Cutting Tool Engineering
September 2012 / Volume 64 / Issue 9

Fueling improvements

By Kip Hanson, Contributing Editor

Using continuous improvement to reach automotive fuel-economy goals.

Today’s passenger cars, on average, generate more horsepower and consume less fuel than ever before. There are some obvious drivers behind this, such as high fuel costs, worry over dependence on foreign oil and environmental concerns. To make autos even more efficient, the U.S. government reached an agreement in 2011 with 13 automakers to begin delivery of 54.5-average-mpg vehicles by 2025, up from 27.8 mpg in 2011.

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Courtesy of Steel Market Development Institute

A forged steel output flange mounted on an aluminum-body automatic transmission.

According to the feds, that agreement will potentially save a total of $1.7 trillion in gasoline costs from 2011 to 2025. But how automakers will achieve that goal remains an open question. And what does the agreement mean to part manufacturers—the folks who make a living machining parts for these newfangled cars and light trucks? There’s no easy answer, but one thing is certain—change will continue to be the norm in the automotive world.

Lighter and Stronger

No one disputes the fact that better fuel economy starts with lighter vehicles. It should be a no-brainer, then, to eliminate steel wherever possible in favor of lighter materials, such as aluminum, magnesium and even plastic, right?

Not so fast, said David Anderson, senior director, automotive technical panel and long products program at the Steel Market Development Institute, Southfield, Mich. Anderson explained that steelmakers can produce product that competes on a pound-per-pound basis with aluminum. “One of the programs we recently completed was on a lower control arm,” he said. “The steel control arm matched the weight of an aluminum one, and we were able to produce it at a 35 percent cost savings.”

Anderson cited other programs with similar results, including body enclosures and chassis components.

“We’re seeing 25 to 35 percent weight savings at no additional cost to the OEM,” he said. “There’s a lot of development work going on, especially in the power train: axle shafts, transmission gears and connecting rods. Advanced high-strength steels have multiphase microstructures that help improve elongation and strength at the same time. But you have to consider all of the material’s attributes—its strength and machining costs, as well as the weight. It’s all about power density, which means getting more power from smaller components.”

Modern steelmaking provides lower inclusion content than previous methods and controls the inclusions that do exist so they don’t adversely affect part performance, according to Anderson. But how do inclusions—undesirable defects in metal—affect fuel economy?

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Courtesy of Makino

Robotic handling systems for auto parts, such as this one from Makino, offer greater flexibility than dedicated transfer lines.

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Courtesy of Steel Market Development Institute

Steel crankshafts, such as this one, offer greater strength than those made of iron.

“Because you’re improving the material properties, you’re able to do more with less material,” he said. “Consider a traditional cast iron crankshaft, like in the Ford V-8 engine. When they went to the V-6 EcoBoost in the F-150 [pickup], they used a steel crankshaft. This is because of the toughness that steel offers and the fatigue and durability performance—they’re now able to give you the same performance on a V-6 as what you had on the V-8, and better fuel economy too.”

Cutting these new steels can be difficult, but the steel industry is addressing it. “We’ve made extensive machining calculations and developed machinability databases to give automakers a feel for the cost impact of new steels,” Anderson said. “We’re also working with cutting tool manufacturers to improve machinability. Automakers need affordable lightweighting, and even though there may be a negative impact on machining costs with these new steels, you end up buying, and machining, less material. Overall, it’s a wash.”

Matt Zalusec, materials group leader for the United States Council for Automotive Research (USCAR), Southfield, Mich., agreed that steel is often the best choice for automotive components. “I anticipate continued progress and use of quenched and tempered steels for driveshafts and halfshafts. We’re using more hardened steels overall, and you’re going to see a lot of the 4000-series high-hardened and deep-hardened steels used for splines and gears. Steel technology is the driver for higher performance in driveline products.”

There’s more to driveline performance than good steel, however. Improved process control is equally important. For example, “At the end of the halfshaft, you have a highly complex gear tooth,” Zalusec said. “That inserts into a mating gear set, which in turn drives the wheel. Continuous improvement comes about through an accurate interface between the two—you cut down on wear with a good marriage between the surfaces and by providing a better lubricating film. If your gear sets aren’t perfectly matched, you get noise, vibration and harshness, or NVH. More and more, we’re trying to figure out how we can make the splines and gears more accurately through better process control and avoid NVH.”

The Alternative

But steel’s not the whole story at USCAR. Zalusec is a contributing member of the United States Advanced Materials Partnership Program (USAMP) on behalf of Ford Motor Co. “We co-collaborate on precompetitive technologies that benefit the automotive industry as a whole,” he said.

Part of this collaboration is research into alternative materials. “As far as the drivetrain goes, you might see couplers and universal joints made from aluminum in the future,” Zalusec said. “And thermoplastic covers and housings will continue to evolve. It’s just a matter of making sure these alternative materials meet the durability, reliability and environmental attributes we need.”

There’s also a potential for use of carbon fiber-reinforced composites. The biggest roadblock to increased CFRC use is cost—carbon fiber alone runs upwards of $9 to $10 per pound. “When you add in the resin and material processing needed to turn it into a usable product, the cost of CFRC runs about 10 times higher than steel,” Zalusec said. “Cutting that in half would be a great target. That doesn’t mean it becomes the material of choice, but carbon fiber, with its high tensile strength and modulus of elasticity, offers a lot of technical merit.”

Carbon fiber sounds cool—after all, high-end sports cars using this stuff are the envy of car enthusiasts everywhere—but is it really practical for vehicles used more for grocery shopping than impressing your friends at the car rally? “The reason people use carbon fiber isn’t so much its strength as its weight,” Zalusec said. “Reducing weight is a good thing, but when you reduce the weight of rotating components—such as carbon fiber driveshafts and brake rotors—you get a bonus. Because the engine now has to put out less horsepower to move a lighter rotational mass, you not only reduce the weight of the vehicle, but can use a smaller (and lighter) engine to power it.”

Does this mean everyone should rush out and buy waterjet machines and special carbon-fiber machining centers? “Not at all,” laughed Zalusec. “Extensive use of carbon fiber in automobile components is still years away.”

Your Father’s Aluminum

There’s no single material solution, however, when it comes to lighter vehicles and improved fuel efficiency. Doug Richman of Kaiser Aluminum Corp., Foothill Ranch, Calif., is the Aluminum Association’s Aluminum in Transportation Group technical committee chairman. Despite his obvious allegiance to aluminum, Richman keeps an open mind.

“I’m in awe of what the steel folks have done when it comes to developing new materials,” he said. He noted that multiple materials will continue to be used in vehicles. “The vehicles of the future will have the best of what all of us can put together, and aluminum will coexist with the advanced steels to make better cars.”

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Courtesy of Makino

Automated loading of engine blocks into a pair of Makino a61 horizontal machining centers.

Richman said the next big story with aluminum will be in automobile bodies because the material is dominant and approaching saturation in the power train area.

“We’re seeing a lot of growth in the sheet market: hoods, trunks, doors and the main body structures,” he said, noting that more than 80 percent of all engine blocks today are aluminum, aluminum cylinder heads have a 98 percent market share and transmission cases have long been made from aluminum. “Sure, there are new uses ramping up, such as turbocharger housings and valve train components, but the big aluminum revolution has come and gone.”

Still, Richman said: “Metallurgists are constantly, and even aggressively, trying to improve the fundamental properties of aluminum. And they’ve been quite successful—just look at aerospace aluminums. They’re twice the strength as those used in automotive, but they’re also far more expensive and more costly to machine. As a result, they don’t meet the value proposition needed for mass production of automobiles. Most automotive aluminum grades used today have been in the market for more than 50 years.”

Richman noted the real improvements in automotive aluminum have been made in its production, not the material itself. “Even though the material is the same, the casting process has improved substantially over the past 25 years,” he said. “We now enjoy remarkable levels of structural integrity, with consistent, high-integrity castings.” This is accomplished largely through process control along with a greater understanding of metallurgy and better modeling software.

Dick Schultz, managing director for consulting firm Ducker Worldwide LLC, Troy, Mich., agreed that aluminum is used in the lion’s share of engine components. “If you look at the typical power train, it has an aluminum engine block and cylinder heads. Big heavy trucks are still using cast iron blocks because they use diesel engines, which have high torque and twice the compression of a gas engine. But we think the aluminum industry will eventually develop ways to cast alloys that can take the extra stress of a diesel.”

However, aluminum might be losing its grip in some areas. “We’re seeing a gradual shift to reinforced nylon use in intake manifolds,” Schultz said. “It’s probably 50/50 now, and nylon gains an additional one to two points of market share each year. It’s like the old battle between steel and polymer gas tanks. Ultimately, polymers—for something that doesn’t require a lot of strength—provide shape flexibility and lighter weight. In the end, it comes down to cost.”

Better Mousetraps

The automotive industry has to do more than make lighter products to achieve 54.5 mpg. One area that’s receiving a lot of attention is the transmission. For example, automotive supplier Dana Holding Corp., Maumee, Ohio, has developed a multilayer steel separator plate targeted at 7- and 8-speed automatic transmissions.

“We’re able to eliminate the traditional paper gaskets used to seal the valve body entirely,” said Dana’s Engineering Manager David Nash. “By joining three relatively thin layers of stainless steel, we can generate sealing pressures roughly four times that achieved with paper gaskets. So you avoid the paper contamination and leakage problems seen with traditional gaskets, while the higher sealing pressure allows the transmission to work at higher pressure with higher flow rates, increasing efficiency.” This means you can use a smaller pump to do more work and further reduce vehicle weight.

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Courtesy of Methods Machine Tools

Front-loading a Nakamura CNC lathe in a Methods JobShop Cell.

Nash, too, sees a shift to alternative materials. “Everyone is focused on weight reduction,” he said. “We’re doing a lot with plastic. Valve covers, for example, which have long been made of cast aluminum, are moving to glass-filled nylon and even recycled, post-consumer plastic. We’re doing the same thing with oil pans.”

There’s also a focus on better thermal management of the engine. “By actively warming the engine, we can reduce cold-start emissions and improve fuel economy,” Nash said. “And, with the increased use of turbochargers and the fact that small engines simply have to work harder to produce the same or more power from a smaller package, we’re seeing engine temperatures up to 300° F, with maybe 350° F in the near future. Managing temperatures this high will be an engineering challenge we are excited about meeting.”

Making Parts

How are machine shops and equipment builders coping with all of this automotive change? Very well, thank you. Mark Rentschler, marketing manager for machine tool builder Makino Inc., Mason, Ohio, said the industry is seeing changes to part designs because of lightweighting, but at the end of the day, “It’s still about making parts. You just need to do it more efficiently. Tolerances are getting tighter, particularly in critical boring operations seen in transmission housings and brake valve bodies. And quality requirements are increasing. OEMs don’t want 99.997 percent Cpk anymore—they want perfection. They expect good parts now and good parts 5 years from now. To do that, you must have stable, productive processes.”

One piece of the perfect-process puzzle is flexible automation. Traditionally, high-volume automotive machining meant dedicated transfer lines and specialized equipment. That theory seems to be going the way of the Edsel.

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Courtesy of Methods Machine Tools

A robot’s end-of-arm tooling grips aluminum blanks in preparation for a turning operation.

“Even in high-volume work, part manufacturers need the flexibility to accommodate small design changes and varying volumes,” Rentschler said. “You might run four or five different programs through one machining cell, each having its own variable forecast over the course of a 5-year contract. You can’t easily do that with a transfer line.”

Another machine tool supplier seeing big increases in automation is Methods Machine Tools Inc. According to Thomas Saur, general manager of the Michigan office for Sudbury, Mass.-based Methods, use of robotic handling systems has increased dramatically. “About 70 to 80 percent of the turnkey systems we sell today are automated,” he said.

Saur explained that automotive suppliers are looking for relatively simple, low-cost machines that can be placed in a cellular configuration. “We’re seeing this across vertical machining centers and lathes with robotic handling systems, as well as horizontals using linear pallet systems.” Better yet, automated machines require less labor to operate, so part manufacturers can avoid sending work to low-labor-cost countries like Mexico, China and Poland. “Automation allows more machining work in the U.S.,” Saur said.

As auto parts get smaller, lighter and more challenging to produce, will part manufacturers hit the wall with conventional machining processes? That day is a long ways off, but designers and researchers are already looking for new ways to push the limits of manufacturing.

Richard Pierce, president and CEO of laser machine builder Raydiance Inc., Petaluma, Calif., said his company is interested in creating a new form of precision. Raydiance has been closely involved with the Department of Energy and Delphi Automotive Systems in the development of next-generation gasoline direct-injection fuel injectors, or GDi.

Pierce said: “There’s been a huge R&D effort in fuel injectors. Our lasers drill 90µm to 200µm holes in GDi nozzles, and there’s a demand for even smaller holes in diesel injectors. There are no limits to what you can do with this light. We’re just on the cusp of learning what this technology can do.”

Kaiser Aluminum’s Richman may have said it best: “Nothing’s standing still in this game. Since Henry Ford put his first automobile on the road, manufacturing has been challenged to improve. And it has. Horsepower then was rated in the single digits per liter [of gasoline], while today we’re seeing over 100 hp per liter. It’s been a straight line of continuous improvement. And you really have to credit the automotive industry, the material suppliers and the tier-level suppliers for this. Everyone is doing a marvelous job.” CTE

About the Author: Kip Hanson is a contributing editor for CTE. Contact him at (520) 548-7328 or khanson@jwr.com.


Contributors

Dana Holding Corp.
(419) 887-3000
www.dana.com

Ducker Worldwide LLC
(800) 929-0086
www.ducker.com

Kaiser Aluminum Corp.
(949) 614-1740
www.kaiseraluminum.com

Makino Inc.
(800) 552-3288
www.makino.com

Methods Machine Tools Inc.
(877) MMT-4CNC
www.methodsmachine.com

Raydiance Inc.
(707) 559-2100
www.raydiance.com

Steel Market Development Institute
(248) 945-4777
www.autosteel.org

United States Council for Automotive Research
(248) 223-9000
www.uscar.org

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