Investigation of the Effects of Process Damping on Chatter Instability in Micro End Milling

In this paper, chatter instability of micro end mill tools is studied by taking into account the process damping effect. The actual geometry of the micro tool including shank, taper part and fluted section is considered in the analysis. Timoshenko beam theory is utilized to consider the shear deformation and rotary inertia effects due to short and thick beam-type structures of each parts of the micro tool. The extended Hamilton's Principle is used to formulate a detailed dynamical model of the rotating micro end mill. The governing equations are solved by assumed mode model expansion. An exact dynamic stiffness method is developed to investigate modal characteristics of the tool including mode shapes to be utilized as base functions for the solution. In micro milling, the process damping affects the chatter especially at low spindle speeds. So, the process damping parameters are used to investigate chatter instability.