Influence of the Workpiece Crystallographic Orientation on Ultra-Precision Turning of KDP Crystals

Abstract

The mechanical properties of Potassium Dihydrogen Phosphate (KDP) crystal had been relatively well investigated, and it was reported that mechanical properties of KDP crystal are anisotropic corresponding to crystallography orientation. However, the affect of the crystallography orientation to the critical undeformed chip thickness and cutting force variation in ductile mode cutting of KDP crystal are still not clear, which are important in determining proper cutting parameters to get fine finished surface. This paper investigates the influence of crystallographic orientation to critical undeformed chip thickness by a kind of groove cutting on {001} plane, and the influence to cutting force is also researched by face turning. The experiment results demonstrate that the cutting forces and critical undeformed chip thickness for ductile mode cutting varies greatly according to KDP crystallographic orientation. This paper point out that two slipping plane, {110} and {1__,10}, account for the variation of cutting force and critical undeformed chip thickness in different orientation on {001} plane. A set of cutting parameters for ductile mode cutting are selected based on the derived critical undeformed chip thicknesses at different crystal orientations, and overall sooth surface has been achieved on face turned {001} surface, which the roughness is Ra 2.6nm measured by Veeco white-light interferometer.