Powerful Parts

Tough materials, tight tolerances, low quantities, and complex shapes—leading suppliers offer advice for navigating the energy industry's stringent demands

America was founded on the world's first renewable energy source: wood. Sadly, the country's settlers soon found that the trees they burned to heat their homes and cook their food didn't grow fast enough to keep up with rising demand, so they switched to coal.

With the invention of electricity and then automobiles, however, coal's fossil fuel counterparts—oil and natural gas—soon took the lead in the energy parade and remain on top today. In fact, the 2022 Annual Energy Outlook report from the U.S. Energy Information Administration (EIA) forecasts that non-renewable energy sources will remain in the driver's seat through 2050.

It also noted that, with concerns over global warming and air pollution taking center stage, more earth-friendly alternatives such as solar, hydrogen, and wind power are gaining steam. Add to this a resurgence in nuclear energy and a push to upgrade existing hydroelectric sources with modern technology, and the writing is on the electric wall: Fossil fuels will eventually (although not likely in this baby boomer's lifetime) go the way of the prehistoric plants and animals that made them.

Whatever the energy source, gathering its photons, molecules, or movement, and then converting it into electricity is a demanding task. An offshore oil platform, for example, must operate in water hundreds or thousands of feet deep and drill holes in the earth many times this depth. The pressures are extreme, the fluids quite corrosive, and temperatures exceedingly high.

Because of this, oil wells and refineries use many of the same heat-resistant superalloys (HRSA) found in jet engines and other aircraft components. Metals such as Inconel 718 and 17-4 PH stainless contain relatively large amounts of chromium, molybdenum, nickel, and other alloying elements that make what would otherwise be ordinary steel extremely tough and strong—unfortunately, they also make these alloys difficult to machine and fabricate.

Scott Green cares little about machinability. As a principal solutions leader at 3D Systems Inc., Rock Hill, S.C., what he does care about is part count reduction, fuel efficiency, and time to market, attributes that allow direct-metal printing (DMP) to make significant inroads into the energy sector, most notably the industrial gas turbine (IGT) market.

Much of this success is due to DMP's ability to turn these high-performance metals into hugely complex shapes once impossible or at least cost-prohibitive to manufacture, eliminating some or all of the machining and assembly steps along the way. "There's a huge opportunity for microturbine use in decentralized power generation and storage, and that has significant implications for additive manufacturing," he said.

Look at what happened in Texas in the winter of 2021, he noted, when large chunks of the grid shut down due to inclement weather. Decentralized power generation would have avoided this. Then there's California, where owners of Tesla Powerwalls helped to alleviate brownouts by feeding electricity back into the grid. Such examples indicate that a modernized energy solution is one that includes small-scale, localized power generation is becoming more popular and will soon explode across the United States if not the entire planet.

Green contends that microturbines are a critical piece of this energy equation. When municipalities and county governments invest in their own power supplies, they suddenly become much less dependent on state and regional energy infrastructure and more resistant to weather- or civil-related disruptions.

What does 3D printing have to do with any of this? Good question, said Green. "Just as we’ve seen in other manufacturing sectors, DMP brings many benefits to the table. For starters, as we scale large industrial turbines down in size, opportunities for part consolidation increase. This simplifies the design and reduces cost. Manufacturers also enjoy greater design freedom, so are finding ways to improve fuel efficiency. Add to that the ability to iterate more rapidly and you can see why metal AM is playing an ever-more important role in the IGT industry's growth."

It's also helping to make existing energy infrastructure more earth friendly.

The appropriately named Green is working with engineers at a "major energy company" in its efforts to reduce and utilize waste gases through turbine technology. "Instead of venting it into the environment, they plan to redirect combustion by-products through a turbine, thereby capturing what is normally wasted heat while also removing carbon and other pollutants. It's called point-of-source flue gas redirection, and as with small-scale energy generation, 3D printing is making it a lot more attractive to energy producers."

Heath Houghton is a principal business consultant at San Francisco-based Autodesk Inc. He is seeing the same trend toward sustainability and the lowering of carbon footprints, and said that "pretty much every customer" he's engaged with over the past year has published goals along these lines. Energy efficiency is a key component of both, he noted, and an increasing number of manufacturers have turned to simulation and generative design in an effort to meet their corporate energy targets.

Many in the industry equate generative-design software with additive manufacturing. Houghton agrees this was one of the novel technology's first uses, but it's far from the last. "People are using generative to produce more efficient part designs, whatever the manufacturing method," he said. "At the end of the day, it all comes down to topology optimization, and that's effective for many applications, energy parts included."

As with 3D Systems’ Green and others interviewed for this article, Houghton is seeing increased activity in the energy sector. Many of these parts are quite large, he added. Turbine housings and impellers, for example, are components that Green knows well. When too big to fit within a 3D printer's build chamber or when it makes more economic sense, these and similarly complex parts are often produced using the investment casting process.

Here again, 3D printing has begun to play an important role. Manufacturers can now avoid traditional lengthy patternmaking processes by using 3D Systems’ QuickCast and competing technologies, printing wax or resin-based patterns in a fraction of the time once required. Similarly, generative design software allows designers to make components of all kinds—energy and otherwise—stronger, lighter, and with less material. This generally means less machining is required, saving manufacturers time and money.

Yet Houghton is quick to point out that Autodesk brings much more to the manufacturing party than design and simulation software. For instance, the company's flagship Fusion 360 product supports the programming of CNC machine tools with up to five axes of simultaneous motion, as well as centralized data management, collaboration between the design and manufacturing teams, and a host of additional capabilities, 3D printing among them.

"As with any industry sector, energy has its own unique challenges," he said. "As I noted earlier, the parts are typically quite large, so there are not only significant opportunities for design optimization, but opportunities for streamlining the machining and fabrication processes as well. We help manufacturers improve in each of these areas."

Jeff Wallace, vice president of engineering and chief technology officer of DMG Mori Federal Services Inc., (DMG Mori Group's U.S. government sales and support unit) in Hoffman Estates, Illinois, also has a lot to say about streamlining. The company has developed a wide range of advanced CNC machinery, much of it designed to combine what were once separate machining steps and, for many parts, completing them in just one or two operations. Whether it's a multitasking lathe, turn-mill center, or five-axis machining center, capabilities like these bring enormous benefits to machine shops of all kinds, those making energy parts among them.

And because such machine tools are enormously complex, DMG Mori has also worked hard to make them as easy as possible to operate. This is accomplished in large part through "technology cycles" that the company says reduce programming time, assure proper program structure, and minimize errors. Wallace ticked off a handful of these cycles, including multi-threading, easy tool monitoring, machine vibration control, Interpolation turning, and others, some of which are now on their second iteration.

There's also gear making. DMG Mori's equipment and technology cycles support hobbing, skiving, milling, and grinding, operations that until recently were limited to specialty equipment. Granted, gears are found in everything from the icemaker in your refrigerator door to the transmission in the family car, but as Houghton pointed out, the gears used by the energy industry are typically much larger than the commodity parts just named, and therefore require large machinery (like that made by DMG Mori) to manufacture.

They’re also produced in lower quantities and, given the need for quick turnaround on MRO and replacement parts, with shorter lead-times besides.

The multifunctional CNC equipment provided by DMG Mori and a few other leading machine tool builders checks the boxes on all of these requirements.

"It's a huge boon for the industry if they can get away from hobbing machines and dedicated gear grinders," said Wallace. "There are a couple reasons for this. First off, if the work dries up for one of those machines, they sit idle, whereas a multitasker can be used to make pretty much anything that comes through the door. Secondly, the delivery times on gear cutters, hobs, and skives is usually measured in weeks or even months, so if you don't have the right tool on hand, you’re going to be waiting a long time to make that gear."

Wallace cautions that multifunctional CNC machines aren't the be-all, end-all solution for certain applications. For high-volume manufacturing where part numbers are limited, a dedicated piece of gear-making equipment remains the most cost-effective solution, albeit a less flexible one. The same can be said for gears that demand extreme accuracy and fine surface finishes, although this statement is less true than it once was. "We grind on a lot of our platforms, and also have a dedicated grinding group called Taiyo Koki, so can often compete in this arena as well."

So can Sandvik Coromant US of Mebane, N.C., which offers a variety of high-speed steel, solid carbide, and indexable gear cutters that address a specific need in the gear-making industry: skiving. "Because five-axis machine tools have now become accurate enough to keep the main spindle and tool spindle perfectly synchronized with no lag or mismatch, they’re now able to power skiv, an advanced process used to make internal and external splines and gears."

That's according to Chuck Kirts, SAA sales and application specialist for gear milling at Sandvik Coromant. He points out that skiving and other forms of gear generation on machining centers are harder sells to customers doing automotive quantities with dedicated gear-cutting machinery. But for automotive customers and suppliers starting new production lines or replacing older lines, these machines offer an affordable and reliable option.The ability to do the skiving on the same machine you mill, drill, and turn is a huge plus. In the aerospace and energy markets where quantities are lower, it's a clear path forward, especially with the tough metals listed earlier.

"I recently worked with a company down south making parts roughly 10 feet in diameter on one of DMG Mori's larger machines," said Kirts. "We used one of our indexable CoroMill 180 Skiving Cutters to generate the gear profile, and because they had the correct technology cycle and direct drive, high accuracy spindles, they were quite successful."

Gears, turbine housings, stator rings—there's far more to the energy industry and the parts it produces than these few examples. Consider wind turbines. Yes, these use some of the same components and share a few similarities with other energy-producing equipment, but where a coal-fired plant burns hunks of carbon to generate electricity and a nuclear power plant splits uranium atoms apart in a continuous, carefully controlled explosion, wind turbine farms do nothing more than turn gently in the breeze.

Guy Dorrell knows all about it. A member of the global external communications team at Vizcaya, Spain-based Siemens Gamesa Renewable Energy SA, he's one of wind energy's biggest fans, and is especially intrigued with the manufacturing process behind the most visible component of any turbine—its blades. "They’re the largest single cast structure in the world, bigger than artillery barrels, tank hulls, you name it. Nothing else compares."

For those of you who’ve driven past an offshore wind farm and asked yourself how those blades are made, you might be surprised at the answer. There's no massive machinery here, Dorrell explained, nor robots crawling up and down the blade's 100-meter or more length, only a team of skilled craftspeople constructing each blade by hand. They set down individual sections of fiberglass and carbon-fiber sheet into a mold with resin between each one, smooth everything out with rollers, then flip it over and repeat the process on the other half. When done, the whole thing is placed in an oven for about a week. The blade is then sanded, inspected, painted, transported to the job site offshore, and bolted to the nacelle. "It's the most awesome, unbelievable thing you can imagine."

When asked why Siemens Gamesa hasn't followed in the aircraft industry's footsteps and automated the process, his explanation was simple. "It simply can't be done," he said. "The blades are tapered and have a very complex airfoil shape with really intricate internal structures to keep them from flying apart in 100 mph winds. We also balance the blades and then match them with others that will work together to dampen any harmonic effects. Believe me, we’ve looked at ways to mechanize it, but so far, the technology doesn't exist."

As noted, Dorrell is proud of the craftspeople and everything the company does. He said that 10 years ago, Siemens Gamesa was installing offshore wind turbines with 2.3 megawatts of generating capacity. Six generations later, that value has risen to 14 megawatts—enough energy to power a home with each rotation of the massive blades. It's the future that has him most excited though—the company is currently testing ways to produce hydrogen from seawater, an energy source that he said will be "completely benign" for the environment.

Until that day, Dorrell continues to hail the praises of wind energy. Where fossil fuels require energy producers to continually reinvest as wells run dry and they are forced to find new supplies, wind is the gift that keeps giving.

"The manufacturing is admittedly a bit difficult, as is sticking them in the water, but once you’ve paid for the investment, it's all gravy," Dorrell said.

"With a little routine maintenance, they keep spinning and spinning for several decades. And thanks to some new technology that we’ve developed, we can now recycle the blades and reuse the materials rather than burying everything in a landfill as has been the case. It's truly a green energy source, and will only continue to improve as the years go by."

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