Ford Tools Up for Flexible Assembly Capability

Not only has Ford developed the flexibility to assemble different body styles and models on the same line, but even to build vehicles that have entirely different powertrains on the same line. Here’s a look at what’s behind the transformation.

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James Tetreault, Ford vice president, North America Manufacturing, is part of an undertaking that represents a massive change within the Ford manufacturing footprint, one that is providing the vehicle manufacturer with the kind of assembly flexibility that would have been admired by the highly practical and pragmatic Henry Ford, despite his legendary focus on efficiency at the cost of flexibility (“…any color so long as it’s black”).

Flexibility—thanks to technological innovation—is now practical. And what’s more pragmatic than using your assembly line to build what customers want?

Historically, automotive assembly plants have had limited flexibility, especially in the body shop, as a consequence of using fixed tooling to locate, clamp, and—although this is essentially no longer the case—weld vehicles. What’s more, there had been a tendency for locating holes on the sheet metal to be positioned in varying places between models, which mean that it was difficult, at best, for different cars to be run down the same line, particularly in the era of hard tooling.

So at Ford they are making changes in order to handle variety along the line, and Tetreault points out that this isn’t simply a matter of the manufacturing engineers getting more clever at what they do: speaking of the ability to assembly B/C or C/D cars on the same line, he says, “We’ve got to get the locators—the master control holes—for the sheet metal within a certain envelope in order to design flexible tooling. We’ve been working hand-in-hand with our engineering and product engineering teams to do that.”

Flexibility is a team undertaking.

And members of that team can include suppliers, as well. Tetreault says, “We’ve had to invent a number of new assembly processes for sheet metal, the most important of which is called a ‘PLU,’ a programmable locating unit, which we co-invented with a supplier, Fanuc Robotics” (fanucrobotics.com).

Tetreault walks through the main elements in a body shop process:
1. Locating the sheet metal components with the master control holes in the precise orientation for clamping.
2. Clamping.
3. Welding.

“Welding has been flexible for a long time—we’ve had weld guns on the ends of robots for 35 to 40 years,” he says. If there is a difference in that regard, it is that they’re using more robots than ever before, with “very, very few fixed welding guns.” Why? “The reason is simple: with a mix of models in one plant, we want to be able to switch programs and not have tooling specifically designed for one model.”

But this leaves points 1 and 2, the locating and clamping. In addition to having the locating holes being positioned in consistent areas, there is the additional need to be able to find those holes. He recalls visiting Mazda in Hiroshima and seeing what he describes as “the first high-speed or high-volume version of flexible locating.” This system was based on small robots that had pins on their end effectors to mate with the master locating holes. This provided the means by which there could be variation in vehicle size, as the robots could move as needed. “We looked at that and figured that if we got to flexible clamping, we’d get to a fully flexible body shop; we wouldn’t need to hard-tool anything. That’s what we’ve been working on: clamping sheet metal. That’s a little more difficult than it sounds. You’ve got complex surfaces on sheet metal on parts you want to clamp. There is a lot more variability on surfaces that need to be clamped from model to model than a master control hole for locating sheet metal,” he says. Lining up holes is one thing. Holding together sheet metal with fluidic forms is quite another.

So that led to the development of the PLUs, which allows locating and clamping. The initial application was at the Ford Cuautitlán Stamping and Assembly Plant in Mexico, where the Ford Fiesta is produced. The second application is at the Michigan Assembly Plant (MAP), on the body side lines. And there will be a more extensive application at the Louisville Assembly Plant, which is expected to become Ford’s most-flexible high-volume plant in the world when it restarts production in late 2011.

At present, however, MAP is Ford’s flex facility. The company spent $550-million on retooling the facility (where they used to build products including the Ford Expedition and Lincoln Navigator, not C-segment cars), which will be the first in the world to build gas-powered, electric, hybrid, and plug-in hybrid vehicles on the same line. They’re currently building the gasoline-powered Ford Focus at the plant; the Focus Electric is slated to come on line in late 2011, and the C-MAX Hybrid and the C-MAX Energi plug-in hybrid—five-passenger multi-activity vehicles—are scheduled for production in 2012.

Tetreault acknowledges that when it comes to powertrain variants like these, “most of our competitors build them on dedicated lines in their plants.” So why all on one line at MAP? “Our goal was to be flexible on the main assembly line so that we can accommodate a shift in demand.”

That is, say they’re running 70 jobs per hour on the main line. If they had a dedicated line for hybrids, it is likely that it would be short, having a capacity on the order of 10 jobs per hour. But what if demand jumps such that they need 20 jobs per hour? He says that by doing the assembly on the main line, it is simply a matter of changing the build schedule to accommodate the increased demand for hybrids in this scenario.

What’s more, the flexible assembly provides the means by which they can add a new model—say the next-generation Focus—or even something “quite different than what we’re building there now” without shutting down and retooling the plant.