Lightowler from Nikon has seen interest in robotics for aerospace for a few years now, generally as a replacement for fixed purpose-built automation. He believes aerospace manufacturers see them as being cheaper, more flexible, and quicker to deploy. While robotic replacements for monolith or gantry-type machines have been tried, they have met varying degrees of success, according to Lightowler. “One issue is accuracy,” he said. Robots by themselves struggle to achieve aerospace tolerance accuracy, about 0.2 mm, even with cali- bration or error mapping.
radar, such as the Nikon ModelMaker MMDx, and perform in- line inspection. The guided portion of the drilling used a Nikon K-Series sensor with Nikon’s Adaptive Robot control (ARC) software on a Fanuc R1000iA 80Kg payload robot. “Inspec- tion stations are quite often away from the manufacturing area and overloaded. In-process measurement offers benefits in time, quality, and logistics,” Lightowler explained. The motivation? “Our customers were losing work to companies taking advantage of low-wage areas of the world,” Lightowler said. Feasibility studies showed a combined robotic operation could save a vast amount, allowing them to keep the work in the UK.
Beyond that, he notes that they are currently developing two projects that include not only guiding and inspecting, but performing adaptive machining as well. “Another task we are doing for an aircraft engine manufacturer is to scan parts that they know are going to vary, create a reverse engineering model if you will, and adaptively machine those parts based on that information,” said Lightowler. This eliminates the need to try to develop machining programs from a nominal CAD model alone; the scan allows for precise, adaptive machining of parts from as-built.
Metrology and the Monoliths
A robotic drilling system (below), guided by a laser tracker, enabled replacing difficult manual drilling (above) in the inlet section of the F-35.
“What we are looking at is taking robots guided by metrolo- gy into smaller parts, replacing manual operations rather than trying to compete with the big, [purpose-built] machines,” explains Lightowler. They are developing a lightweight drilling concept as part of a project for GKN Aerospace that allows the robot to drill (guided) holes, then swap the head out for a laser
Another task that can require highly skilled metrologists is the periodic recertification of assembly tooling. Like others, Electroimpact (Mukilteo, WA) uses metrology to compensate for machine tool motion, say during drilling and fastening operations. The company also delivers tooling fixtures used to mate aircraft sections together. These, too, can be a drain on resources skilled in metrology, albeit periodically. “When you build a jig initially, you measure it precisely before going into production,” said Robert Flynn project manager of Electro- impact. “However, once in production, you cannot ignore its measurement and tolerances—issues occur.” Minor mishaps, such as a bump with a heavy tool or a glance with a forklift, could cause a misalignment. With tolerances so tight, between 0.010 and 0.007" (0.254 and 0.178 mm), production crews may not notice. So, it is recertified periodically, anywhere from six months to two years, according to Flynn. “The downside is that re-certs can take tooling out of production for a few days to a few weeks, and it requires specialized technicians,” said Flynn, two cost items airframe manufacturers need to reduce. In response, the company created an automated system for tooling recertifications. They used a combination of existing