Dimensional errors of aeronautical casings caused by machining of thin walls and features

• Manufacture of a big-sized thin-walled aeronautical component in real scale (900 mm diameter). • Machining monitoring of 12:1 buy-to-fly ratio component optimizing turning and milling processes. • Harmonic analysis identifies manufacturing, clamping, and geometrical influences on form errors. • Flanges can cause deviations in sections 150 mm away from the machined region. • Honeycomb structures can be used to optimize weight and rigidity without compromising tolerances. Turbofan engines have many components with intricate shapes finished by machining, which induces changes in part rigidity and geometrical deviations. Among them, casings are highlighted by their size, which leads to several hours of manufacturing, incremental tool wear, and challenges related to the clamping fixtures that vie with the tight tolerances required. In casing components, several features are milled, like flanges, which are necessary to join the turbine or compressor stages, and honeycomb structures for weight relief, both magnifying issues related to part stiffness variation. At the same time, the prediction of the process is difficult due to delays associated with unprogrammed stops, machine kinematics, and clamping configuration changes. In this context, a real-scale aeronautical casing was designed and manufactured in XM-12 stainless steel, evaluating manufacturing strategies, times, and deviations. The challenges related to manufacturing its features are detailed as the estimated timeframe, which can increase by 43 % concerning the prediction by the CAM software, affecting the process and costs. Furthermore, the inspection of the casing showed the influence of part geometrical features that resulted in deviation from the characteristic pattern of repetition along the length of the workpiece, with an effect stronger than that of the clamping fixture system.