Materials induced vibration in ultra-precision machining

In this paper, the development of a microplasticity model for predicting the effect of crystallographic orientation on the shear angle and the chip formation, as well as on the variation of micro-cutting force are discussed. The model forms a basis for the study of material induced vibration phenomenon encountered in ultra-precision machining. Material induced vibration has its origin in the variation of micro-cutting force caused by the changing crystallography of the material substrate being cut. It is a kind of self-excited vibration which is difficult to eliminate solely by machine tool design or process control. The magnitude of such vibration inevitably affects the surface topography of the workpieces in ultra-precision machining, and this sets a limit of the performance of an ultra-precision machine. A framework of a model-based simulation system is proposed to determine quantitatively the magnitude of the vibration and its effect on the surface topography of a diamond-turned surface. Features predicted from the system are found to correlate well with experimental findings.