The history of Nikon Metrology (formerly Metris) with metrology-assisted production goes back seven years. “We first developed integrated laser systems that included metrology for composite material layup and verification. That system grew into a guidance tool for manual assembly processes,” says Jarrad Morden, general manager of Nikon Metrology Canada. Their custom-built, integrated systems use various metrology instruments, including Nikon Metrology’s indoor GPS (iGPS) technology, to align one or more laser projectors precisely to a part, tool, or surface.
Building on that experience, Morden sees three distinct areas for future growth of advanced metrology applications in aerospace: metrology-assisted production, metrology-assisted assembly, and fully automated inspection solutions. “Automated inspection solutions offer significant benefits in reducing inspection time on part and assembly conformance checks,” says Morden. The traditional manufacturing process—still relevant despite gains in metrology-assisted production—means adding value to a part, then inspecting it before shipping. “In the large-scale, aerospace world, that end-inspection process has typically been a manual process using products like tracking interferometers, photogrammetry, theodolites, or total station networks,” explains Morden. These precision metrology tools require human operators and, of course, humans introduce variability. He points to automated measurement tools like Nikon Metrology’s laser radar and iGPS localized instruments as a way to mitigate human variability. “We are able to fully automate a measurement plan that can be run lights-out. The trend in the industry, of course, is to move as much of that inspection upstream into the manufacturing process as possible, so that dimensional quality is built in, reducing or eliminating end-process inspection.” He describes this as a clear industry trend that will evolve slowly over time.
Coupled with this development is the growing interest in using robotics for aerospace manufacturing applications, asserts Morden. Robots are repeatable, reliable, and cost-effective when compared to custom or hard automation. While often repeatable to submillimeters, they are not necessarily accurate enough to program to drill or machine to aerospace tolerances using standard off-line programming tools. Other variables matter as well. “Under varying load conditions and clamping forces, which often happens with tool changes, end effectors [on a robot] can lose accuracy relative to the workpiece,” Morden explains.
Enter the Adaptive Robotic Control (ARC) system, a result of a two-year research program that involved Airbus UK (Broughton, UK) and Kuka Robotics (Augsburg, Germany). It combines a Nikon Metrology K-Series Optical CMM device with a Kuka robot. The metrology system feeds position data directly into the robot controller. Morden points out three important capabilities of this system: it verifies each position before a drilling or trimming operation; it’s programmed off-line with standard robot programming packages using Catia CAD models of the parts; and it delivers accuracy independent of robot wear, temperature variations, or load variations. The system has been used at Airbus for two years, and Nikon Metrology reports no rejected parts in that time. A system delivered to Bombardier (Montreal, QC) also has had no reports of rejected parts after a year of use. Integration of the many, sometimes disparate elements of metrology available is the key to growth of metrology-assisted manufacturing, according to Morden.
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