Survey of the inside of a number of tapering carbon fibre wingbox segments
Dual laser inspection of a carbon fibre wingbox using a crawler for navigation in less than one hour per segment
One-off special design to measure the critical stress concentration points
Highly accurate and repeatable measurements fit for one the world’s largest plane manufacturers on their most advanced plane, the Dreamliner
Full data management using the collection software, providing the customer with CAD models
We were approached by an aerospace organisation to tackle a particularly tricky problem to survey the inside of a number of tapering carbon fibre wingbox segments that ranged in size from around 100 mm square, up to 700 mm x 500 mm over a distance of 12 metres. The accuracy of the survey had to be within 0.25 mm. A requirement was to measure the shape of cross-sections of the structure at regular intervals, then stitch these segments together to provide a CAD model of the inside spaces of the entire tail plane of a Boeing Dreamliner. Of course, a survey had to be achieved in less than an hour per section. Our task was to start again and produce a ‘professional’ version, fit for one the world’s largest plane manufacturers on their most advanced plane, the Dreamliner.
One of the key tasks was to accurately measure the corner radii of the box wing sections, which are absolutely critical as these are stress concentration points.
The solution was to make use of the accuracy of laser triangulation devices and to co-ordinate each measurement into the frame of reference of a laser tracker. At the same time the device had to maintain itself central in the structure both horizontally and vertically.
1. Steer the inspection unit using crawler tracks. The device has to ‘drive’ along a flat carbon fibre composite structure, being steered to keep the tool central in the structure.
2. Keeping the tool in the middle of the structure. It was necessary to ensure that the device would remain in the centre of the structure over a 12 metre distance. Laser ranging sensors on either side of the device at both the front and back.
3. Keep the laser head centralised. A parallel motion system was designed which enabled the measurement head to be raised and lowered.
4. Measure a rectangular structure of varying size. Three different heads were made to address the ranges required. One of the heads required two lasers sensors, in order to obtain the accuracy and range required.
5. Determine the spatial position of each measured cross-section. A laser tracker measured the location of the tooling ball as it travels through a circle in space. As a consequence, not only the location of the centre of the measurements was determined by the centre of the circle, but also the distance from the laser tracker and its position in space. The resulting information was then fed directly into a software package which was able to collect all of the measurement data ready for storage and analysis.