Optical Robot Metrology Speeds up Final Inspection of Complex Aerospace Assemblies

Rolls-Royce in Barnoldswick has a long history of using Coordinate Measuring Machines (CMM) for the final inspection of jet engine fabricated assemblies. Order book production rate increases necessitated the need to make a disruptive step-change in inspection methods without increasing the overall production footprint.

Project goals were not only to reduce total inspection time but also to increase available data to enable product design and manufacturing improvements and answer post inspection queries as well as providing data for use in future product developments.

Front Bearing Housings are one of the most complex fabricated assemblies manufactured at Rolls Royce and traditional CMMs have been used for the majority of part inspections complimented with other inspection methods including both manual and visual techniques.

Rolls Royce engineers worked with optical metrology company GOM to review their inspection requirements, including a full review of the 45-sheet drawing, to identify assembly features which could  be captured for inspection optically. Features were categorized into green and red identifying which features were planned to be inspected by the system with selected features tested based upon knowledge, access and tolerances.

The inspection step-change being sought demanded the inspection of the fabricated assemblies in a single set-up. A part fixture was designed and tested virtually prior to manufacture with the virtual review analyzing both design and planned inspection process.

A Measurement System Analysis (MSA) study performed provided the necessary system confidence with observed deviations based upon 5 repeated inspection cycles of Green Features ±0,010mm, Amber Features ±0,015mm with the conclusion that repeatability was acceptable based upon feature tolerance and correlation was achieved against CMM results. Inspection techniques similar to those used by the CMM was performed by the GOM software to aid correlation.

The installed GOM Optical measuring system now performs 70% of the previous CMM inspection tasks in 30% of the time. CMM inspection is still being performed but is no longer the production bottle-neck and overall CMM inspection has been reduced to just 5% of total fabricated part inspection time.

The GOM ScanBox was delivered to Rolls Royce in just 8 weeks; much shorter than the 9 month lead-time typically experienced for a Gantry style CMM. More optical inspection is in the future at Rolls Royce as it seeks to further improve and automate part inspections.

For more information: www.gom.com