Research Of Accuracy Characterization And Quality Control In The Area Of Micro Milling Considering Scale Effect

In recent years,with the miniaturization tend of mechanical products,workpiece in the meso scale has been used widely in many fields,such as medicine,aerospace,military and other high-tech electronic products.In the field of mechanical machining,the meso scale machining refers to the field of workpiece size in 0.1~10mm,or the feature size in 0.01~1mm.Because of the extremely small amount of cutting in the processing of this scale,the serious scale effects will occur,also many of the features are different from the processing in the conventional scale.Just due to this,the micro cutting technology arises,and attracts more and more scholars' attention.As one of the most important parts,micro milling technology has also become a hot research area.As the existence of scale effect,many new problems have been produced in the process of micro milling in the meso scale.In the evaluation of surface quality,for the small feature size of the workpiece can not meet the requirements of the sampling length in the conventional characterization methods,the evaluation results is often difficult to accurately represent the actual processing surface;in a single procedure,for the small size of workpiece and cutter,leading to weak stiffness,the deformation which is not significant in conventional processing increases rapidly,and severely influences the machining precision of the workpiece;in the whole process,for the small scale and the complex geometric feature on the workpiece,often needing more procedures than that in the conventional scale,the difficulty of the precision control of the workpiece in the field also increases.In order to solve the problems above,in this paper,the theory of fractal geometry,the principle of flexure deformation superposition and the model of error stream transfer were introduced into the field of micro milling,and the workpiece quality in this field is studied,main research contents include the following aspects:(1)Based on the fractal geometry theory,a surface quality characterization method used fractal dimension as the evaluation index was proposed,which couldget rid of the limitation of the sampling length and the evaluation length in the process of mesoscopic scale,also the changing trends of the surface quality with the cutting elements under this method was given.(2)Based on layered superposition principle about the deformation of cantilever beam structure with weak stiffness under load,according to the cutting force prediction model in the micro milling process,by means of mathematical method,the prediction and corresponding compensation method of deformation error in this machining process were obtained.(3)Based on the error transfer model of machining process with multi-procedures,aiming at the key characteristics on the workpiece of mesoscopic scale,by using the method of matrix operation,the error transfer law of this process was explored,and the prediction expression was obtained.(4)Selecting the materials difficult to machining,austenitic heat resistant stainless steel 06Cr25Ni20,various forms of micro milling experiments were carried out to verify the applicability and accuracy of the theory of fractal geometry,the superposition principle of flexure deformation and the model of error stream transfer in the machining process mesoscopic scale,and provided experimental support for the realization of the quality improvement in micro milling machining process.