GM Tonawanda Engine Plant Automation Defies Conventions

TONAWANDA, NY – Despite the promise of greater throughput and better quality with a new automated cylinder-head subassembly process, General Motors Powertrain executive Steve Finch was not an easy sell on the technology.

“When I first saw it, I didn’t want it,” the GM Tonawanda engine plant manager says of the system, which consolidates four machines into one unit. “It looked like one of the most complex, sophisticated pieces of machinery I’d ever seen.”

But then Finch got a glimpse of the so-called smart cell at work on his plant floor, part of a $400 million GM investment at Tonawanda to accommodate production of the next-generation small-block V-6 and V-8 engines for the auto maker’s big trucks and sports cars.

Compared with a traditional assembly line, the smart cell cuts fixed and variable costs by 40% and floor space 60%, GM says. By consolidating older machines, it reduces the number of automated components by 75%. The smart cells cost about $1 million apiece installed.

“It’s turned out to be one of our best pieces of operating equipment,” Finch admits.

Robotics supplier Comau builds the unit and it uses Siemens controls. The smart cell presses in valve seals, flips the part over, installs the intake valves, installs the exhaust valves, flips the part back over, installs the valve springs and keys up the valves.

The three smart cells employed by Tonawanda each install 48 parts into the cylinder head in 40 seconds, which does not include the time it takes for the gantry to place the head into the machine and later remove it.

Collectively, GM says, Tonawanda’s smart cells deliver a completed head every 21.7 seconds on average.

Contained behind a glass door, the automated unit performs precisely choreographed movements with lightning-fast precision. The robots automatically can switch their tools on the fly. The flexibility allows GM to change products without interrupting production, which saves money (see related video: GM Smart Cell Head Assembly).

The smart cells easily can be repurposed with simple tooling changes, GM says, making them adaptable for use on other products. But they are only one piece of a suite of new technologies employed at Tonawanda to build the auto maker’s 4.3L V-6 and 5.3L and 6.2L V-8 engines.

The plant, which also makes 2.0L turbo and 2.5L naturally aspirated 4-cyl. engines, leverages advanced coordinate measuring machines (CMM) to help ensure production of higher-quality engine blocks and cylinder heads.

Tonawanda employs 12 Zeiss Accura CMMs, which use computer-controlled probes to measure the dimensions of machined cylinder heads and engine blocks. The probes examine more than 11,000 data points within 2.5 microns. The programmable systems allow for quick, low-cost modifications based on process and product changes, the auto maker says.

Manufacturing engineers at GM Powertrain headquarters in Pontiac, MI, can monitor the machines remotely and implement software changes as needed.

Six new Hommel-Etamic Wavemove CMMs at Tonawanda also use computer-controlled probes, measuring the surface finish of machined heads and blocks looking for quality-killing bugs such as textural roughness and material waviness.

The units measure the surface finish to an accuracy of less than a micron, or a fraction of the width of a human hair. The machine samples one of every 80 parts, because each part takes about one hour to measure, GM says.

The two sets of CMM systems, which cost a combined $7.2 million to install at Tonawanda, help eliminate production errors. Operated in a temperature-controlled environment, the machines are calibrated daily and certified annually to ensure accuracy of measurements.

“We have very tight tolerances to meet on these engines,” Finch says ahead of a tour of the Gen 5 small-block engine production area here. “And instead of tying up a person to work on these blocks, the robot can do it and we can use that person elsewhere.”

Tonawanda now ranks as GM’s most flexible engine plant, as its boring process can tap any number of cylinders with the same machine without stopping. “It is world-class flexibility. We can make any product anywhere along the line,” Finch says.

In addition, the 3.1 million-sq.-ft. (288,000-sq.-m) plant uses one of the industry’s most advanced track-and-trace quality-control measures. The system employs the same radio- frequency identification used for years by GM and its competitors for tracking the assembly process, but the auto maker says its Gen 5 small-block program is among the first to use RFID-enabled track-and-trace data bolts.

GM says a combined 40 processes are performed on the Gen 5 blocks and cylinder heads, and a data bolt is mounted on each at the beginning of the processes to ensure none are missed.

The data bolts also record the exact time a block or head goes through each machining task. If a problem is discovered, operators quickly can backtrack to locate the error and whether it was an anomaly or part of larger issue.

At the end of the assembly line, the data bolt is removed and reused. The bolts can store up to 2,048 bytes (2 kb) of information. GM admits the storage levels are small by computer standards, but the information can prove invaluable beyond the plant level.

For example, because all the information is stored by the auto maker, if a fault were discovered in a sold vehicle the auto maker could determine exactly how many units must be brought back for repair.

This dramatically narrows what the auto maker calls the “suspect window,” or the number of vehicles GM must assume contain a faulty block or head. It can mean the difference between fixing a handful of vehicles at a dealership or conducting a large and costly recall.

“Collecting data at this level has never been done before – every engine, every part, every day,” Finch says. “It’s saved our bacon already.”

The facility also uses a unique method for leak-testing the high-pressure fuel-injection systems of the new small-block engines. Direct fuel injection plays a key role in the improved efficiency of the engines over their previous-generation port-injection systems.

However, direct injection requires greater scrutiny of leaks at joints along the fuel system, because pressure can reach upwards of (150 bar). Near the end of the build process, GM fills the injector lines with helium and raises the pressure with pneumatically sealed tools that have small collection chambers.

Mass-spectrometer technology measures leak rates at the molecular level, or flows of less than 1 part per billion, according to GM. The system tests for defects less than 100 times smaller than the width of an average human hair.

GM uses helium for the test because it is non-toxic and among the lightest elements, allowing it to pass through leaks heavier gasoline cannot.

Tonawanda’s cutting-edge automation has not displaced any employees. In fact, the level of automation at the plant has decreased and the degree of hands-on manufacturing has increased, as GM seeks to emphasize the craftsmanship of its engine building, says Jordan Lee, chief engineer-Gen 5 small-block engines.

“We think it makes a better engine overall and the employees enjoy it more,” he says.

Tonawanda began production of the engines earlier this year to supply the auto maker’s important redesigned large pickups and the seventh-generation Chevrolet Corvette Stingray. The engines will appear in nine GM products by the end of 2015, and output at Tonawanda will reach about 1,500 units daily once the facility reaches full speed.

Combined with Gen 5 small-block engine production in St. Catherines, ON, Canada, and Ramos Arizpe, Mexico, North American output of the engines will reach 5,000 daily, although Tonawanda will be the only plant producing all three variants.

The factory’s flexibility represents the “newest, latest and greatest” elements of GM’s global manufacturing process, Lee says.

Finch, in his seven years as plant manager at Tonawanda, has seen employment shrink by thousands to just 600 workers during the low point of the recession in 2009 and bounce back to 2,000 on three shifts five days a week.

Last year, Tonawanda built 272,081 engines, including the new GM large 4-cyl. engines and a handful of V-6 models, which have been discontinued. In the coming months, Tonawanda’s customer list will grow to six GM vehicle assembly plants.

“We’re in a turnaround phase, but we’ll get back to 1 million (units) in couple years,” Finch predicts.

The 75-year-old facility has manufactured 71 million engines since production began at the site, which straddles the cities of Buffalo and Tonawanda.

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