Theoretical and experimental investigation of the tool indentation effect in ultra-precision tool- servo-based diamond cutting of optical microstructured surfaces.

Ultra-precision tool-servo-based diamond cutting (UTSDC) is a promising technology for fabricating true 3-dimensional optical microstructures. The diamond tool in UTSDC moves alternatively upward and downward along the thrust direction. However, most studies on the material removal mechanism are limited to the orthogonal cutting condition where the depth of cut is invariant. The effect caused by the tool motion in the thrust direction has been overlooked. In this paper, the indentation effect affected by the tool path, tool shape and cutting speed is systematically studied. It is found that the inclined angle between the tool path direction and the main cutting direction plays a key role in the determination of the material spring back and the formation of side burr. The characteristics of indentation force and material spring back indicates that the indentation mechanism is dominant in the cut-in process where the inclined angle is large, while the shearing mechanism is dominant in the cut-out process. A new theory is proposed to explain the tool indentation mechanism in UTSDC, and the simulation results show that the theory can well predict the indentation force under various cutting conditions.