Geometric Optimization of Drills Used to Repair Holes in Magnesium Aeronautical Components

Magnesium alloys are used in the aeronautical sector due to their excellent strength/weight ratios, motivated by the reduction of weight that their use entails. In this sector, drilling is one of the most common operations, if not the most, due to the large number of holes that are used in joining processes, mainly by riveting. The appearance of cracks is a risk to the structural safety of the components, such that it is necessary to regularly check them for maintenance and/or repair tasks. The present study tries to determine the optimization of the characteristics of the twist drills, which are re-sharpened successively to restore the cutting edge after use, as well as the operating parameters in machining. For this purpose, a full factorial experimental design was established, analyzing through the analysis of the variance (ANOVA) the response variables. Surface integrity was considered to carry out a global vision of the quality obtained, covering as response variables the surface roughness, the size of the burrs and the modification of the hardness produced, in addition to a topological characterization by optical means of machined surfaces. The main conclusion is that it is possible that the geometric optimization of the tools and the operating parameters considered in this study in drilling processes allow them to be performed, while maintaining quality and environmental requirements, and at the same time, maximize the productivity of operations.