Analysis of the Tool Deflection in End Milling of Titanium

The world’s increasing demand for intercontinental mobility is leading to a steady growth in aircraft sales, with Airbus forecasting a total demand for 32,600 passenger aircraft until the year 2034. However, this demand arises not solely due to increased passenger numbers but also due to the need of replacing current aircraft as a consequence of their increasing service life. Since fuel consumption accounts for about one-third of operating costs, airlines need efficient jet engines to meet reduced noise emissions and fuel consumption demands in order to withstand international cost pressures. The development of new aircraft types focuses on the aspect of weight reduction. The aerospace industry is characterized not only by innovations in material science and technology, but also by increased integral construction of individual components for the sake of weight reduction. Integral components are characterized by deep cavities and consist of difficult-to-cut materials to achieve weight reduction, presenting challenges for manufacturing technology. The most commonly encountered manufacturing technology for integral components is high performance cutting (HPC), using tools with a large overhang, whereby the process chain consists of two stages: roughing and finishing. However, manufacturing of integral components pushes HPC milling to its productivity limits. The interaction between work piece and end mill in the form of radial cutting forces leads to tool deflection and therefore limits the manufacturing of deep cavities. The present experimental study contributes to the analysis of tool deflection in the end milling of integral components, e.g., a blade integrated disk made of titanium for the aerospace industry. The goal is to identify and describe tool deflection during milling and to analyze its interdependence with form deviation, as well as the local and global tool load. A dynamometer is used to measure the global load on the tool and an experimental setup is designed and implemented to measure tool deflection and to identify the influence of the tool holder on total tool deflection. To determine tool deflection, the tool’s stiffness is determined by a reference measurement. Tool stiffness is utilized to determine tool deflection during the process and the results are illustrated for a range of technology parameters and tool wear. Tool deflection leads to a form deviation of the finished component as well as to changing contact conditions of the cutting edge, leading to increased tool wear. This study aims at providing a basic understanding of the relationship between milling force, tool deflection and form deviation under the influence of technology parameters and tool wear.