Investigation of anisotropic mechanisms in ultra-precision diamond machining of KDP crystal

Potassium dihydrogen phosphate (KDP) crystal presents a host of problems to engineers and opticians. Moreover, because of its anisotropic character, a particular crystal orientation and plane wave transmission are required while the machining process is performed. In this study, by applying the principle of the maximized shearing deformed specific energy and the different shearing elastic modulus along different crystal planes and orientations, a theoretical model to calculate the shear angles when cutting KDP crystal was established. Based on this model, the shear angles’ variation regularity under different cutting conditions was obtained. Additionally, the variation regularities of cutting forces and roughness on different crystal planes were discussed. The results indicate that on different crystal planes the average cutting force and roughness as well as their variation amplitude are different. In addition, the calculated results show that rake angle plays an important role on suppression and minimizing material anisotropic character. Furthermore, the ultra-precision turning and milling experiments were conducted, and the theoretical model matched the experiments well within normal operating conditions.