QMT Features: September 2014
Enhanced turbine blade measurement
A new system allows 100% visualisation of every blade

The highly complex form and geometry of aerospace turbine blades have long posed problems when it comes to the efficient measuring and recording of its profile and surface quality. With traceability a vital requirement in their manufacture, Mahr has now developed a system that will allow 100 per cent visualisation of every blade produced.

Due to extended measurement time using existing methods, it has been impossible to place blade measurement technology into the production line. With the new MarSurf FP 40/180 optical 3D-scanner system from Mahr, which uses two scanners and a fixed sensor, along with its Geomagic Qualify software, scanning times are now as short as 25-30 seconds, meaning that in-line measurement of these complex forms is now a possibility.

Developed in partnership with Germany’s Fraunhofer Institute for Applied Optics and Precision Engineering (IOF), the MarSurf FP 40/180 is a contactless system that measures the form deviations and dimensions of any object in its field of view using the fringe projection method.

The two scanners have 40 mm and 180 mm fields of view and can measure up to 1.5 million points per position during a scan. After the turbine blade is positioned on the measuring table, an image of the part is made according to the pre-set measurement plan, in which the sensor positions (number of views) and the sensor settings (mirror tilts) are stored. All of this is carried out fully automatically with the resulting measured points recorded at the positions defined in the measurement plan and stored in ASCII format.

This information is then analysed using the Geomagic Qualify software to provide a comprehensive evaluation of form deviation (if CAD file is available), detection of surface defects, and dimensional accuracy among other elements.
When a CAD file is available the 3D point cloud generated by the Geomagic Qualify software can be evaluated and analysed in much greater detail. For example, shape deviations between the measured values and the 3D CAD model are output as a colour-coded image, with additional analysis such as shape and position tolerances also integrated into the process. With Mahr’s optional Geomagic Studio software this 3D scan data can then be converted into highly accurate surfaces, polygon and native CAD models.

“This development of non-contact, high speed, measurement of complex forms, opens up many possibilities across a wide range of industrial sectors, not just aerospace,” says Jonathan Firnberg, Managing Director, Mahr U.K.

“The ability to scan and process data within the production environment and deliver up to 100% visualisation is a major breakthrough. We are confident that it will generate lots of interest within the UK. As such, we will be installing a system at one of the UK’s High Value Manufacturing Industrial Catapult sites in the very near future, so that it will be available to a wider audience for appraisal purposes.”


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