Investigation of variable spindle speed face milling for tool-work structures with complex dynamics: part 2 - physical explanation

Part 2 of this paper focuses on the explanation, both on theoretical grounds and through model simulations, of why the technique of variable spindle speed machining is an effective tool for increasing the quality and productivity of machining operations. In particular, Part 2 explains why, by disturbing the regenerative and forced vibration excitation frequencies which generate large amplitudes of vibration during constant speed machining, variable speed machining has the potential to reduce the vibration of the tool-work system and be robust with respect to the cutting process dynamics. The explanation is based on the work done by the cutting forces, the chip load variation, tool-work displacements, cutting forces, and workpiece surface error generated by both constant and variable speed machining. By investigating the effects of regeneration and forced vibration during variable speed machining on the vibration of tool-work systems having thin widths of cut and different cutter diameter-to-workpiece width ratios, it has been shown that variable speed machining is also robust with respect to the geometry of the tool-work system. This work concludes that variable speed machining is safer to use than constant speed machining when the effects of the tool-work dynamics and geometry on the vibration of the cutting process are hard to determine.