Research On Vibration Stability Of Five-axis Wide Strip Machining Of Freeform Surface

Metal parts with curved surface structure are widely used in aerospace,automotive and energy.At present,the main processing and forming method of this type of parts is five-axis CNC milling,and the flat-end mill is one of the most commonly used cutters.The milling force is an important physical parameter for studying the machining process,and it is also the basis for optimizing the process parameters and studying the machining vibration.Especially for five-axis curved surface machining,due to the limitation of the surface shape of the part,the tool needs to ensure the corresponding overhang to avoid interference.This makes the tool system less rigid than the workpiece system,and prone to chatter during processing,which affects the processing quality and processing efficiency.Therefore,it is of great theoretical significance to study the milling force and dynamics of curved surface five-axis machining for optimizing the machining process and improving the machining quality and efficiency.In this paper,for the five-axis machining of curved surfaces,based on the discrete idea,the cutter contact geometry is analyzed,and the milling force model for curved surface machining is established.A simple cutting experiment was used to obtain the modal parameters of the machining system,and the milling stability prediction of the five-axis machining of the curved surface was realized.The main research contents are as follows:(1)Based on the idea of differential discrete,the continuous curved surface five-axis machining is approximated to a series of oblique plane five-axis machining along the tool path.Taking the oblique plane five-axis machining as the research object,the contact geometry of the tool and the workpiece in the machining state is analyzed based on the analytical method,and a semi-closed space containing the cutter workpiece engagement(CWE)is constructed by the characteristic geometric surface of the cutter contact system.It is used to judge whether the cutting edge element participates in the cutting.According to this condition,the in-cut cutting edge(ICCE)can be obtained along the cutter edge curve directly.Finally,by comparing with the simulation results obtained by the solid modeling method,the correctness and effectiveness of the proposed space limitation method are verified.(2)Based on the idea of differential discrete,the oblique plane machining is used as the basic unit of curved surface machining.For the oblique plane five-axis machining,the calculation formula of the undeformed cutting thickness is derived.Combined with the ICCE,a milling force prediction model is established based on the mechanical model.The cutting force coefficient can be identified by the cutting experiment,and express the coefficient as a function related to the uncut thickness.By analyzing the spatial coordinate conversion relationship between the discrete inclined plane and the curved surface,the five-axis milling force model of the inclined plane can be applied to the prediction of the milling force of the five-axis machining of the curved surface based on the idea of differential dispersion.(3)For the weakly rigid cutter system,the modal parameters o f the tool system are back calculated by using the zero order method and the simple cutting experiments.And further through the experiment to complete the optimization of the selection of modal parameters,to achieve the identification of the modal parameters of the tool system in the working state.It is compared with the modal parameters obtained by the hammer test.Combining the identified modal parameters with the dynamic model,the zero order method is used to calculate the critical cutting depth,so as to predict the stability of the five-axis surface machining.