Improving of the hole drilling process for metal composite combinations at aerospace industry

In this study, the effect of drill geometry and cutting speed on hole quality and cutting performance in manual and automatic drilling operations performed on composite and composite / metal stack structures by covering the entire drilling process during the assembly phase in the aviation industry was investigated. Studies were carried out in four stages. In Phase-1, three new drill geometries developed for this study and commercially available drill geometries were compared experimentally according to the hole diameter, cylindricity and delamination data. In Phase-2, three drill geometries developed for testing on composite / metal stack were compared experimentally according to the hole diameter, surface roughness, delamination and tool wear data. In Phase-3A, three different cutting speed values (51 m / min, 94 m / min, 163 m / min) by using Type-A drill were compared experimentally according to the hole diameter, circularity, cylindricity, and surface roughness data. In phase-3B, the holes drilled at 94 m / min cutting speed were compared experimentally according to the hole diameter, circularity, cylindricity, surface roughness, tool wear and delamination data. Experimental results were evaluated using variance analysis and process capability analysis. The studies were carried out to analyze the whole drilling process with pneumatic portable equipments used during the assembly operations. As a result, the importance and effect rates of different approaches on the test results in determining the drill geometry and optimum cutting speed in drilling operations during the assembly were revealed. It was observed that the newly developed drill geometry no 17 in Phase-1, Type-A drill geometry in Phase-2, cutting speed of 94 m / min in Phase-3A yielded more successful results. With the work in Phase-1, the drilling time has been reduced from 1.5 minutes per hole to 1 minute per hole. According to the results of 30 holes drilled in Phase-3B, it was observed that the process capability index values for Type-A drill and 94 m / min cutting speed were higher than 1,33.