Fly high on a thread

Only several of more than 2,600 F-35 Lightning II aircraft that Lockheed Martin eventually will build have rolled off the end of its assembly line in Fort Worth, Texas, but Charles T. “Tom” Burbage already sees signs that the production strategy for this plane—also known as the Joint Strike Fighter (JSF)—is working. Burbage, an executive VP with Lockheed Martin Aeronautics and general manager for F-35 JSF Program Integration, says one key milestone was smooth mating of the major subassemblies.

To cut F-35 production cycle time versus previous-generation aircraft, Lockheed Martin Aeronautics and its partners are simultaneously producing major sections of the aircraft at different feeder plants, and joining or “mating” the assemblies at the plant in Fort Worth. This is a departure from strategies on past aircraft like the F-16, says Burbage, where, “Basically, we bring raw materials in one end of the factory, and roll an F-16 out the other end.”

But on a plane as complex as the F-35—which features much more use of composite materials and greater emphasis on stealth than earlier-generation fighters—the feeder plant strategy required a high degree of control over tolerances. To compensate for potential problems when the first aircraft were assembled, says Burbage, the initial design allowed for some precise shimming to enable a perfect fit between the structures.

“We found out that the major subassemblies came in with exactly the gaps we had programmed,” Burbage says. “So we've now taken the gaps out, and essentially, we are doing the final-mate process with no mismatches.”

This smooth mating, says Burbage, indicates that the company's “digital thread” for managing F-35 information is working. The digital thread concept, says Burbage, starts with 3D solid models that design engineers create using the CATIA CAD package from Dassault Systèmes, and extends into other areas of product life-cycle management (PLM), including production management, where the company has rolled out manufacturing execution system (MES) software from Visiprise to handle functions such as electronic work instructions and control over production status and serialized parts data. The company uses the TeamCenter system from Siemens PLM Software to manage the product record and enable collaboration around designs. Other applications, including an ERP system from SAP that the company is phasing in, also can tap into this digital thread.

The end result, says Burbage, is all the functional areas have what amounts to a virtual database for product-related information.

“The digital thread goes from conceptual design to detail design, and on into manufacturing,” Burbage says. “It extends into our [equipment] training systems, and our maintenance system. That same digital thread that starts with the design engineers is used for the entire life cycle of the airplane.”

On plant floors, the thread allows for lightweight 3D images to be embedded within the electronic work instructions. This tends to improve the productivity of the shop-floor mechanics versus use of 2D blueprint screen captures used on previous-generation planes.

“We use three-dimensional, graphically enhanced images that the mechanic on the floor can refer to, enlarge, look at in detail, or rotate,” says Burbage. “Basically, it captures the power of visualization.”

The digital thread supports the company's strategic move toward a more network-centric approach to production. Burbage says the F-35 manufacturing strategy is based on building large, fully validated subassemblies and bringing those together in a rapid mate and assembly process. “This methodology allows us to build major sections of the plane in parallel, thereby substantially shortening the cycle time required to manufacture this very complex and sophisticated end item,” says Burbage.

Besides the smooth mating, other signs also point to the thread's effectiveness. One recent milestone: On Dec. 18, 2007, the company rolled out the first Short Take-Off & Vertical Landing (STOVL) variant of the F-35, hitting the date it had scheduled 15 months earlier. In addition, all of the projected milestones for mating and assembly occurred on or ahead of schedule with the STOVL, and all four center fuselage deliveries from partner Northrop Grumman hit their target dates.

What's more, says Burbage, the major assemblies are arriving at Fort Worth with little or no “traveled work,” which means that mechanics at Fort Worth don't have to go back to complete work left unfinished at a feeder plant.

“We are seeing much better than legacy results in terms of quality and fit up, and we expected to see that, because that should be the payoff of the digital thread,” says Burbage.

Other factors aiding the manufacturing strategy include greater use of automated drilling. The company also tapped into the knowledge of plant-floor workers, which led to suggestions such as building the F-35's wing assembly in a large vertical work stand that affords ergonomic standing positions.

Burbage says the more network-centric approach has its challenges, including a learning curve among suppliers when it comes to getting the proper machines in place to cut parts for the F-35. Another challenge is coordinating procurement and scheduling across the supply base. Today the company uses a custom system it calls its Production & Inventory Optimization System, or PIOS, for manufacturing resources planning, though it began using ERP software from SAP in January 2008 for financials.

Eventually, SAP's software also will be used to handle supply chain management, but for now, PIOS is used to plan activity for the supply base. The coordination of plants around the end schedule, says Burbage, is another aspect addressed by the master data in the digital thread.

“One of the things the digital thread does is ensure that those processes not readily visible on the factory floor are in fact synchronized with the same kind of pull that the factory floor requires,” Burbage says.

“In the late 1990s, when the F-35 program was coming together, there was a huge emphasis on cost efficiencies as part of the program, and participants realized there had to be a paradigm shift in the way that fighters, in general, were built,” says Cook. “The industry—including Lockheed Martin—knew it had to seek out new production modules, and borrow techniques from other sectors, including automotive.”

Lockheed Martin Aeronautics began its MES initiative in 2002, starting with Visiprise software for process planning and change management, followed by functions for shop-floor management. Currently, Visiprise is running at four of the company's plants. Besides the Fort Worth location, these include sites in Clarksburg, W.V.; Meridian, Miss.; and Marietta, Ga.

The functions used include electronic work instructions, workflow and process modeling, order status, engineering change support, and quality records tracking, such as ensuring that all nonconformance records are closed, and required data fields are populated. The work instructions embed a lightweight, dynamic 3D image that is consistent with the 3D model created in CATIA, and with lightweight “JT” files used for collaborative design.

According to Brad Leech, senior manager of manufacturing engineering, the MES saves time and lends greater accuracy to shop-floor processes versus the 2D blueprints and manual collection of specifications common to earlier projects. “We've tried to create a one-stop shop where the mechanics have everything they need to support the aggressive cycle times that are needed for the F-35,” says Leech. “In terms of quality steps, the MES also enforces better control of shop-floor processes. It doesn't allow for short cuts.”

The hand off between design and manufacturing begins during design, when the manufacturing engineers and process planners begin working with design engineers to author 3D work instructions, says Leech. The Visiprise Manufacturing module handles many of the classic execution tasks, and is interfaced with a time & attendance system to closely track labor.

Leech sees the role of the MES as one of controlling product definition data through each manufacturing step, as well as guiding work and quality control processes.

“The MES provides real-time access to configuration control data,” explains Leech. “It provides consistent processes and tools across all sites and mechanics.”

Lockheed Martin Aeronautics began its MES initiative in 2002, starting with Visiprise software for process planning and change management.

With past aircraft programs that relied heavily on paper, processes could easily go astray. For example, Burbage says, if a quality assurance inspector found a misaligned part, he would write up the problem on a carbon-copy form, and send one copy to engineering so that the misalignment could be corrected. Trouble was, it was easy to transpose part numbers when filling out the form, and the form, once manually delivered to engineering, might sit in an in-box for days. “Now, it's very accurate because you basically pull up a 3D image, click on the part in question, hit 'send,' and it goes to the engineer with all the details accurately filled out,” Burbage says. “And it shows up on the engineer's laptop instantly. It doesn't go sit in a queue somewhere.”

Burbage sums up the streamlined production management process with MES as just this: “It's simple; it's very accurate; and it goes at the speed of light.”