Model-based analysis in finish broaching of inconel 718

Abstract

Broaching is still state of the art for manufacturing profiled slots in turbine discs. The broaching processes can be divided into roughing, semi-finishing, and finishing. The functionality of the manufactured slot is mainly determined by the finishing process with regard to the groove geometry and the surface integrity. Since the broaching tool is in contact with the entire fir tree slot in the finishing process, the highest process forces are expected in finishing and semi-finishing. In case of dedicate geometries, the high process forces can lead to the deformation of work piece material, and thus to geometrical inaccuracies. The process and tool design in turbine discs broaching processes are based mainly on experiences. Therefore, the new process and tool design are time- and cost-consuming by means of experiences-based design, for example, by implementation of new cutting material, such as carbide broaching tool. To predict the process forces in dependence on the slot geometry in broaching process, an analytical force model and a FEM model with coupled Eulerian-Lagrangian(CEL) formulation are introduced in this work. The investigated parameter range is based on the typical range for broaching with high speed steel for vc = 2.5 to 5 m/min, rise per tooth h = 0.02 mm. By means of the new model based approach, the broaching process and tools can be designed and optimized on the model level.