Time Domain Analysis Of Flutter Stability Of Milling System With Variable Pitch Milling

As one of the main processing methods,milling is becoming more and more widely used in metal manufacturing.The flutter phenomenon in the milling process is the main dynamic unstable phenomenon in the milling process,which seriously affects the stability of cutting,hindering the high-efficiency and high-precision machining.It is very important to study the vibration control in the milling process and improve the machining of the machine tool.As a better control method of flutter stability,variable pitch milling can optimize machining parameters and tool structure,and achieve maximum removal rate of flutter-free material in machining process,and it has a certain research value.In this paper,the flutter in milling is taken as the research object.Based on the previous research results,the dynamic analysis and stability limit prediction of the machining process are mainly as follows:1.This paper introduces the flutter effect of milling process and milling process,establishes the geometric model and dynamic model of the flutter of the milling system of equal pitch milling cutter,and on this basis establishes the geometric model and the dynamic model of the variable pitch milling cutter system.2.The Floquet stability criterion is expounded.Then,the finite element method(TFEA)with Hermite cubic interpolation is introduced to solve the differential equations of time-delay motion in variable pitch milling system.The stability of the system is evaluated by the stability criterion and limit prediction of the milling system.The influence of these factors on the stability of the system is analyzed by considering the variation pattern,the number of teeth and the helix angle of the tool.The time-domain simulation method is used to obtain the cutting force and the time-domain diagram of vibration displacement for the working point under certain working conditions.According to the simulation results,the stability of the milling system under this condition is judged and compared with the stability determined by the time-finite element method to verify the accuracy of the time-based finite element method in predicting the stability of the system.In addition,the principle and steps of the zero-order approximation frequency-domain method to draw the stability of the leaf system of the milling system are discussed,and the image is compared with the image made by the time-finite element method.3.The influence of process damping is further considered.A dynamic milling model based on process damping is established,and the stability limit prediction and analysis are carried out.The effect of modal parameters and process damping coefficient on milling stability is considered.It is found that under the condition of low speed rotation,there is a clear upward trend in the process of damping,which is higher than that in the process of damping without considering process damping.With the increase of speed,the influence of damping becomes smaller and smaller,that is,process damping has more influence on low speed operation.