Modelling of Process Forces in Broaching Inconel 718

Broaching is the standard machining process for fir-tree slots in turbine discs. Due to the fact that Inconel 718 turbine discs belong to the safety critical components of aero engines, there are high demands on dimensional accuracy and surface quality. The cutting parameters as well as tool, fixture and machine tool are critical factors to fulfill these high requirements. Within the next years the process has to be designed for the needs of new turbine disc geometries, disc materials and tool materials. Therefore, detailed knowledge about process forces is an essential prerequisite. Modern 2D FEM simulations enable calculations of the thermo- mechanical load collective in the chip-tool interface.A 2D chip formation model of the broaching process has been designed to calculate cutting forces for process relevant parameters, as the rake angle, rise per tooth and cutting speed. Depending on these parameters a multivariate regression model has been de- veloped. The chip formation and the multivariate regression model have been validated on a test bench for fundamental cutting investigations, simultaneous process forces were measured and high speed films were recorded. This paper thoroughly discusses the results and evaluates the application potential.