Modified bull-nosed milling stability analysis with the usage of pre-estimated cutting force coefficient fitting curves

The milling processes are widely used to increase the flexibility of production operations. A lot of research of the cutting conditions enhancement have been carried out. One of the main purposes of such investigations is determining and increasing the tool vibration stability limit. The usage of intense cutting conditions for rough and semifinish machining is limited, to a greater extent, by the possible occurrence of dynamic instability of the system, i.e. the occurrence of self-excited vibration or chatter of one or more system components. The main objective of the paper is to define stable cutting conditions by means of stability analysis method. The applicability of the two degrees of freedom zeroth approximation model is estimated in the case of bull-nosed end milling of a part with negligibly low flexibility compared to the holder-tool assembly. The algorithm of holder-tool frequency response function of holder-tool thermal shrink fit joint is determined by the finite element modeling with elastoplastic properties of end mill and tool holder materials. The experiment was carried out on S500L milling machine tool on titanium alloy with bull-nosed carbide end mill. The main vibration measuring components of the system are two eddy current displacement sensors. For verification, several machining experiments are carried out and the comparison between the results of analytical modeling and tests is made in terms of stability lobe diagram.