Milling Force Modeling And Tool Life Prediction In Micro-Milling

The micro-milling is the micro-machining technology that uses micro-cutters to remove small amounts of workpieces on precision and ultra-precision machine tools,with which micro-scale structures or parts are achieved.It combines the characteristics of computerized numerical control(CNC)machining and micro electro mechanical system(MEMS)technology.The machining feature size of the workpiece is usually between 1 micron and 1 millimeter.It is widely used in aerospace and electronic communications.Micro-milling has the characteristics and technical advantages of strong adaptability of processing materials and structures,high efficiency,low cost,and it has become an effective way to realize three-dimensional complex surface processing.Compared with the conventional milling method,the researches on micro-milling still meet some key problems that need to be solved urgently,such as the size effect of the micro-cutting edge,multi-flute intermittent cutting at ultra-high rotational speed,and rapid tool wear,etc.Tool wear is one of the main factors affecting the machining accuracy and efficiency of workpieces.Based on the cutting mechanism and tool wear mechanism of the micro-milling process,the paper completes the accurate modeling and application of the generic micro-milling force model,the identification of milling state,the analysis of tool wear and the prediction of tool life,etc.Considering the size effect and tool runout effect,generic models of micro-milling force and tool wear are established,respectively,which provide a theoretical and practical foundation for improving the service life of the tool and the machining accuracy and production efficiency of parts.The main research contents and innovations of the paper are as follows:(a)Instantaneous undeformed chip thickness model in micro-millingThe modeling of the micro-milling force is an important foundation for recognizing the milling mechanism and dynamic process.The instantaneous change of the milling force can not only indirectly reflect the cutting chatter,tool deformation,wear and energy loss,etc.,but also an important basis for the study of milling technology and automation.This paper focuses on the shortcomings of the current research and the contents that need to be studied urgently,and introduces the establishment of a more accurate model of micro-milling instantaneous undeformed chip thickness,by comprehensively considering the cutting edge trochoidal trajectory,size effect and tool runout and other influencing factors in the machining process.On this basis,the contact state between the cutting edge and the workpiece is analyzed,and the determination method of milling force coefficients in the micro-milling force model is clarified.In addition,based on the milling force signals and vibration signals collected experimentally,the tool runout in micro-milling is estimated online in real time.(b)Theoretical model of micro-milling force per tooth and identification of milling stateBased on the instantaneous undeformed chip thickness model considering tool runout and size effect,the paper conducts an in-depth analysis of the established three-dimensional dynamic micro-milling force model for each tooth,and an extended model is proposed.Based on the model,the instantaneous milling state of the tool during machining is identified.A generic micro-milling force model is established by analyzing the trochoidal trajectory of the milling cutter.The effect of the milling state of the tool on the thickness of the undeformed chip,and the calculation error in the process are analyzed.Finally,the validity of the generic per-tooth micro-milling force model is verified experimentally.(c)Generic tool wear modelCombined with the experimental sampling data,a generic model of tool wear is established,the influence of wear model parameters on the tool wear value is clarified,and a theoretical basis for selecting appropriate machining conditions is provided.Flank wear experiments of various workpiece materials and milling conditions are designed and completed,and the wear coefficients of the established tool wear model are optimized through the wear data of multiple samples.Considering the influence of tool wear in micro-milling,the generic force model per tooth is further improved.(d)Tool life prediction theoryBased on the analysis of the tool wear conditions,the method for determining the wear coefficients in the proposed tool wear model is clarified.On this basis,the mechanism relationship between tool wear and tool life is analyzed,and a tool life prediction model is proposed.With the real-time tool wear data samples,the tool life is predicted,and the time deviation is verified by experiments to further improve the wear model.Finally,based on the aforementioned research,a micro-milling process visualization analysis software is established,which includes functions such as solving the milling force of micro-milling,predicting tool wear and tool life,etc.