Micro Machining Of Zirconia Green Body

Due to the excellent mechanical properties, ceramic materials have broad applications in micro electro mechanical system (MEMS). Using micro-cutting method to machine3dimensional structures on the ceramic green is a very promising processing method, which improves machining efficiency and reduces costs. In this paper, the edge quality, sintering shrinkage and control of dimensional accuracy were systematically investigated by milling micro-features on the zirconia green compacts.The green bodies were prepared by pressing ziconia powders in a mold with different pressures. Three-point bending tests were carried out to measure the flexure strength of green bodies. The result reveals that the strength of the bodies is a linear increase with an increase of the pressing pressure.The influence of strength of green bodies on the machining quality was investigated by machining micro structures on green bodies. The edge integrity and damage degree of microstructures were observed using an optical microscope to analyze machining quality. The observation results indicates that machining quality increases with the increase of strength of green body. The formation mechanism of removed powders attached to the cutting tool was discussed and analyzed, as well as the effect on the edge quality of cavities with straight walls and inclined walls.The ceramic compact shrinks after sintering. The shrinkages of green bodies in X, Y, Z directions were measured. The results show that under the same pressure, there is no difference of shrinkage in X and Y directions, and does not change with the height. The shrinkage in X, Y, Z directions gradually decreases with the increase of pressure, and the shrinkage in Z direction is more sensitive to pressure.In order to obtain the required accuracy of micro-features, the factors that influence the dimensional accuracy were investigated, especially the dimensional accuracy in Z direction. Firstly, the problem of setting zero position precisely before processing was solved by improving the experiment device. Then the rigidity of machining system and the axial force during machining cavities under certain machining parameters were studied to determine the compensation for the axial deformation of the system. In the other hand, the wear of tool was analyzed. The relative volume attrition rate of tool in the initial wear stage and normal wear stage was achieved and then the empirical formula was launched to calculate the axial wear of tools. Finally, by compensating the axial deformation of the system, tool wear, shrinkage, micro cavities were machined in the green body. The results show that the measured dimensions agree well with the designed dimensions after machining or sintering. The maximum absolute deviation in Z direction is1.4μm after green machining and3.8μm after sintering. It was confirmed that the compensation method can effectively control the dimension in Z direction.