Engines are complicated, and a lot can potentially go wrong during assembly—malfunctioning machines, faulty parts, and, of course, human error. But at its factory in Tonawanda, N.Y., General Motors has taken a high-tech approach to preventing and catching these problems. And it's all thanks to a humble little bolt.
The 75-year-old factory recently underwent a $400 million upgrade to start building a new line of Gen 5 six- and eight-cylinder engines. It's the first of the automaker's manufacturing facilities to implement a new "track-and-trace" system by using radio-frequency-identification (RFID) technology. GM has used RFID tags in its factories for more than 10 years to identify assembled engines, but now the company is attaching them directly to the cylinder heads and engine blocks using what the company calls a data bolt. It's shaped like a regular bolt and is threaded on one end, but the head is hollow. Inside, secured with epoxy, are a memory chip (or RFID tag) and a coiled metal filament, which acts like an antenna.
As its name implies, the data bolt stores information—2 kilobytes' worth, to be exact. That's a very small amount of data by modern standards (only a fraction of an MP3 audio file's 3 to 5 megabytes). But it's enough to record every single manufacturing process the engine block or cylinder head undergoes. And that is the key to the whole track-and-trace system: All of the data from each bolt gets uploaded to servers housed at the factory.
Down the Line
In total there are about 50 different points throughout the production line where data gets transferred to and from the bolts. Just about every automated machine on the line has an RFID scanner to read the data bolt before it performs its task, and another RFID writer that logs new information onto the bolt once the machine has done its job. If any of the machines on the floor do not complete their duties to perfection, the next machine in line can tell and will shunt any out-of-spec engine block or cylinder head off the line to be inspected by a worker.
When the cylinder heads and engine blocks are joined at General Motors' engine plant in Tonawanda, N.Y., the engines are mounted onto pallets that have their own RFID tags with which the cylinder head and engine block serial numbers are merged. By then, the assembly information recorded by the RFID tag in the data bolts has already been backed up to a central server for easy retrieval. Photo by Jeffrey Westbrook.
Likewise, if a block or head gets pulled to undergo a gauge test for appropriate tolerances but somehow gets left offline at the end of a shift, it can't be put back into the wrong place in the production process, which sometimes used to happen. "That has saved us a couple of times already," Peter Laskiewicz, a manufacturing process engineer for GM, says, "especially during launch, when you've got a lot of parts everywhere and are trying to understand where they go." Skipping a single process could crash one of the 30 new digitally operated milling machines that use computerized coordinates to hone surfaces and drill and top holes in the engine blocks and cylinder heads. Such mistakes can cost the company about $1 million apiece, Laskiewicz says.
Once the cylinder heads are fully milled, they're attached to the block using a machine that screws down all 20 bolts at the same time. Here again, the RFID tracking is invaluable, allowing workers to tell whether each bolt was successfully installed. This is also critical, because some bolts require such a precise tolerance that they can only be torqued and retorqued a certain number of times. In the past if a bolt attaching a bearing cap to an engine block got flagged for improper tolerance, for example, a worker could retry and sometimes get it to pass muster, even if it wasn't fully within spec. And that was an oil leak just waiting to happen.
Although quality control during the manufacturing process is the main goal of the new data-bolt RFID system, it is also proving to be a huge help in post-production troubleshooting. If a supplier notifies the factory of a bad batch of parts, it's easy to zero in on the exact engines on which they were installed using the database of information saved from the bolts. General Motors plans to implement the track-and-trace RFID system in other factories but hasn't said when it will do so. Marc Brazeau is a director with AlixPartners, a global consulting firm with expertise in manufacturing processes. Brazeau says that what GM is doing is exciting and has the potential to spread to industries such as appliance manufacturing: "Four or five years from now you're going to see a lot of different types of applications."