While being a common manufacturing process in the aeronautics industry, finding the right tools and parameters for drilling in composites remains a challenge. In today’s production, quality of the bores is ensured by keeping the drilling process within tight process tolerances, after qualification of the process via destructive testing.
The extended use of carbon fiber composite parts in aircraft construction (e.g. Airbus A350) requires improved process technologies for the drilling of holes in carbon fibre composites. For the assembly of hull components more than 10.000 holes need to be drilled. The quality of the drilling is important, because it has impact on the mechanical strength of the parts, when they are assembled using fasteners (rivets) that are inserted into the holes. Existing methods focus on the entry and exit area of the drilled area outside of the hole. If defects (especially delaminations) are detected in this area, ultra-sound is used for further inspection. The inner surface of the holes, however, is currently not inspected. Experiments with roughness measurement systems did not lead to conclusive results, because the inhomogeneous surface texture of carbon fiber materials inside the hole, does not lead to useful results, when standard roughness measurements are used. Consequently, better methods for assessing the inner surface of drilled holes are required.
This HScan project developed a machine-vision-based inspection tool for the inspection of the inner surface of bores. The sensor works with an endoscope equipped with light sources that allow illumination from eight different angles. The inspection result is based on set of quality criteria, Rating the Surface Quality and defects.
