for example, the plastic chains of a bakery conveyor. They get clogged with crumbs and oil, and technicians must periodically shut down the line to replace them. Engineers tried cleaning the chains by shooting pressurized steam from a fixture above their track, but it took several passes and did not fully clean the links.

Industrial product designer Keith Handy used the flexibility of 3-D printing to redesign the system. Instead of putting the device above the chain, he built a tunnel-like part that the chain could pass through. As it did, 10 jets blasted it from different angles with 145 psi steam. Handy's first design removed 85 percent of the gunk. An improved redesign got it all.

The final part was less than 2 in. on a side. Handy integrated it into the line and has since sold the device to many bakeries.

“I did not have to worry about parting lines, assembly techniques, or post-finishing for this application,” he said. “In effect, I was designing something that was otherwise impossible to manufacture. It was like being back at college.”

The same type of innovation shows up in a micro-burner that can handle both gaseous and liquid fuels. While gaseous fuels mix easily with air before burning, combustors must pressurize and spray a fine mist of liquids into air before combustion.

Euro-K, a Berlin-based firm that develops small energy converters, created a burner that could do both. 3-D printing enabled Euro-K to optimize the burner's geometry to handle gaseous fuels and difficult-to-burn liquids like fusel oils, a byproduct of alcohol distillation, while reducing size.

Euro-K designed the new combustor for Bilfinger, which provides microturbines for factories and waste sites.

“We are able to guarantee our customers the freedom of choice in terms of fuel, and switching to other fuels after the plant has been purchased can be easily arranged,” said Frieder Neumann, Bilfinger's deputy head of micro-gas turbine development.

He also added that the technology is priced attractively. That is not always the case for 3-D printed parts. Clearly, many applications are simply uneconomical. Yet as Neumann's and Handy's experiences show, there are cases where innovative design unlocks a benefit that makes a larger product, in this case, a microturbine, more attractive.

That is going to be happening more and more often in the future. As new competitors enter the 3-D printing arena, systems will grow better, faster, and less expensive. And, most important of all, engineers will be standing by with lots of new and surprising ways to take advantage of 3-D metal technology.

A 3-D printed open manifold steams off flour and oil from bakery convey chains in a single pass. Photo: 3D Systems

Grahic Jump LocationA 3-D printed open manifold steams off flour and oil from bakery convey chains in a single pass. Photo: 3D Systems

Euro-K 3-D metal printed the complex geometry of a micro-burner that can handle both gaseous and liquid fuels. Photo: Euro-K

Grahic Jump LocationEuro-K 3-D metal printed the complex geometry of a micro-burner that can handle both gaseous and liquid fuels. Photo: Euro-K

Copyright © 2017 by ASME
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