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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 robotic arm manipulator is often an appealing method to position drills, bolt inserters, automated fiber placement heads, or other end effectors. In a standard robot the flexibility of the cantilevered arm as well as backlash in the drive system lead to large positioning errors. Previous work has greatly reduced this error through the use of secondary scales and a mathematical model of the robot deflection running on a CNC controller. Further research improved upon this model by accounting for linear deformation of each robot link regardless of position. The parameters describing these deformations are determined through a calibration routine and then used in real time to guide the end effector accurately to any reachable pose. In practice this method has been used to achieve total on-part positioning accuracy of better than +/− 0.25mm.

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.

Low rate initial production of the 777X flight control surfaces and wing edges has been underway at the Boeing St. Louis site since early 2017. Drilling, inspection, and temporary fastening tasks are performed by automated multi-function robotic systems supplied by Electroimpact. On the heels of the successful implementation of the initial four (4) systems, Phases II and III are underway to meet increasing production demands with three (3) and four (4) new cells coming online, respectively. Assemblies are dedicated to particular cells for higher-rate production, while all systems are designed for commonality offering strategic backup capability. Safe operation and equipment density are optimized through the use of electronic safeguards. New time-saving process capabilities allow for one-up drilling, hole inspection, fastening, fastener inspection, and stem shaving.

Large diameter, tightly toleranced fastener patterns are commonplace in aerospace structures. Satisfactory generation of these holes is often challenging and can be further complicated by difficult or obstructed access. Bespoke tooling and drill jigs are typically used in conjunction with power feed units leading to a manual, inflexible, and expensive manufacturing process. For 777X flap production, Boeing and Electroimpact collaborated to create a novel, automated solution to generate the fastener holes for the main carrier fitting attachment pattern. Existing robotic automation used for skin to substructure assembly was modified to utilize extended length (up to 635mm), bearing-supported drill bar sub-assemblies. These Long Assembly Drills (LADs) had to be easily attached and detached by one operator, interface with the existing spindle(s), supply cutting lubricant, extract swarf on demand, and include a means for automatically locating datum features.