Study On Electronic Characteristics Between Probe And Workpiece In Micro Nano Machining

With the continuous development of modern industrial technology, industrial products and household items become miniaturization and precision. Technology of Micro-EDM, as a non-contact processing technology, is widely used in many fields, such as aerospace, microelectronics industry,medical equipment, mould manufacturing and so on, by virtue of the characteristics of high-precision and regardless of material properties. And now it has become an important part of micro-processing field.However, with the requirements of precision machining become more miniaturization. It is difficult for us to observing phenomenon by experiment because of the small discharge gap and immersed in the working fluid. This make the research of micro-EDM mechanism slow. On the other hand, computer simulation technique based on similar principle and model analysis has been widely used in precision machining technology as a powerful means.In previous studies, people done little research on the role of elements play between electrode and workpiece. Therefore, we use the method of first principle in density functional theory(DFT) and non-equilibrium Green’s function to study the transmission characteristics between different electrodes and the elements of carbon, iron and chromium in the workpiece. The main content of this paper is the following aspects:In chapter I, we mainly introduced the development, principles, characteristics, classification, materical of commonly used electorode of micro-EDM technology and what we do in this paper.In chapter II, we described the basic calculation methods and theoretical knowledge used in this paper in detail, including first principles calculation method, Density Function Theory and green function. At the end of this chapter, ATK, software used in this paper, is introduced.In chapter III, according to the method of first principle that based on density function theory(DFT), ATK is used to built the basic model of workpiece with carbon element, and calculate the transmission spectra, density of state, energy gap and total energy of the three different systems that are plane-as well as three-dimension of tungsten electrodes and plane-dimension of nickel electrode; with different distance,the change of transmission characteristics of the system that plus plane-dimension of tungsten electrode is also calculated. The results show that the density of states of all the transmission systems are continuously distributed, this indicates that the transfer process are quantized transmission; we also can find that the peak of transmission spectra and density of state is corresponding each other and energy with wide band is existed and have a strong polarizability; The ability of electron transfer with three-dimension of tungsten electrode is stronger than the other two kinds; As a prscessing electrode, nickel electrode is better than tungsten electrode, three-dimension electrode is also better than plane-dimension electrode; the eigen level and electronic tunneling decrease as with the increase of the distance, and the electronic transmission probability is reduced. The process of the electro discharge machining stops since the electrons can not transport when the distance between the electrode and workpiece is greater than0.4nm.In chapter IV, according to the method of first principle that based on density function theory(DFT), ATK is used to built the basic model of workpiece with iron element, and calculate the transmission spectra, density of state, energy gap and total energy of the four different systems that are plane-as well as three-dimension of tungsten electrodes and plane-dimension as well as three-dimension of nickel electrode; with different distance, the change of transmission characteristics of the system that plus plane-as well as three-dimension of tungsten electrode is also calculated. The results show that the ability of electron transfer and effect of machining of three-dimension electrode is better than that of plane-dimension electrode. In addition, electron transport of the systems that plus plane-dimension electrode of tungsten is stoped, when the distance between electrode and workpiece is greater than0.48nm. And when the distance between electrode and workpiece is greater than0.58nm, this situation appears in the system that plus three-dimension electrode of tungsten.In chapter V, according to the method of first principle that based on density function theory(DFT), ATK is used to built the basic model of workpiece with chromium element, and calculate the transmission spectra, density of state, energy gap and total energy of the three different systems that are plane-as well as three-dimension of tungsten electrodes and three-dimension of nickel electrode; with different distance,the change of transmission characteristics of the system that plus plane-dimension of tungsten electrode is also calculated. The results show that the ability of electron transfer and effect of machining of three-dimension electrode is better than that of plane-dimension electrode; Electron transport of the systems that plus plane-dimension electrode of tungsten is stoped, when the distance between electrode and workpiece is greater than0.41nm.In chapter VI, we summarize the contents that have been done in this paper and raise a prospect for future research.