Study On High Efficiency Precision Cutting And Its Vibrating Characteristic

High efficiency precision cutting is one of the advanced machining technologies which possess the advantages of high efficiency and high precision. With the increase of machining speed, the influence of vibration in machining process on the efficiency, surface quality as well as the stability in machining is greatly increasing. So it becomes the important factor to limit the development and reasonable application of the high speed cutting technology. Therefore, based on the high precision turning and high speed milling, a systemically theoretical and experimental investigation on the cutting force, the dynamical characteristic of the cutting system, the vibrating and its stability, as well as the machining surface roughness and profile in high efficiency precision cutting is carried out for understanding and optimizing machining operations and upgrade their performance.The extended oblique machining theory developed with conversion of coordinates in this research is used in understanding the mechanics underlying the high efficiency precision cutting. Based on this theory, the analytical models of cutting forces for nose turning and ball-end milling were developed respectively. Taking into account the effects of cutter nose, helix angle and depth of cut, the model predicts characteristic variation of cutting forces in a series of high-speed precision machining. The changing causes of the cutting force in oblique cutting experiments are discussed using the Spectrum analyses.With the example of the super-precision and high speed machining centre, the influence of clamping force and the length of cutter(workpiece) on dynamic characteristics of different spindle/holder and cutters combination is analyzed. The dynamic characteristic of the spindle and cutter(workpiece) is compared with bare spindle's and theoretical value. It is shown that the spindle dynamic behavior can vary substantially due to effects of the structure coupling.This thesis scrutinizes the vibrations in high speed precisions machining. Considering the complexity of the structure and the force in high speed precision machining system, the experiments of idling of spindle and high speed cutting are designed and carried out to investigate thoroughly the vibration of the spindle, cutter and workpiece involved in high speed precisions machining. A solid foundation was achieved from both theoretical and experimental methods in order to analyze the vibrations involved. The changing law of the vibration of cutter/spindle in different workpiece material and different cutting parameter is discussed quantificationally.The stability of the linearized dynamic model is investigated using an analytical frequency domain method. The computation of the stability in both turning and milling are conduct to investigate the effect of machine tool dynamics and cutting parameter on the stability of the turning and ball-end milling processes. The effect of varying the clamping force and cantilever length on the stability is also investigated. Based on these observations, it is put forward that the increment of the stiffness and damping of the system is one of the basic and important ways to increase the stability of the machining system.With the help of the profiling techniques, the influences of cutting condition and vibration on surface roughness in high speed precisions cutting are analyzed systematically through a series of cutting experiments. Explanations for the observed trends are given. The tool wear form and wear mechanism in high speed precisions cutting experiments are also analyzed. The potential application of studying result in process optimization is discussed, which can be used as beneficial refer in practical high speed cutting.