- SPECIAL REPORTS
Traditionally, aircraft are assembled with large gantry machines. For instance, Vought Aircraft Industries Inc. (Irving, TX), uses an automated drilling and fastening system from Brotje Automation GmbH (Wiefelstede, Germany) to produce fuselage assemblies for the Boeing 787.
“Large skin panels are loaded into the workcell,” says Martin Wimmer, Vought’s R&D manager. “The panel and machine are indexed. The machine then moves around the panel, drilling holes and installing fasteners per print.”
Similar equipment is used to manufacture military aircraft. “Automated gantry systems drill, ream and countersink about 85 percent of the external holes on the F-35 Joint Strike Fighter,” claims Dr. Don Kinard, technical operations deputy for F-35 global production operations at Lockheed Martin Corp. (Bethesda, MD). “High-tolerance gantry systems are used to machine component assemblies and detail parts to eliminate shimming at assembly and control the aircraft outer mold lines.”
Unfortunately, gantry machines are expensive. And, they typically have limited throughput and require a large footprint. Unlike gantry systems and other large, heavy pieces of fixed automation, robots are more flexible, less expensive and can be quickly deployed.
“The current manufacturing solution relies on the manual assembly of components using complex jigs and expensive, product-specific fixtures,” says Phil Webb, an associate professor in the School of Mechanical, Materials and Manufacturing Engineering at the University of Nottingham (Nottingham, England). “The application of robotics to the assembly of large aerostructures has been limited by the large size and inherent compliance of the components involved.”
During the last decade, Webb and his colleagues have worked with manufacturers such as Airbus Bombardier and Rolls-Royce to develop robots for use in the aerospace industry. “The benefits of using robots for aerospace manufacturing includes cost reduction, process repeatability, head count reduction and a reduction in jig-fixture requirements,” explains Webb. Other advantages over fixed automation include increased uptime, reduced scrap and reduced maintenance costs.
To assemble aircraft fuselages, custom-designed machinery traditionally must be used to provide the required accuracies. “In many cases, this type of equipment has proven cost-prohibitive, especially for lower-volume manufactures in the general aviation field,” notes Rush LaSelle, general manager of western operations at FANUC Robotics America Inc. (Rochester Hills, MI). “The adoption of industrial robots [in the aerospace industry] is only in its infancy. The area where we anticipate the greatest growth is with smaller aircraft manufacturers that have historically been priced out of custom-designed automated drilling and fastening equipment.
“We see the general aviation segment as a substantial growth area,” LaSelle points out. “Given the cost effectiveness of utilizing robotic systems in conjunction with or in place of custom equipment, smaller manufacturers are beginning to gain access to technology that five years ago was only affordable for the largest commercial and military manufacturers.
“With developments over the past few years using secondary servo feedback, [we are] capable of providing robots with reaches of over three meters with global positional accuracies of 0.01 inch, which is on par with conventional CNC equipment,” adds LaSelle. “This will act as enabling technology for many aerospace manufacturers.
“With the 100 percent inspection requirements mandated by governing bodies [such as the Federal Aviation Administration], aerospace manufacturers are also adopting vision at an increased rate to inspect and report production parameters,” claims LaSelle. “Vision [technology] helps offset some of the challenges created by short runs and small volume, and its impact on financially justifying automated equipment.”
According to LaSelle, one or more robots can replace a custom-designed machine in approximately one-fourth the amount of time, which represents significant value to aircraft manufacturers. “Not only does the lead-time shrink tremendously when industrial robots are employed, so too does the cost of the system,” he points out. “Robots cost a fraction of a custom-designed machine; in one account, a robotic solution was less than half the cost of the alternative.”
Engineers at the National Research Council of Canada’s Aerospace Manufacturing Technology Centre (Montreal) are using robots to develop low-cost, flexible approaches to aerostructure assembly. “Because of robots, there is a move in the aerospace industry away from large monuments,” says Claude Perron, group leader of automation and robotics.
Perron and his colleagues recently developed a robotic airframe riveter for Bombardier. The system, which uses two robots and infrared vision technology, resulted in a 50 percent reduction in cycle time.
The Canadian engineers are currently developing robotic fiber placement and friction stir welding systems to replace traditional fixed automation. “With robots, we can automate assembly processes at about one-tenth the cost of gantry systems,” claims Perron.