Research On Theory Of Milling Stability Analysis In Time Domain

As one of the main means of manufacturing, milling has been widely used in manufacture of metals. Chatter is one of the most important dynamic instability phenomena in the cutting process, which will seriously affect the machining quality and productivity, and cause wear and damage of the tool, and also reduce the service life of machine tools and cutting tools. Vibration control in milling process has important application value, which is currently one of the frontier research topics in the field of mechanical design and manufacturing.This paper deals with the dynamic analysis and stability prediction of the milling process. The main research content and achievements are as follows:(1) Considering the regeneration effect in the milling process, the two DOF milling dynamics model is established and the method of milling chatter stability analysis in the time domain is put forward. The tooth pass period is divided into multiple elements, and three times interpolation polynomials are structured in each element, then the response of the system vibration is represented approximately as a linear combination of the motion state of discrete time points on a single element. The weighted residual method is used to build the Floquet state transfer matrix of the system, and the corresponding stability criterion is put forward based on the Floquet theory.(2) The stability limit of a 2-DOF milling system is forecasted based on dynamic milling model and stability analysis theory in time domain. And then, the result is verified by time domain simulation and bifurcation analysis. In addition, this paper studies the stability of milling process simultaneously engaged cutting teeth, and analyze the influence of radial immersion and the number of cutter teeth on the stability limit:along with the increase of the radial immersion and the number of cutter teeth, more teeth will simultaneously engaged in cutting, and the continuity of the milling process will be enhanced, but the stability limit will decrease gradually, and the stable cutting parameter domain will become smaller and gradually move towards the low speed region.(3) This paper also considers the effect of helical angle, and establishes the dynamic milling model based on helical angle, and the stability limit of helical milling process is predicted. It is found that the stability lobes figure has obvious Flip bifurcation phenomenon and closed curve which is called unstable island due to the existence of helical angle under the condition of low radial immersion. With the increase of the radial immersion, number of teeth and helical angle, the closed unstable island and Flip bifurcation phenomenon will gradually disappear.(4) The influencing factors of the accuracy of the algorithm based on the theory of the stability analysis in time domain are analyzed. It is confirmed that different weighting function has no effect on the calculation results, and improving interpolation numbers has little impact on calculation accuracy, but will increase the amount of computation. Increasing the number of temporal elements is helpful to improve the calculation precision, but also increase the amount of calculation.The work on dynamics analysis and prediction of milling stability in this paper is helpful and useful to the parameters optimization of machining process, machining of high efficiency and the enhancement of the level of milling process.