The Study On The Methods Of Fabricating A Large Aperture Flat

As an important technology of fabricating the flats, the annular polishing is applied widely all the time. In our laboratory it is used to fabricate a rectangle flat with high precision, high aspect ratio and large aperture. In order to understand the theory of the material removal and control the polishing, the annular polishing was analyzed theoretically and proved by the experiments.In order to analyze the material removal, a material removal model was build, based on the relative motion between the work piece and the polishing lap and the Preston hypothesis. Based on the theoretical model, the pressure and the relative velocity between the work piece and the polishing lap were analyzed respectively. The pressure distribution between them was gotten on the basis of the theoretical analysis. Besides, the rotating ratio and the eccentric distance were also analyzed to control their effect on the polishing. Then the correct plate was studied because it is an important component of the annular polishing. During the polishing, the correct plate played an important role in improving the flatness of the lap and was helpful to heighten the surface precision by changing its position on the lap.The experiments were carried out on the basis of the theoretical analysis. The theory on the material removal was proved by controlling the factors. Then, the surface errors of the rectangle flat were analyzed and some methods were given to solve these problems.Based on the theoretical analysis and the experiments, it is feasible to fabricate a rectangle flat whose aperture beyond the annular width, which was helpful to guide to fabricate the large flats.