Research On Control Methods Of Surface Quality Of KDP Crystal In Ultra-Precision Machining

The KDP (Potassium Dihydrogen Phosphate) crystal is widely used in the non-linear optical areas as a high quality non-linear optical materia1. But the KDP crystal is recognized as the most difficult machined optical material because of the surface mechanical properties, and the KDP crystal ultra-precision technique is kept secret in other countries. Therefore the level in the aspect of the advanced ultra-precision optical fabrication technology must be raised as soon as possible, and the KDP crystal machining mechanism and processing technology must be studied in further in order to meet the demands of high quality machined surface using in the optical field.The methods of raising the surface quality of the KDP crystals ultra-precision machining are mainly studied in this paper.Firstly, the experiment is designed by general rotation design of regression method, and the experimental dates are analyzed using regression analysis method, then the prediction models of surface roughness in different crystal planes corresponding to the cutting parameters are acquired. The influence law of cutting parameters on surface roughness can be obtained by analyzing the prediction models.Secondly, the finite element model for ultra-precision cutting process of the KDP crystal is built successfully according to the material properties of KDP crystal, and the cutting process is simulated using the commercial software Marc in this paper. The effect of the cutting parameters on chip geometry shape, equivalent stress and equivalent strain is analyzed by the finite element simulation. At the same time, the finite element simulation data are analyzed using regression analysis method, and the prediction models of equivalent stresses and strains corresponding to the tool geometrical parameters can be obtained. The influence law of tool geometrical parameters on equivalent stress and equivalent strain can be acquired by analyzing the prediction models.Finally, a group of optimized cutting parameters are obtained by optimization of prediction models using MATLAB, which makes the surface quality achieve the best, and on this basis a visual user interface is programmed to achieve parameters designing of KDP crystals ultra-precision machining. Thus it is available to better forecast and control machining surface quality before ultra-precision machining of the KDP crystals.