Turbines housed in aircraft engines are subjected to some of the roughest conditions imaginable. They are pieces of mission-critical equipment that must perform flawlessly at speeds of 30,000 RPM in temperatures greater than 800°C for hours at a time.

Therefore, engine manufacturers fully understand that even small surface defects can reduce performance, increase maintenance costs and reduce the useful life of an aircraft engine. They need to inspect turbine blades very carefully to maintain the efficiency and reliability that the air transport industry requires.

One particular North American manufacturer inspected its blades by hand and human eye. The highly trained inspectors would measure hundreds of features and check for surface defects at depths in the order of thousandths of an inch. Manual inspection was not only costly, in terms of time and labour, but it was subjective as well. Results were variable and even differed between inspectors. Finally, because manual inspection was so time consuming, there was no systematic inspection of every blade; only a sampling of blades would be inspected. Clearly, the manufacturer required an approach that would allow systematic inspections of the blades, save time, and yield consistent and repeatable results.

That was when they approached Orus Integration Inc. in Laval, Que., to design an automated turbine inspection system. Project manager Louis Dicaire says that early on in the project, the development team learned that flexibility, repeatability and precision were absolutely necessary for success. During development, the Orus engineering team relied on their previous experience — they designed vision-based metrology systems for the Canadian military and aerospace industry. They also worked closely with Genik Automation in St. Jérôme, Que., for part handling and mechanical engineering of the machine.

Orus calls the system the INL-1900x2T. A single enclosure houses two stations that perform the inspections. The metrology station features two Basler GigE cameras at 1920x1080, each fitted with a large field of view telecentric lens (non-perspective lens) and two collimated LED blue (520 nm) lights. The surface inspection station uses four Basler GigE cameras; the resolution of the first camera is 1920x1080 for the surface inspection, and the remaining three offer a 640x480 resolution for surface inspection of areas that are hard to reach with a single camera. Two CCS diffuse on-axis lights and one CCD diffuse backlight illuminate the surface station. A Fanuc six-axis LR Mate 200iC robot and 4U controller and Omron PLC round out the hardware components. The software is based on the Matrox Imaging Library 9.0 with Processing Pack 1.