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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.

Very large multi-axis CNC machines offer a special challenge for efficient and accurate machine compensation. Aerospace applications demand tight tolerances, but conventional compensation methods become expensive for large machines. Volumetric compensation offers an approach for reducing costs and improving accuracies. A unique control architecture enabled by volumetric compensation enables the use of a single part program by multiple machines. Combining multiple technologies (a proprietary volumetric compensation solver program, Spatial Analyzer, API's Active Target, a laser tracker and bespoke CNC-Tracker communication software for measurement triggering) significantly reduces machine compensation time. Available analysis tools also enable the engineer to evaluate measurement uncertainties and determine the best locations for additional stations as well as quantify the accuracy benefits such stations would offer.