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The foundation of many production aircraft assembly facilities is a more dynamic and unpredictable quantity than we would sometimes care to admit. Any tooling structures constructed on these floors, no matter how thoroughly analyzed or well understood, are at the mercy of settling and shifting concrete, which can cause very lengthy and costly periodic re-certification and adjustment procedures. It is with this in mind, then, that we explore the design possibilities for one such structure to be built in Belfast, North Ireland for the assembly of the Shorts C-Series aircraft wings. We evaluate the peak floor pressure, weight, gravity deflection, drilling deflection, and thermal deflection of four promising structures and discover that carefully designed pivot points and tension members can offer significant benefits in some areas.

Serial link articulated robots applied in aerospace assembly have largely been limited in scope by deficiencies in positional accuracy. The majority of aerospace applications require tolerances of +/−0.25mm or less which have historically been far beyond reach of the conventional off-the-shelf robot. The recent development of the accurate robot technology represents a paradigm shift for the use of articulated robotics in airframe assembly. With the addition of secondary feedback, high-order kinematic model, and a fully integrated conventional CNC control, robotic technology can now compete on a performance level with customized high precision motion platforms. As a result, the articulated arm can be applied to a much broader range of assembly applications that were once limited to custom machines, including one-up assembly, two-sided drilling and fastening, material removal, and automated fiber placement.

Once limited by insufficient accuracy, the off-the-shelf industrial robot has been enhanced via the integration of secondary encoders at the output of each of its axes. This in turn with a solid mechanical platform and enhanced kinematic model enable on-part accuracies of less than +/−0.25mm. Continued development of this enabling technology has been demonstrated on representative surfaces of an aircraft fuselage. Positional accuracy and process capability was validated in multiple orientations both in upper surface (spindle down) and lower surface (spindle up) configurations. A second opposing accurate robotic drilling system and full-scale fuselage mockup were integrated to simulate doubled throughput and to demonstrate the feasibility of maintaining high on-part accuracy with a dual spindle cell.

A two machine Automated Fiber Placement (AFP) cell capable of laying 1/2\mi and 1/4\mi tow at rates up to 1800\mi/min (45.7 m/min), including feeds and cuts, has been implemented for the manufacture of large primary aircraft structures. The control architecture of the cell is such that part programs are machine independent and can run on either machine or simultaneously on both machines at the same time. A Central Cell Controller pushes part programs to each AFP machine and coordinates the cell. Volumetric accuracy of the two machines is under 0.008\mi (0.2 mm) radial error in the entire compensated envelop, which is approximately 64' x 21' x 14' (19.5 m x 6.4 m x 4.3 m) for each machine. This is accomplished through optimization of volumetric kinematic compensation parameters using a linear numerical solver. The machines reference a common coordinate system which allows great flexibility in part programming.

Electroimpact has recently produced a high-speed fuselage panel fastening machine which utilizes an all-electric, CNC-controlled squeeze process for rivet upset and bolt insertion. The machine is designed to fasten skin panels to stringers, shear ties, and other internal fuselage components. A high riveting rate of 15 rivets per minute was achieved on the first-generation E7000 machine. This rate includes drilling, insertion, and upset of headed fuselage rivets. The rivets are inserted by a roller screw-driven upper actuator, with rivet upset performed by a lower actuator driven by a high-load-capacity ball screw. The rivet upset process can be controlled using either position- or load-based feedback. The E7000 machine incorporates a number of systems to increase panel processing speed, improve final product quality, and minimize operator intervention.

Electroimpact's newest riveting machine features a track-style injector with Bomb Bay Ejection Doors. The Bomb Bay Ejection Doors are a robust way to eject fasteners from track style injector. Track style injectors are commonly used by Electroimpact and others in the industry. Using the Bomb Bay Doors for fastener ejection consists of opening the tracks allowing very solid clearing of an injector when ejecting a fastener translating to a more reliable fastener delivery system. Examples of when fastener ejection is needed are when a fastener is sent backwards, when there are two in the tube, or when a machine operator stops or resets the machine during a fastening cycle. This method allows fasteners to be cleared in nearly every situation when ejecting a fastener is required. Additional feature of Electroimpact's new injection system is integrated anvil tool change.

Manufacturing C cross-sectional components with high aspect ratios out of carbon fiber reinforced composites is desirable by the aircraft industry. Modular AFP heads with short, fixed tow path have the fundamental performance characteristics required to successfully and productively automate the production of these part families. Aircraft parts in this family include wing spars, stringers, and fuselage frames.

Wing and fuselage aircraft structures require large precise tools for assembly. These large jigs require periodic re-certification to validate jig accuracy, yet metrology tasks involved may take the tool out of service for a week or more and typically require highly specialized personnel. Increasing the time between re-certifications adds the risk of making out-of-tolerance assemblies. How can we reduce jig re-certification down time without increasing the risk of using out-of-tolerance tooling? An alternative, successfully tested in a prototype tool, is to bring automated metrology tools to bear. Specifically, laser tracker measurements can be automated through a combination of off-the-shelf & custom software, careful line-of-sight planning, and permanent embedded targets. Retro-reflectors are placed at critical points throughout the jig. Inaccessible (out of reach) tool areas are addressed through the use of low cost, permanent, shielded repeatability targets.

Design and production of an assembly system for a major aircraft component is a complex undertaking, which demands a large-scale system view. Electroimpact has completed a turnkey assembly line for producing the wing, flap, and aileron structures for the COMAC C919 aircraft in Xi’an, China. The project scope includes assembly process design, material handling design, equipment design, manufacture, installation, and first article production support. Inputs to the assembly line are individual component parts and small subassemblies. The assembly line output is a structurally completed set of wing box, flaps, and ailerons, for delivery to the Final Assembly Line in Shanghai. There is a trend toward defining an assembly line procurement contract by production capacity, versus a list of components, which implies that an equipment supplier must become an owner of production processes.

Flex Track Drilling systems are being used increasingly in aerospace applications providing low cost, highly efficient automated drilling systems. Certain applications like circumferential splice drilling on large size airplane fuselages require multi spindle flex track systems working in tandem to meet production efficiency requirements. This paper discusses the development of a multi spindle flex track drilling system for a circumferential splice drilling on the 777 airplane. The multi spindle system developed uses a variety of flex track carriages attached to the flexible vacuum tracks to allow for offset or wide inside drilling. Segmented machine programmes allow these multiple machines to be deployed on the same circumferential splice on the airplane providing the multi spindle system. Interfacing of the multiple spindles is achieved by a custom OEM interface using a single screen thereby ensuring simplicity of operation.

Boeing has relied upon the 767 ASAT (ASAT1) since 1983 to fasten the chords, stiffeners and rib posts to the web of the four 767 wing spars. The machine was originally commissioned with a Terra five axis CNC control. The Terra company went out of business and the controls were replaced with a custom DOS application in 1990. These are now hard to support so Boeing solicited proposals. Electroimpact proposed to retrofit with a Fanuc 31I CNC, and in addition, to replace all associated sensors, cables and feedback systems. This work is now complete on two of the four machines. Both left front and right front are in production with the new CNC control.

Electroimpact has designed the E6000, the next generation riveting machine, with a focus on reduced weight and speed. It will initially be used on ARJ21 wing panels in Xi'an, China, but it is able to fasten a variety of panels including A320 and 737. The E6000's fastening cycle is capable of forming and shaving 16 rivets per minute. Head alignment is maintained by two independent four axis heads using a combination of controls and kinematics. Process tool speed has been improved via high lead screws, high speed Fanuc motors, and a shorter head stone drop. An innovative EI operator interface enhances end user experience.

Electroimpact revisited a piece of automation history this year. In 1989, Electroimpact delivered its first ever Automated Electromagnetic Riveting and Assembly Cell or A.E.R.A.C. to Textron Aero Structures, now Vought Aircraft Industries. These machines produce upper wing panels for Airbus A330/340 aircraft. They were the precursor to the Low Voltage Electromagnetic Riveters or LVER's producing wing panels for Airbus single isle, A340 and A380 programs in Broughton, Wales, UK. In 2009, Electroimpact delivered two next generation AERAC machines to Vought Aircraft Industries. A significant design challenge was to hold the moving mass for the entire machine under 5220 kg without sacrificing performance of the LVER. These machines employ several new technologies to achieve this including Electroimpact's latest generation rivet injector, an integrated headstone load cell, and GE Fanuc's customer board.

Airbus UK was interested in a high-speed riveting machine cell that could automatically rivet over 30 different wing panels for a wide range of aircraft to fit in a limited floor space. Electroimpact was approached and proposed a Flexible, High Speed, Riveting Machine (HSRM). The resulting flexible riveting cell is 170 feet long and contains two flexible fixtures located end to end. Two fixtures allow manual work on one fixture while the machine is riveting on the second fixture. Each fixture can be quickly reconfigured to accommodate a broad range of Airbus panels. The system went into production on January 12, 2003 and has been extremely effective, riveting the first wing panel, a lower panel 1 for the A330-300 in only 5 days. This was one of the largest panels the cell was sized to accommodate. Anticipated process improvements will reduce the riveting time to just three days per panel.

The ONCE robotic drilling system utilizes a mass produced, high capacity industrial robot as the motion platform for an automated drilling, countersinking, and hole inspection machine for the skin to substructure join on the F/A-18E/F Super Hornet wing trailing edge flaps (TEF). Historically, robots have lacked the accuracy, payload capacity, and stiffness required for aerospace drilling applications. Recent improvements in positional accuracy and payload capacity, along with position and stiffness compensation, have enabled the robot to become an effective motion platform. Coupled with a servo-controlled multifunction end effector (MFEE), hole locations have successfully been placed within the specification's +/-0.060″ tolerance. The hole diameters and countersinks have proven to be very accurate, with countersink depth variation at 0.0025″ worst case.

Automated collar and nut installation requires complex hardware on the wet side of the spar or wing panel. Wet side automatic tool changers are becoming common but an operator is often required to connect electrical, pneumatic and fastener feed system components. This is unacceptable in a lights-out cell, and any fully automatic solution must be reliable while satisfying demanding design requirements. Figure 1 Wet side anvil for nut installation. The 737 Spar Assembly Line (SAL) is a new lights-out machine cell at the Boeing factory in Renton, Washington. The SAL machines are equipped with a unique fully automatic tool changer (ATC). The wet side ATC interface is designed to automatically connect conventional as well as more unique services such as fastener feed. The fastener feed ATC module, called the “spinner,” rotates with the machine’s wet side rotary axis (C axis). It consists of a stack of rotors that rotate inside of a stationary annulus.

Electroimpact and Lockheed Martin have developed an automated drilling and fastening system for C-130J aft fuselage panels. Numerous design and manufacturing challenges were addressed to incorporate the system into Lockheed Martin’s existing manufacturing paradigm and to adapt Electroimpact’s existing line of riveting machines for manufacture of these legacy aircraft parts. Challenges to automation included design of a very long yet sufficiently rigid and lightweight offset riveting anvil for fastening around deep circumferential frames, automated feeding of very short, “square” rivets in which the length is similar to the head diameter, creation of part programs and simulation models for legacy parts with no existing 3d manufacturing data, and crash protection for the aircraft part from machine collisions, given the uncertainties inherent in the model and the unique geometry of the aircraft parts.

The Electromagnetic Bolt Inserter (EMB) is a new tool that combines functions that on previous machines were performed by two tools, a bolt inserter followed by an EMR. By combining the operations of two tools in one the processing time for the wing spar is reduced. The tool incorporates quality checks for bolt length, stake height and bolt insert height.

As part of a Composite Wing Manufacture Program, Electroimpact was asked to design and develop a small portable milling machine for machining CFRP. The machine needed to be light so it could be lifted by two operators, robust to the production environment, and stiff enough to allow it to cut a 15 mm deep 3/8\mi slot through composite material (CFRP), in one pass, with no delamination. The machine also needed to be capable of performing a 30 mm deep finishing cut, in one pass, with 3 μm or better surface finish. Specialist Polycrystalline Diamond (PDC) roughing cutters were developed for the cutting process to reduce cutting loads and vibration while maximizing cutter life. The machine also needed to be capable of cutting along a 2 axis path. Electroimpact successfully introduced the machine in to the production environment in October 2011, within a 12 month development window.

Electroimpact's E4000 LVER riveting machine entered service in 1998 assembling A320/A321 upper wing panels at the Airbus wing manufacturing facility in Broughton, Wales. Airbus's recent introduction of the Sharklet modification to the wings of the A320 family of aircraft necessitated a number of changes to the machine and fixture to accommodate the revised wing geometry. Electroimpact and Airbus also worked together to identify a wide range of machine improvements and updates. A short list of the changes made to the machine includes a new CNC, new motors, scales, spindles, and new technologies such as laser tracers and normality sensors. The end result is a faster, more accurate machine with state-of-the-art controls ready to support Airbus's A320/321 wing panel assembly for the next 15 years.