Affordable automation for airframe assembly : developing of key enabling technologies

Abstract: Building aircraft is a challenging field. An aircraft has a life expectancy of 40 years, compared to just 10 years for a car. Given the vibrations of flying at close to Mach one at an altitude of 10,000 meters, these machines must function flawlessly in a tough environment. This demands high quality in the assembly processes. The typical part joining process in the automotive industry is welding, whereas in the aircraft industry, assembly is made through drilling, followed by fastening. The typical tolerances for part location in aircraft assembly, as well as for hole drilling, is +/- 0.2 mm.This dissertation discusses the use of industrial robots, widely used for welding and pick-and-place operation for automotive industry, in the automation of the aircraft industry, and specifically for the drilling of holes in the assembly process of airframe parts. The dissertation presents how a new drilling technology called orbital drilling is incorporated with and industrial robot. Orbital drilling reduces the cutting forces up to ten times compared to conventional drilling using a spiral cutter.The robot is also utilized for performing changeovers between different airframe structure types. A novel jointed reconfigurable tooling system called Affordable Reconfigurable Tooling (ART) is presented, which uses the robot to reconfigure flexible fixture modules. The ART system can also be rebuilt, which means that the tool is dismantled and reused for a completely different product family (e.g. wings, fins or fuselage sections). This is made possible through a modular framework, i.e. not welded as with conventional tooling, but rather jointed by screws.Robots, originally developed for the automotive industry, have an accuracy which is ten times less accurate than that required for aerospace applications. To help meet this limitation in the use of robots in aircraft assembly, an additional metrology system, used in the aircraft industry for calibrating assembly tooling, is integrated into the robot controller. The feedback loop enables the robot to be positioned to ±0.05 mm absolute accuracy. This integration is made possible by existing embedded software packages for the robot and the metrology system.The processes in the system are programmed in a software package with an intuitive user interface in a 3D-environment, normally used for the offline-programming of robots in automotive industry. The planning is intuitive, and an approach towards a process planning abstraction level is presented where processes are defined directly on the coordinate frames constituting the robot trajectories and manual operations. Tolerance on accuracy requirements are dynamically programmed in the same environment. The metrology system, working online with the robot controller, eliminates most of the calibration work required in traditional robot programming. Changes in the operation planning take less than a minute to run physically with the best tolerance.