Vibration Analysis And Deformation Prediction For Milling Thin-walled Parts

With the development of the manufacturing industry, the traditional processing methods have been difficult to meet the needs of the industry. High speed machining technology arises at the historic moment. In order to improve the cutting speed and machining efficiency and quality and reduce processing costs, high speed machining technology adopts super-hard material tools and abrasives, which uses high precision, high automation and high flexibility of manufacturing equipment. It has been widely used in aviation and aerospace. However, the use of lightweight aluminum alloy thin-walled parts in aerospace products, in high speed machining, the phenomenon of vibration is very easy to occur, which leads to the increase of the deformation of the workpiece and not meet the processing requirements. Therefore, It is necessary to predict the machining deformation of the workpiece based on machining process parameters, which can improve the machining quality and yield.However, there are some difficulties to realize the prediction of machining deformation of aluminum alloy thin wall parts:(1) Construction of dynamic milling force model based on cutting parameters; (2) Construction of dynamic model and prediction of dynamic behavior of machining system by the effects of dynamic cutting force; (3)Construction of prediction model of machining deformation of thin wall parts by the effects of dynamic cutting force; In order to solve these problems, in this paper, the typical thin-walled part of cantilever plate structure is studied, the modal analysis, milling force modeling, dynamic modeling and vibration characteristic analysis and prediction modeling of machining deformation of thin wall parts are studied. It mainly contains the following contents:(1) By analyzing the thin wall parts processing technology system, the stiffness of the machine tool is higher than the workpiece and tool, so the machining process is simplified to the workpiece subsystem and the tool subsystem. The modal analysis of the workpiece subsystem and the tool subsystem is carried out to obtain the most prominent plane of the vibration of the machining process system and modal mass, modal damping and modal stiffness, it is the foundation of the construction of dynamic model of thin wall parts processing system(2) A dynamic cutting force modeling method is proposed, firstly, cutting process of cutting edge is divided into stage of cut in, stable and cut off, The micro cutting force model were built in different stages of the cutting edge. Then, by analyzing the length of single tooth cutting edge, integrating all the micro cutting forces in the length and calculating the number of tooth at an instant, a dynamic cutting force model is established for the whole cutting tool. A milling force model based on dynamic displacement is established through the relationship between milling force and vibration displacement of tool and workpiece. last, the correctness of the method is verified by experiments.(3) By analyzing the relationship between milling force and vibration of the machining process system, dynamic model of the machining process system of thin-walled wall is built on the basis of milling force and modal analysis. It is used to analyse the dynamic characteristics of the machining system. Based on this model, a prediction method of chatter stability in milling process of thin-walled parts is presented, which is used to judge the stability of the machining process with different cutting parameters, last, the correctness of the model and method is validated by experiment.(4) Based on the prediction of method dynamic milling force model and flutter stability, the finite element model of machining deformation of thin-walled parts is established, which can realize the prediction of deformation of thin wall parts before machining. It provides support for optimization of machining process parameters for thin wall parts. Last, the correctness of the model is verified by experiments. The effect of vibration a on machining deformation is analysed by experiment.Through the research of the above four aspects of machining process of thin walled parts, a systematic approach to predict the deformation of thin-walled parts is established. It provides meaningful methods and conclusion which improve the productivity of thin-walled parts processing and percent of pass, and optimize process parameters.