| With the rapid development of science and technology,micro parts and structures have wider application in high-technology medical devices,precision machinery and other fields.Micro-milling technology is one of the most important technologies of processing micro parts and structures.It machines wide kinds of workpieces with high precision and relatively high processing efficiency,which meets the processing requirements of micro parts and structures.However,chatter phenomena occur during micro-milling,which can obviously reduce machining accuracy,machining efficiency and machine life.Therefore,the premise of achieving high precision micro milling is the acquisition of chatter stability lobes,for which the premise is fast acquisition of accurate tool point frequency response function(FRF).On one hand,it is impossible to hammer on the tip of the micro milling tool,on the other hand,most of the present stability lobes are gained under static condition,while the dynamic characteristics of machine tools when the spindle is stationary are different with those at high rotating speed.Thus,it is necessary to explore new ways to research on predicting stability of micro-milling quickly and accurately considering the centrifugal force and gyroscopic effect caused by highpeed rotation of spindle.The author considers the centrifugal force and gyroscopic effect caused by high-speed rotation of spindle,realizes the rapid prediction of FRF of micro-milling tool point with theoretical method,and finally obtains the micro-milling stability lobes which used for the optimization of cutting parameters.The results lay foundation for high precision micromilling of micro parts and structures.The main contents of this pape are as follows:The FRF of each stepped shaft is solved by using the theory of rotating Timoshenko beam theory after simplifying the spindle system into a number of stepped shafts.Then the FRF of the spindle is obtained using receptance coupling substructure analysis when the bearing properties are added by means of structural modification and the connection parameters between spindle and tool are solved by genetic algorithm.Finally,the FRF of micro-milling tool point considering centrifugal force and gyroscopic effect is obtained.Modal parameters are identified and transformed into physical parameters.Based on the fast solving method of the tool point FRF proposed in this paper,the FRFs of tool point of different spindle speeds,bearing properties,connection properties and tool extended length are quickly solved to discuss the effects of spindle speed,bearing properties,connection properties and tool extended length on the FRF tool point.Based on the equivalent physical parameters solved by the tool point FRF and the micromilling force model established earlier,the micro-milling process is simulated and the micro-milling stability lobes are achieved.Finally,the micro-milling experiments are conducted to verify the accuracy of the micro-milling stability lobes. |
