Mechanical Lapping And Measurement Techniques Of Nose Arc Of Rounded Diamond Cutting Tools

As the representative technology of ultra-precision machining, the ultra-precision cutting becomes an important mark of the manufacturing level of a country. The ultra-precision cutting needs not only cutting machine, high accurate detecting instruments and ultra-stable machining environment, but also high-precision rounded diamond cutting tools. In America and Japan, the cutting edge radius (sharpness) of the tools is minimized less than 10nm and the nose roundness of the tools is improved no more than 50nm. Compared to the cutting edge radius of the tools, domestic has approached the international advanced level, but the nose roundness is left behind a great distance with that. Therefore, it is urgent to solve the high-precision lapping problem of rounded diamond cutting tools'nose arc.The diamond crystal has strongly anisotropy. Mechanical properties in different crystal planes even in different orientations of the same plane are obviously different. Each part of the tool's nose arc has different lapping performance as they are in different crystal planes. Thus, the simple cylindrical lapping method is not efficient to lap the nose arc of rounded tools. So far there is no effective model for the lapping of the nose arc. And the existing lapping equipments and process has many drawbacks. Therefore, the nose roundness of the lapped nose arc cannot reach the high precision. With the result that, this paper develops the lapping mechanism, equipment and detecting technology of the tool's nose arc based on crystallology. The research contents are detailed as following:Firstly, the microscopic mechanism of material removal in mechanical lapping of diamond cutting tools is discussed using the period bond chain (PBC) theory and molecular dynamics simulation. It is the first time that this microscopic interpretation for mechanical lapping of diamond cutting tools exposed on atomic scale from the crystallography. And the theoretic basis is established for mechanical lapping of nose arc of the tools by this interpretation. According to this interpretation, a PBC model is built to evaluate the extent of hard lapping in different orientations on different crystal planes in diamond. This model is confirmed by the subsequent experiments of material removal rate in mechanical lapping.Secondly, based on the PBC model, ratio models of material removal rate are proposed for nose arc of tools which use the {100} and {110} crystal plane as the rake faces. The materials lapping performance on nose arc is described by mathematical model for the first time. Further more, these models will give strong support to effective mechanical lapping of the rounded diamond cutting tools'nose arc. And then, the optimization lapping direction is obtained for the nose arc of tools with different rake face. And the optimization composition of the crystal plane is R(110)F(110) for the rounded tools. More over, two lapping methods are proposed for nose arc according to the formula of material removal amount. One is varying lapping pressure; the other is varying lapping time.Thirdly, summarizing of the disadvantages of the existing lapping machine, a new type lapping machine is designed by top-down method of Pro/Engineering for mechanical lapping of rounded diamond cutting tools. This lapping machine uses T-type layout in order to eliminate the coupling error introduced by the overlapping layout of mainshaft (C-axis) and pendulum shaft (X-axis). Oscillating shaft is controlled by the position and speed closed-loop. This ensures the varying lapping pressure and varying lapping time two kinds of lapping methods feasible. In addition, the space error model of the lapping machine is established by means of lower body array to describe the topological structures. And the principal factors are obtained for influencing the lapping quality of rounded diamond cutting tools'nose arc.Re-lapping of the worn diamond cutting tool is an urgent problem to be solved. This paper discussed the key technology and implementation method of tools're-lapping based on the analysis of key difficulty. Whereafter, a whole process plan is set down for re-lapping of rounded diamond cutting tools'nose arc.The measuring apparatus is necessary to evaluate the lapping quality of the diamond cutting tool. As yet no measuring method is applicable for the nose roundness of the rounded diamond cutting tool. Lastly, this paper put forward a measuring method based on atomic force microscope (AFM) according to the requirements of the diamond cutting tool. A measurement apparatus which composes of a reconstructed AFM and a precision aerostatic bearing is developed. Thereafter the error source and composition of the whole system is analyzed, especially the error caused by alignment. And the measuring accuracy of the measuring system is worked out. Then a new data processing method with radius constraint least-square circle fitting is put forward. This new method will give a strong support to the measurement and evaluation of the nose roundness of rounded diamond cutting tools in engineering practice.