Optical Metrology Supports Airfoil Manufacturing and Repair Processes

07/2016ATOS fringe pattern projection systems are ideally suited for the quality control of complex freeform surfaces and thus are used to inspect airfoils of aircraft engines, terrestrial gas & steam turbines and turbocharging systems.

Optical metrology has proven its effectiveness for fan blades, compressor blades and vanes, stator assemblies, blisks and drums, nozzle guide vanes and turbine blades.

Many airfoils are manufactured in process chains based on casting, forging, milling and grinding. In quality control, the optical ATOS 3D scanner supports the introduction of new products as well as the inspection and final acceptance in various production technologies. ATOS measures highly complex geometries, freeform surfaces and application-specific inspection features efficiently and precisely. Color deviation maps, 2D and 3D analyses of shape, position and thickness help to quantify manufacturing effects. A particular advantage of the optical and full-field component inspection is that it requires only a fraction of the time taken by tactile systems. For forged airfoils, ATOS is mainly used for the measurement of forging dies and resulting products. This step particularly serves the quality control of compressor blades and vanes, in order to accurately determine the thickness and profile tolerances. In addition, ATOS has proven its efficiency in checking wear and for repair methods for forging dies during forming and forging process chains.

Adaptive Manufacturing with ATOS Measuring Data

A number of new manufacturing and repair processes have emerged from the combination of high-resolution 3D measuring data and adaptive CAD / CAM technologies. ATOS can be used, for example, to measure the stock material of forged and cast components. The ATOS 3D measuring data serve as a basis for CAD / CAM programs to compute the best alignment and CNC machining path and to produce the airfoil this way.

Seamless Surface Repair

In maintenance, repair and overhaul (MRO), ATOS is used for repairing components. For this purpose, the ATOS data serve to localize the damaged areas. Analyzing the 3D measuring data and with the help of CAD / CAM programs, the optimal tool paths can be computed to prepare the damaged area as well as to apply and blend the repair material in order to make the component serviceable again.

Specific Airfoil Software Features

The alignment and 2D section inspection features provided in GOM Inspect and GOM Inspect Professional include all typical airfoil measurement requirements. Besides the standard inspection functions and the application-specific alignments, such as “6 Point Nested” and “Balanced Beam”, the user can create customized measuring principles for individual inspection tasks. Due to the customized inspection principle, the software significantly simplifies the workflow in projects with multiple inspection sections. Key features are the profile mean line method and the inverse skeleton line method, which serve to determine the thickness based on the camber line perpendicular to the section. In addition, the software includes functions to check profile edge circles or the maximum profile thickness as well as cone-based sections and the evaluation of profile twists.

Since the introduction of the automated ATOS measuring technology in 1999, GOM has developed a number of technologies that have resulted in ATOS being increasingly used for the final inspection of airfoils: ATOS ScanBox, Virtual Measuring Room, automated photogrammetry and Kiosk Interface. These tools allow users to create robust processes with levels of measurement uncertainty that meet the requirements for airfoil inspections.

However, ATOS owes its success in the airfoil inspection to its speed compared to conventional tactile measuring methods. Detailed airfoil inspections can be realized in half the time required by conventional technologies. The section-based tactile 2D inspection of airfoils that has been prevalent so far, will in future be replaced by optical full-field measuring techniques guaranteeing a 3D airfoil inspection.