MTU America: Machining parts for large diesel engines

Eight machining centers steadily crank out parts in a former bearings factory that, today, is home to MTU America Inc. When the company moved its manufacturing operations from Detroit to the factory in Graniteville, S.C., in 2010, the area now occupied by MTU’s machining department had a dirt floor.

“We gutted it completely and put in all new infrastructure,” said Jeremy Diebel, senior manager of machining and apprenticeship coordinator for MTU.

The 320,000-sq.-ft. facility houses the only North American machine shop operated by MTU—the Friedrichshafen, Germany-headquartered manufacturer of diesel and other engines for off-road and stationary applications, such as mining equipment, tanks and standby power sources.

A machinist cleans a freshly machined part for a diesel engine at MTU America. All images courtesy of Alan Richter.

Because North America is one of MTU’s largest markets, Diebel said, the company wanted to have a manufacturing presence on the continent and brought production of “high-running” parts to the U.S. He considers a part to be high running if it requires at least 100 machine hours per year.

MTU America initially made only the same parts for the same engine models that MTU Friedrichshafen GmbH did. About 2 years ago, however, the South Carolina plant began producing some parts that were not made in Germany, Diebel said. From product concept to delivery consumes about 10 months, but one project had a 4-month timeframe—”and we did it.”

Highs and Lows

The low-volume, high-complexity parts that MTU machines are primarily made of cast iron. Most castings come from Europe. The low volume creates a challenge when a manufacturing change is required, Diebel pointed out. In a high-volume application, the response to a change is almost immediate—parts are produced in rapid-fire succession and a manufacturer can quickly determine whether a part is good or bad after a change occurs.

In contrast, the cycle time for, say, a power takeoff unit at MTU is 3 hours, followed by up to 3 hours more for the part to be washed and then inspected on a coordinate measuring machine. That means up to 6 hours pass before the change is determined to be successful or not.

“As lean as we are, with one-piece flow in sequential production, there are some parts where, if we make a small change, we may be on a totally different part number by the time we get a response from the CMM lab,” Diebel said. “That adds complexity because now the fixture is off the machine or the tooling was changed. We have variables that weren’t there before.”

Assembled diesel engines wait for the next step in their journey.

Diebel said the alternative, which occurs when a change is critical enough, is to run one part, stop production and wait for the CMM results. But with the company’s focus on achieving just-in-time deliveries, MTU tries to avoid taking that route as much as possible.

Cutting tool changes are sometimes made to achieve the company’s annual goal of reducing standard machining times by 3.5 percent, Diebel said. “Last year, a very large percentage of that 3.5 percent was from one change, going from a gundrill to a carbide-tipped drill,” he said, adding that the switch reduced a 14-minute cycle by about 2 minutes.

In another switch, he noted MTU cut multiple minutes out of a cycle time with a new milling cutter. “That thing screams,” Diebel said. “We are always looking for new technologies.”

When considering a new cutting tool, MTU first discusses a specific part feature it is targeting with a manufacturer or OEM, explained Darrell Miller, manufacturing engineer at MTU. The sales and application engineer then recommends a tool that best matches the application, based on its geometry and recommended machining parameters. Next, MTU schedules a date to test the tool by cutting the targeted part feature in one of its machining centers and checking the part with a CMM.

“If successful, we will run the tool till it wears out, which is determined when part dimensions cannot be held,” Miller said, adding that the life of the new tool is compared to the previous one.

Nonetheless, Diebel emphasized that those technologies must create capacity on MTU’s machine tools by significantly reducing cutting times rather than, say, cutting a 30-second tool-change time in half. “That’s not something we need. We have 30 seconds for a scheduled tool change outside the machine.”

Diebel added that the company’s cutting tool cost is about 1 percent of a part’s total cost, compared to an industry average of around 3 percent.

Built on Lean

A cultural transformation built on lean manufacturing principles has led to new growth opportunities at MTU America’s South Carolina plant, enabling workers to provide customers with the highest-quality product, on time and at the lowest cost, the company reports.

Diebel pointed out that producing the highest-quality product requires implementing a production system—the MTU Production System—that includes its guiding principle of having zero defects. This principle is essential because many of the engines MTU manufactures are in mission-critical applications, such as providing backup power for hospitals and rescue ships. “If somebody is in the operating room and the power were to go out, the engine needs to go to rated power within a few seconds and start feeding into the grid,” he said. “There is no acceptable failure rate when it comes to peoples’ lives.”