When completed, the Joint Strike Fighter will be the world’s most advanced stealth fighter and as it goes through the development phase, engineers are using 3-D design software and laser tracker technology to ensure that this national security asset and engineering icon will be rivaled by no other aircraft.
Lockheed Martin (Fort Worth, TX) has led the effort to bring the Joint Strike Fighter (JSF) to fruition. Partnering with Northrop Grumman and BAE Systems, Lockheed has formed the JSF Team—a group of industry experts pouring ingenuity to areas critical to the program’s success. These specialists focus on one principal concept: a common design with affordable, lethal, survivable, and supportable variants that fulfills the distinct needs of each military service.
The resounding mandate of the JSF project is leaner-than-lean manufacturing based upon a technical recipe called “the digital thread.” The JSF program embraces elite concept-to-asset practices without reinventing the wheel.
The digital thread
The digital thread starts in the JSF design phase and distributes its benefits throughout every process. According to JSF spokesperson John Kent, the fighter will be the first aircraft entirely designed in 3D solids using CATIA software. Three-dimensional solid models provide an exact representation of each part, thus forming the foundation of the digital thread. JSF will take full advantage of the digital model and carry this product data, this thread, into simulation, tooling, fabrication, assembly and mating.
Everyone involved in the project, at varying degrees, will use the same precision product data including the assembly line, the supplier, the CAM programmer and the laser tracker operator. Moreover, this methodology diminishes the paper chase characteristic of traditional engineering, and saves the customer millions of dollars by eliminating the need for expensive upfront tools. Additional savings will be realized in the long run because maintenance costs are also reduced.
Setting the stage
“Back in 1997, when we started the process of building the JSF concept demonstrators, there were two things done in parallel,” says G.B Bailey, director of JSF Manufacturing Integration. “From the onset, we knew we had to build three variants, and we knew we could not put all of the advanced manufacturing technologies into the CDA concept. But there were a number of key manufacturing processes we eventually wanted to use on the airplane. So while designing and building the three variations of the aircraft conventionally, the JSF team began to survey the processes we wanted to use on the production JSF. We initiated an Airframe Affordability Demonstration program that would allow these technologies to ‘win’ their way on to the program.”
The Airframe Affordability (AAD) program is exhibited in a high visibility demonstration area located on Lockheed’s one-mile-long shop floor. The area consists of JSF tooling and components that are used to illustrate manufacturing processes in both the detail and the assembly level.
“Between Lockheed and our JSF partners, we were able to scrutinize the manufacturing methodologies of almost every modern war fighter — F-16, F-22, F-117, B-2, Eurofighter, F-18 E/F. All processes implemented have demonstrated they are low risk and a real asset to the production of the aircraft. So in the AAD area, this is the best-of-the-best competition. We will use these enablers to pull the digital thread through the entire JSF program,” says Bailey.
Laser tracker
At the AAD location, Lockheed uses an industrial laser tracker during its main demonstrations to show module-mating concepts. The state-of-the-art laser tracker is a precision instrument used in conjunction with an engineered jacking system to execute a JSF final aircraft mate demonstration. The laser tracking technology is used to set up, measure and inspect assembly-tooling details based on CAD models. The 3-D laser interferometer and angular encoders deliver a high-speed measuring rate of 1,000 points per second, and a measurement volume of 70m diameter.
Rina Molari, in-house measurement/inspection expert and member of the manufacturing engineering staff, is responsible for gathering and analyzing the data collected by the laser tracker. During the AAD demonstration, Molari performs the module mate alignment manually by driving the tracker’s laser beam and target ball out to each of their six check points, which are small circular slots designed into the tool for this application. After a reading, she will adjust the jack system and watch the laser tracker feedback coordinates until the mate is aligned. The next step is simple, the aft fuselage slides into position for connectivity.
“Each day before I start a job or an AAD demonstration using the laser tracker, I perform a quick system check and when the indicator comes back, it confirms the system is working well,” says Molari.
Final aircraft mating
Although the laser alignment mate system concept is new to the Fort Worth facility, other industry partners have this type of equipment and reported very good results. Chet Burge, JSF Airframe Mate and Delivery Integrated Product Team Lead, cites the technology has proven itself and the team has adopted this type of system for JSF.
“When people first see our mate joint concept on the AAD floor, there are a lot of questions. But this is not a new concept,” states Burge. “BAE SYSTEMS used this joint concept for the Tornado fuselage mate, and it is also similar to the F-16 wing attach joint. This mate joint has machined planes with pre-drilled holes on each module, which allow them to simply be aligned and bolted together. To do this mate concept on the earlier programs, control tools and gages were used to maintain close tolerances. Those control tools were shipped all around the world to wherever the aircraft were built. “On the JSF, we are mating four complete modules that plug and play. We eliminate the control tools and gages through the use of coordinate data derived from the digital thread, and by having processes and machines to accomplish this level of tolerances. The laser tracking allows us to validate our designs and close tolerance work on the JSF. In the past, we did not have the real-time measurement capability to confirm tolerances. Today, we can do inspection work on the fly and the resultant data is a by-product of doing the task. 3-D CAD, the Internet, going directly to NC, and the laser tracking systems all create a strategic loop for precision in the JSF program,” says Burge.
According to Burge, theoretically one person could do the whole mating process, but for safety reasons more people will be involved. When compared to the F-16 and other aircraft mating systems, the JSF mating process is faster. Today it takes about 8-10 days, depending on what flavor of F-16, to mate the aft fuselage with the center fuselage. Going back to the digital thread, what makes JSF unique is its simple mate joint design. Merge that efficiency with the laser tracker and the jack system, and the result is a rapid, accurate procedure. Burge projects the JSF mate will be completed in about a two-shift operation. So instead of ten days, its mating cycle will be more like 20 hours.
When the production schedule is set up, even on Ship One, Lockheed will have five working days to load components into the tool, align them, bolt them together, and install the main landing gear. After the company completes 200 to 300 JSFs, they estimate those same tasks can be accomplished in one TAKT day of about 19 hours.
“When producing 17 airplanes a month, which is capacity, and delivering one JSF every two shifts, you do not want anyone doing best-fit, trial-and-error, or trying to do alignment without a measuring device,” says Burge. “We will see cost savings from reduced labor, and, if you look deeper, the possibility of even eliminating rate tools. We forecast that there will be only two tools needed to mate the aircraft when we are running at capacity. When compared to the F-16, when they were running at full rate, which is 20 to 22 airplanes per month, that program had about nine tools at the mate stations.
The measuring system allows Burge to line up the fuselage, and it rolls and bolts together to the rest of the plane. In addition to mating the aft fuselage, all of the JSF joints are designed using this concept and joined in a similar manner— the wings to the center fuselage, and the forward to the center fuselage. All four components will be mated using this technique to drive the process.
The JSF mate process will enjoy further timesavings after the operation is automated. Eventually, the laser tracker can be pre-programmed for point-and-shoot measuring and will search out the coordinates.
The tracker laser beam will be shooting toward each target awaiting the operator to put the target into the check point hole. The operator will be able to move around the area freely, and if a beam is broken, it can be retrieved at its last location. Burge’s team is also looking at how they will further integrate laser tracking into their mating process. Using an APS that attaches to the tracker, they could allow the tracker to literally drive the jack system. This would automate a large portion of the operation, and let the feedback guide the operator. Later this year, tooling suppliers will be brought in to preview several concepts.
Quality built into tooling
The JSF program incorporates another primary laser tracking application. “A lot of our tools are being designed and built with tracking systems in mind,” continues Burge. “The work we have seen to date on the F-22 shows that the part fit capabilities are very good. The tracker is a huge tool in allowing us to pull this thread all the way through the design-build on JSF.”
“One thing you will notice in the AAD demonstration area is modular tooling,” reports G. B. Bailey. “Quite a contrast to the F-16 line that has rigid welded structures that are very difficult to change. With the JSF modular tooling concept and the use of the laser tracker, you can set a locator and put your locating eye directly on it. Tomorrow, if you want to make a change to a detail that locates with a laser tracker…it can be done very easily. With this type of configuration, it allows the program to constantly upgrade our processes without expensive changes to the tooling. And again, we can tailor the airplane to satisfy the efficiencies of the variant of the service, without paying the price in the number of tools.”
When assembling the tools, Lockheed will track a locating point over the life of the tool to see if there are any variations. Using the laser tracker, they setup 3-D coordinate points in space and verify them initially and on an ongoing basis. In fact, one of the criteria for becoming a participating tool manufacturer for the JSF program is the supplier must demonstrate they have the capability to use laser trackers, and those features will be designed into the tool.
“With the tight tolerances we are trying to maintain for this program, you have got to be able to fabricate and validate a tool quickly and accurately, ” said Burge. “When building a conventional aircraft, a lot of time is spent loading and unloading fixtures. For the JSF, we are eliminating this operation. We will build the assembly in a tool, move the tool and assembly down the production line using the same tool throughout the assembly process. This is one idea that helps us achieve a 90% reduction in tools.”
Sidebar:Tech tips
* The Joint Strike Fighter is being developed with one principal concept: a common design with affordable, lethal, survivable and supportable variants.
* In developing the aircraft, the JSF team scrutinized the manufacturing methodologies of almost every modern war fighter — F-16, F-22, F-117, B-2, Eurofighter, F-18 E/F and incorporated the best technologies.
* The laser tracking technology is used to set up, measure and inspect assembly tooling details based on CAD models.
* The 3D laser interferometer and angular encoders deliver a measuring rate of 1,000 points per second, and a measurement volume of 70m diameter.
* The tracker laser beam shoots toward each target awaiting the operator to put the target into the check point hole. The operator can move around the area freely, and if a beam is broken, it can be retrieved at its last location.
Sidebar: Electronic documentation and training
With the digital thread, the JSF team will use electronic work instructions. The intent of the JSF program has been to eliminate 2-D drawings. For the CDA aircraft, more than 200 NC parts were built at Lockheed, with no drawings. It was a 100% digital process.
As shown in the AAD demonstration simulation, the company can generate working steps based on the 3-D models to illustrate how to use the laser tracker. Using a process automation module, Rina Molari, in-house measurement/inspection expert, can program the system to prompt the operator for each step as the laser tracker acquires data. This method will foolproof the system and also remove manual error.
The JSF program also aimed for 70 to 90% of common parts on all three variants, so the learning curve would be shortened for those involved in assembly. In reality, there is about 80% uniformity in all the parts. Once again, the digital thread allows the mechanic, or any party who needs access, to call up 3-D visual assemblies and electronic instructions when needed. Lockheed projects that maintenance cost for the airplane will plummet to about half the cost of the current generation of fighter planes as field personnel have immediate access to an accurate reference information and improved throughput speeds.
