Research On Miniature 5-Axis Machine Tool And Meso-Scale Milling Models

With the development of technology, especially miniaturization products in the aerospace, biomedical, defense, telecommunications and other areas become more widely used, the miniaturization technology deeply impacted in civilian and defense technology development, which have become the forefront of modern scientific research. Part size constituting of those miniaturization products which is generally a few millimeters and geometric feature size in 0.01mm~1mm belongs to meso-scale. Currently the main technologies used for manufacturing meso-scale are the MEMS and ultra-precision machining technology. Meso-scale milling as a way to overcome the MEMS technology many technical limitations including of difficultly machining complex three-dimensional shape, relatively low processing accuracy and materials limitations, etc. It have become a very active research focus because of its high flexibility, high efficiency, the processing capacity of complex shapes and the characteristics of a variety of materials. For machining the complex three-dimensional miniaturization parts, corresponding need to develop a miniaturization 5-axis machine tools. On this basis, to carry out the meso-scale milling process models is designed to optimize the processing of miniaturization parts, and improving parts quality.This paper introduced the meso-scale milling maturing technology research status. Listed researches of miniaturization machine tools, then focused on researches of the cutting chip formation and the minimum thickness, and deeply introduced the researches of milling force, milling surface topography, tool wear monitoring, etc.For machining the complex three-dimensional miniaturization parts, a self developed 5-axis micro-milling machine tool was developed. This paper firstly introduced hardware and software structure of the machine system. Based on C++ language, the control system which had friendly HMI (human machine interface) and can perform high-capacity CNC code was developed, and then interpolation error of the CNC system was analysed. Achieved thin-wall structure, curve thin wall fabric and mini impeller processing tests by using the strategies which were suitable for meso-scale milling, then the processing capacity of 5-axis milling machine was verified.The diameters of micro-milling tools are between 0.1mm~1mm. If the cutting parameter is unreasonable, it can make the cutting force exceed a certain value to result of tool in an instant broken. For this, this paper used micro-ball-end milling tool as the example to establish a meso-scale milling force model. Based on analysis of cutting edge geometric characteristics of micro-diameter ball milling, the cutting edge trajectory model was established, and accordingly concluded that the single edge cutting phenomenon may occurred in meso-scale milling, given the single edge cutting phenomenon criterion and the effect factors at the same time. Established the actual instantaneous cutting thickness model based on researches of chip formation. Extracted cutting element based on solid modeling, and proposed a new tool runout parameters identification algorithm. Then actual cutting force measurements were given to verify the accuracy of the model.The part surface topography will affect the reliability and life of machinery or equipment. In order to study the various effect factors of the meso-scale milled surface topography, the paper established the milling surface topography model based on taking into account the machine-tool system dynamic characteristics. It used Receptance Coupling methodology learning from the structures engineering to obtain the displacement frequency response of machine-tool system firstly. Combined of cutting force model to calculate the dynamic deflection of the tool, and then introduced to the tool path equations. Finally, a dynamic milled surface topography model was established. Some influencing factors of the surface topography was analyzed combined with measuring surface roughness by confocal microscope, and thus validated the validity of model algorithm.Micro-milling tools because of their small diameter, high speed, tool wear has restricted the development of micro-milling technology as an important factor. The Hidden Markov model (HMM) was introduced into micro-milling tool wear condition monitoring, and a monitoring model was established. Firstly, whether the single edge cutting phenomenon was judged, and respectively measured cutting force of single edge cutting and two edges alternate cutting, and extracted cutting force feature to train the HMMs of two cutting phenomenon. Using multiple cutting parameters repeated above process, established the three tool wear states HMMs, respectively. The actual tool wear monitoring results demonstrated the feasibility of the model which provided the basis for further research of meso-scale milling process.