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Aug 15, 2016 | Wheelift

Northrop Grumman Soars With Automation

For decades, automotive engineers have looked to the aerospace industry for new ideas. Back in the 1930s and 1950s, Detroit was inspired by the sleek designs of innovative airplanes such as the Northrop Alpha and the Grumman F4F Wildcat.

But, the tables turned recently when engineers from Northrop Grumman Corp. paid a visit to several automakers and their automation suppliers. They were looking for fresh insight on ways to streamline military airframe production.

The result is a new assembly line in southern California that may change the way future generations of aerospace engineers approach production, just like Ford’s Highland Park plant revolutionized the auto industry a century ago.

Indeed, the Integrated Assembly Line (IAL) represents a significant shift in the way that airframes are assembled. It has enabled Northrop Grumman to achieve a 450 percent increase in throughput.

The IAL is housed in Plant 42, a government-owned facility in Palmdale, CA, operated by Northrop Grumman Aerospace Systems. It’s a world-class operation that provides assembly, integration, testing and long-term maintenance capabilities for some of the world’s most advanced aircraft. The secretive site in the Antelope Valley of the Mojave Desert is strategically located just a few miles south of Edwards Air Force Base.

The two-year-old IAL produces the center fuselage of the F-35 Lightning II, which will become the backbone of the U.S. military for the next three decades. Once production fully ramps up in a few years, assembly time for the new supersonic stealth aircraft will be less than half that of current-generation fighters. The IAL will play a key role in meeting that target.

“The IAL maximizes robotics and automation, providing additional capacity and assembly capability, while meeting engineering tolerances that are not easily achieved using manual methods,” says Brian Chappel, vice president of the F-35 program at Northrop Grumman. “It is central in producing the F-35’s center fuselage, as well as increasing the program’s affordability, quality and efficiency.

“The IAL design uses a system-engineering approach to integrate tooling and structure transport, system automation, automated drilling cells, and tooling mechanization coordinated across multiple build centers,” explains Chappel.

Northrop Grumman’s Palmdale facility is the recipient of the 2013 Assembly Plant of the Yearaward sponsored by ASSEMBLY Magazine. The innovative plant was chosen for the 10th annual award because of its ground-breaking approach to airframe assembly.

“Having traveled and visited almost every airframe manufacturing plant worldwide, including China, India and Russia, I believe they set the standard for automation and the application of advanced digital manufacturing on a modern airframe assembly line, commercial or military,” says George “Nick” Bullen, an aerospace consultant who recently retired from Northrop Grumman as principal engineer and technical fellow.

“Their design, development and application of automated drill and countersink machines, automated coating application systems, and moving assembly lines have resulted in significant cost reductions, quality improvements and safety enhancements,” adds Bullen.

According to Bullen, no major aerospace company has ever contracted to design and build an entire integrated assembly line. “Typically, large aerospace manufacturers are their own integrators, bidding specific parts of the assembly line from different suppliers and then integrating them,” he explains. “The IAL is a significant step for the industry.”

Proud Heritage

It’s hard to beat Northrop Grumman when it comes to its long history of aerospace engineering excellence. Although the company was founded only19 years ago, it traces its roots back to the early days of aviation, with heritage companies such as Northrop Aircraft Inc., Grumman Corp. and Ryan Aeronautical Co. Those firms were headed by creative engineers who weren’t afraid to push the envelope.

Jack Northrop started out designing super-sleek mail planes in the early 1930s. One of his big breakthroughs was an all-metal monoplane that enhanced performance and extended airframe life.

During World War II, Northrop built aircraft such as the Black Widow interceptor and the X-56, which featured the first all-magnesium, all-welded airframe in the world. The company developed a new process called Heliarc welding to assemble the aircraft (the process is now known as tungsten arc welding).

In the late 1940s, Northrop turned its attention to developing experimental aircraft, such as flying wings. In fact, its YB-49 predated the B-2 Spirit stealth bomber by more than 50 years.

Grumman Corp. was founded on Long Island, NY, in 1930 by Leroy Grumman. The company has been synonymous with naval aviation ever since. During World War II, Grumman developed an advanced fighter that featured the first practical folding wing mechanism, which allowed aircraft carriers to store more planes.

Another famous Grumman creation, the F6F Hellcat, featured a simple, straightforward design that became legendary during many battles in the South Pacific. The robust and maneuverable fighter was easy to mass produce and maintain.

During the late 1960s, Grumman engineers designed and assembled the Apollo lunar module for NASA. The company was selected for the risky mission because of its long experience building products that could withstand rough landings.

T. Claude Ryan founded the firm bearing his name in the mid-1920s. It’s the company that designed and built Charles Lindbergh’s famous “Spirit of St. Louis.” During the 1950s, Ryan created aircraft for short-takeoff-and-landing and vertical-takeoff-and- landing applications, in addition to target drones such as the Firebee.

In the late 1950s, Ryan engineers pioneered an explosive metal forming technique that allowed the company to manufacture many uniquely shaped aerospace components, such as rocket nose cones and curved domes for missiles.

The spirit of Northrop, Grumman and Ryan are still alive today at the 2013 Assembly Plant of the Year. In fact, their photos greet visitors in the main lobby of the Palmdale complex.

Northrop Grumman also has a tradition of forward thinking on the plant floor. For instance, in 1953, Northrop engineers built the first continuous rail pulse mechanized assembly line for a military airframe. The overhead rail assembly and installation line enabled assemblers to easily switch between the F-5A, F-5B and T-38 jet fighters.

A pair of elevated rails held center fuselages off the floor, which allowed easy access for assemblers. That eliminated ergonomic issues and concerns, while also improving error proofing. Each rail-suspended fuselage was manually moved from station to station by two assemblers.

In the late 1980s, Northrop engineers studied the effectiveness of automation by using robots to fabricate and assemble the wingtips of the T-38. In 1997, they pioneered the first automated drilling machine used on an aircraft assembly line.

And, 10 years ago, Northrop Grumman implemented a sequential universal rail fixture at the Palmdale plant to move parts and subassemblies between workstations. The material handling system reduced the use of traditional overhead cranes and large assembly jigs.

The Northrop Grumman engineers behind the IAL are also used to producing innovative aircraft. In fact, the automated assembly line sits on the same site where the B-2 Spirit stealth bomber was secretly built two decades ago.

Today, the IAL shares the Palmdale plant with production lines that turn out unmanned aircraft such as the MQ-8C Fire Scout, the RQ-4 Global Hawk and the MQ-4C Triton, in addition to various experimental and classified projects, such as the RQ-180 and the X-47B.

Futuristic Fighter

The F-35 Lightning II is a stealthy, supersonic, multirole, next-generation fighter designed to meet the requirements of the United States and its allies well into the 21st century. It will be four times more effective than legacy aircraft while performing a wide variety of ground attack, reconnaissance and air defense missions. According to some experts, the F-35 will probably be the last manned fighter built for the U.S. military.

The single-engine aircraft is the creation of the Joint Strike Fighter (JSF) program, which calls for three variations of the same basic aircraft—sharing a common design for more than 20 percent of the airframe—to serve multiple branches of the military. The controversial $400 billion program has been under development for more than a decade.

Pentagon officials believe the one-size-fits-all approach is an effective way to replace their aging fighter fleets, which have an average age of 23 years. The fifth-generation JSF stealth fighter is designed to replace a wide range of existing aircraft, such as A-10s, F-16s and F/A-18 Hornets.

In addition to the United States, eight partner nations also plan to deploy F-35 aircraft: Australia, Canada, Denmark, Holland, Italy, Norway, Turkey and the United Kingdom.

Lockheed Martin Corp. is the prime F-35 contractor, while Northrop Grumman and BAE Systems Inc. are principal partners. BAE assembles the aft fuselage and tail at its plant in Samlesbury, England, while Northrop Grumman builds the center fuselage in Palmdale. All subassemblies are shipping to Lockheed Martin’s factory in Fort Worth, TX, for final assembly.

Assemblers in Palmdale build three variations of the F-35 center fuselage. While they share many similar wiring harnesses and pneumatic lines, each variant has unique parameters and requirements that make assembly challenging.

The U.S. Air Force uses a conventional takeoff and landing variant that features an in-flight refueling door at the top of the center fuselage and an internal 25-millimeter, four-barrel Gattling gun.

The U.S. Marines use a version of the F-35 that’s capable of short-takeoffs-and-vertical-landings. It features a lift fan and air ducts at the top and sides of the center fuselage and two vents underneath.

The U.S. Navy has a carrier variant that features an aluminum structure in the aircraft’s center fuselage to help absorb stresses during a catapult takeoff. This aircraft also sports a tail hook and larger wings that enable short takeoffs from aircraft carriers.

The Marine variant of the plane, the F-35B, is currently being tested and is expected to begin military operations in 2015. The Air Force variant, the F-35A, will enter operation in 2016. The Navy variant, the F-35C, is due to being operations in 2019.

The production run for the F-35 calls for more than 2,000 copies. That’s considered high-volume in the aerospace industry and makes investing in auto industry-inspired automation cost-effective.

Complex Assembly

However, building jet fighters is much more complex than mass-producing sedans or pickup trucks. Airframes are challenging to assemble because of incredible tolerances, confined spaces and stringent quality requirements. Many types and sizes of fasteners are used, and even the smallest surface discontinuity can affect the stealth performance of an aircraft.

“A modern military airframe is the most complex manufactured assembly in the world today,” claims Bullen, who founded the Aerospace Automation Consortium in 2003 to address industry needs and create dialogue on common manufacturing challenges. “Compounding its manufacturing complexity are exacting tolerances and demanding processes that complicate the application of robotics and automation.

In addition to undergoing severe variations in altitude and air pressure while in flight, military airframes must withstand all sorts of radical twists, turns, strains, stresses and other forces.

Airframes also are exposed to radical temperature extremes. After sitting on a tarmac where skins can expand and contract in surface temperatures that often reach more than 100 F, supersonic jet fighters climb quickly to cruising altitudes where the air temperature is -40 F or colder.

To perform under those demanding conditions, military aircraft require thousands of holes that must be precisely drilled, countersunk, and filled with rivets, screws and other mechanical fasteners. The process becomes even more complex, because military airframes are assembled from a variety of dissimilar materials, such as aluminum, titanium and carbon-fiber composites, in varying sheet thicknesses.

Aerospace drilling and fastening applications require tight tolerances to produce high-strength airframes that can avoid the risk of cracking. Because one bad hole can cause catastrophic failure, everything from hole diameter to critical edge distance to straightness of the hole is critical.

On the F-35 center fuselage, hole diameters range from 0.19 to 0.25 inch. According to Bullen, the centerline placement of the hole in relationship to the substructure cannot vary by more than +/- 0.010 inch with a diameter tolerance of 0.0015 inch.

Not surprisingly, drilling accounts for 85 percent of the quality issues and 80 percent of lost time due to injuries in airframe assembly.

Northrop Grumman led the way when it came to applying automation to solve this challenge. “Early on, it recognized that 65 percent of the cost of an airplane was resident in the airframe and 65 percent of that cost was in assembly,” says Bullen. “The cost reductions that were derived from the first automation of an airframe were directed toward drilling and countersinking; that represented the greatest cost driver for airframe assembly at 60 percent.”

In 1997, Northrop Grumman engineers developed the aerospace industry’s first automated drilling and countersinking machine. When applied to the F-18 E/F vertical stabilizer, it resulted in a 33 percent cost reduction over previous manual methods.

“This led to other applications and to the first automated drill-countersink machines at Airbus, Boeing and Lockheed Martin,” says Bullen. “These machines still represent the heart of the IAL line and provide the greatest direct cost and indirect savings to the assembly of airframes.”

And, the heart of a military airframe is its center fuselage. That’s because everything connects there, including forward and aft fuselages, wings and landing gear. On the F-35, some loads are transferred directly through the skins of the center fuselage vs. internal frames on older-generation fighters.

The center fuselage also contains critical components of the F-35, such as air-inlet ducts, fuel tanks and fuel lines, in addition to electrical, hydraulic and pneumatic systems. A large internal-weapons bay plays a critical role in the F-35’s stealth capability.

The center fuselage of the F-35 houses sophisticated electronics, such as the AN/AAQ-37 distributed aperture system, which is manufactured by Northrop Grumman. The multifunction infrared system provides missile warning and navigation for pilots.

Northrop Grumman also designs and builds the F-35’s radar system and other key avionics, such as electro-optical systems and communications, navigation and identification subsystems, at its plant in Charlottesville, VA. Electrical wiring housings are assembled at a Northrop Grumman plant in New Town, ND, and shipped to Palmdale.

The F-35 is built from around 40 percent composites by weight—more than any other jet fighter in existence. Carbon-fiber skins, such as forward and aft air-inlet ducts and weapons-bay doors, are made in-house at Northrop Grumman’s state-of-the-art facility in El Segundo, CA.

A kanban pull system ensures a constant supply of skins, which arrive at the IAL on an as-needed basis. This process is applied across the supply chain to minimize inventory at the Palmdale plant.

New Production Philosophy

To address reliability, quality and safety concerns, aerospace manufacturers have talked about using robots for many years. However, most efforts have been hindered by accuracy issues and low production volumes.

The industry has continued to rely on large, monument-style assembly jigs and traditional fixed automation, such as large gantry systems and product-specific fixtures. Unfortunately, gantry machines are expensive. And, they typically have limited throughput and require a large footprint.

Unlike gantry systems and other islands of automation, robots are more flexible and can be quickly deployed at a fraction of the cost of custom-designed machines. Other benefits over fixed automation include process repeatability, increased uptime, reduced scrap, reduced maintenance costs and a reduction in jig-fixture requirements.

The IAL represents a huge breakthrough in using robots to develop low-cost, flexible airframes with improved throughput and cycle times. It was inspired by automation systems used by American automakers and was developed with the help of KUKA Systems North America LLC.

Planning for the IAL started more than five years ago. “The JSF program challenged us to achieve significant affordability goals,” says Mike Jones, director of Palmdale manufacturing operations and deputy site manager. “It was an opportunity to eliminate standalone islands of automation and develop an assembly line as an integrated system.”

A team of Northrop Grumman engineers made several field trips to Detroit to see how automakers tackle assembly line automation. “The timing was good, because the auto industry was in the midst of its slowdown when the IAL project kicked off in 2008,” notes Jones.

Engineers from KUKA and Northrop Grumman worked together to design and install a fully optimized assembly line rather than just a conglomeration of independent tooling stations. KUKA leveraged its expertise with high-rate assembly lines, while Northrop Grumman focused on its extensive tooling knowledge.

“That required new thinking,” adds Joel Treadwell, IAL manager. “We had to make fundamental changes to our business model and cast away old methods. For instance, in the past, we used to build at least 80 percent of our tools in-house.”

The IAL required a significant investment and leap in faith for Northrop Grumman. The $100 million project occupies more than 200,000 square feet of space in the temperature-controlled Palmdale plant. It features more than 600 tools and 79 major tool positions.

State-of-the-Art Tools

Airframe assembly tools include automatic laser welding and automated panelization systems, in addition to multifunctional robotic end effectors for drilling, sealant application and fastener insertion. The IAL features 13 articulated robots and an automated guided vehicle (AGV) system.

The increase in automation allows very precise tolerances to be maintained with drilling systems. In fact, one of the highlights of the IAL is a robotic drilling system for inlet ducts. It uses nine-axis robots to drill thousands of holes in a very challenging, small internal space.

A vision guidance system allows the robot to enter the narrow opening in the F-35’s contoured air-inlet ducts, which are critical to the performance of the jet engine.

The composite duct is integrated with the center fuselage by attaching aluminum frames that require hundreds of mechanical fasteners. The assembly process requires the drilling and countersinking of 500 holes per duct. Each air duct is approximately 9 feet long, but only 20 inches in internal diameter.

Despite the ergonomically challenging space constraints, the operation was initially done manually. Assemblers would crawl inside the duct and use hand tools.

By using articulated robots, Northrop Grumman engineers reduced a 52-hour manual process to a 12-hour automated process and also reduced floor space. Three robotic cells drill three different sections of the inlet ducts: aft, forward right side and forward left side. They require 2,000 holes per set.

Because each of the 500 drilling points has a unique safe-radius area, a laser tracking system locates the correct position within a very narrow tolerance. A laser inspection system is also used to evaluate the quality of each hole.

Another highlight of the U-shaped automated assembly line is the fleet of AGVs that transport work in process to assembly cells. Traditionally, overhead cranes are used to move fuselages. However, this creates delays as the crane is acquired, areas cleared for safety, chains and handling fixtures attached, and the subassembly moved.

For example, more than 250 crane moves are required to transport F/A-18 E/F subassemblies through completion at Northrop Grumman’s plant in El Segundo, CA. This is a very time-consuming and disruptive process, because while the move is taking place, work on the plant floor below comes to a halt.

Each move with an overhead crane takes about one hour and requires a crew of up to eight people who help stabilize the fuselage with tethers as it slowly moves from one part of the assembly line to the next. With the AGVs, a similar move only takes about 20 minutes.

“We move the engineering structure and the tool from station to station, because there’s not a jig and fixture at each station on the IAL,” says Hank Reed, director of business development for the F-35 program at North Grumman. “That enhances our ability to keep very tight tolerances. It also reduces flex, improves quality, and greatly reduces the possibility of injuries or accidents.”

Three AGVs have a 38,000-pound capacity, while the other two units can carry 75,000-pound loads. All the vehicles are battery-powered and equipped with obstacle-detection sensors to prevent collisions.

The self-loading AGVs are capable of omnidirectional docking maneuvers. This eliminates tooling misalignments and ensures routing flexibility. It also assures that vehicles interface correctly with various workstation dock designs, which vary in height depending on whether work is being done on the upper or lower section of a fuselage.

The low-profile, height-adjustable AGVs are equipped with inertial guidance technology that enables them to travel along a virtual free-range path rather than follow specific floor tape patterns. This eliminates the problem of blocked lines of sight or targets, and damaged floor tape.

An RFID-based control and indication server continually communicates with servers onboard each AGV. When a vehicle arrives at a workstation, an assembler takes over control. He or she lowers the AGV’s deck, guides the vehicle under a supported tooling structure, and raises the deck to lift the tooling so the fuselage can be moved to the next workcell for further assembly.

Another area where throughput has been improved is in the application of low-observable radar-absorbing coatings, which help give the F-35 its stealth. This time-consuming process was identified as a potential stumbling block in reaching the long-term target rate of producing one fuselage per day.

In the past, the complex process took more than one week using traditional manual methods. By leveraging robotic technology, Northrop Grumman engineers developed an automated process that reduced this to one day.

All IAL cells and the AGVs are integrated together through a central control and indication server. Assemblers use touch-screen terminals to manage all production processes.

People Power

Despite all the recent investment in automation, people play a vital role in assembling the center fuselage of the F-35. For instance, wiring harnesses, pneumatic lines and other components are manually installed.

“The workforce reaction to automation has been mixed, but most people felt that it was a positive departure from traditional assembly processes,” says Reed. “When people saw the benefit in quality and ergonomics, they embraced automation. For instance, by using robots, we’ve been able to replace the need for someone to sit in a hot, cramped inlet duct and drill hundreds of holes.”

Indirect savings from automation incorporated into the IAL line include an 85 percent reduction in lost-time injuries due to the stress of hand drilling. There’s also been a 90 percent reduction in defects and an increase in hole quality.

“We always strive to make jobs easier and safer, so we solicited operator input to improve production processes,” says Reed. “We have a constant feedback mechanism that has resulted in better buy-in. Assemblers remain our most important asset for meeting quality, cost and delivery objectives.”

Northrop Grumman encourages self-directed work teams. In fact, this heritage is derived from Jack Northrop’s personal involvement with his build teams throughout his career.

Every aspect of the F-35 assembly process empowers assemblers to collaborate on product improvement and quality initiatives. For example, self-inspection is critical in controlling the risk of foreign object debris, which is a critical concern in the aerospace industry.

An employee suggestion program provides multiple incentives to provide value and quality to the assembly process. Normal suggestions result in a maximum award of $10,000 based on a percentage of saving derived from the idea. These suggestions are rolled up to an annual savings that is distributed to the entire workforce as a result of a sharing bonus award that amounts to up to two weeks of extra pay.

As an immediate response to spot suggestions, an award process enables managers and supervisors to respond to small improvements within a week with $100 awards.

So far, more than 100 center fuselages have been assembled with the IAL. “We are still in low-rate initial production, building one every five days,” says Reed. “However, once we ramp up to full-rate production in 2018, the goal is to build one center fuselage a day.

“When we get to that rate, we absolutely need to have consistent, repeatable processes,” adds Reed. “Automation gives us that capability.

“Because of the integrated assembly line, we’ve significantly reduced travelled work, in addition to scrap, rework and repair,” claims Reed. “That drives significant cost savings. We expect to see the cost of the center fuselage, and therefore the cost of the entire F-35, come down even further in the future because of automation.” 

About the Award

The Assembly Plant of the Year award was initiated in 2004 to showcase world-class production facilities in America, and the people, products and processes that make them successful. All manufacturers that assemble products in the United States are invited to nominate their plants.

The Assembly Plant of the Year award is sponsored by ASSEMBLY Magazine. The goal of the award is to identify a state-of-the-art facility that has applied world-class processes to reduce production costs, increase productivity, shorten time to market or improve product quality.

All nominees were evaluated by ASSEMBLY’s editorial staff, based on criteria such as:

• Have assembly processes been improved through the use of new technology?

• Has the plant improved its performance by making more effective use of existing technology?

• Has the plant taken steps to reduce production costs?

• Have new or improved assembly processes resulted in increased productivity?

• Has the plant used assembly improvements to reduce time to market?

• Has the plant boosted bottom-line profits and competitive advantage?

• Did operators play a role in the successful implementation of new assembly strategies?

• Has a product been effectively designed for efficient assembly?

• Has the plant attempted to protect the environment and conserve natural resources?

As winner of the 10th annual Assembly Plant of the Year competition, Northrop Grumman’s Integrated Assembly Line in Palmdale, CA, received an engraved crystal award and a commemorative banner.

Reprinted with permission of Assembly, Copyright 2013.