Functional accuracy investigation of work-holding rotary axes in five-axis CNC machine tools

Rotary axes error motions of five-axis CNC machine tools affect dimensional, geometrical and form accuracy of machined features according to structural design and sensitive direction considerations. Work carrying kinematic chains mostly use one rotary axis in radial Fixed Sensitive Direction (radial FSD) setup. The application keeps workpiece axis coaxial with the axis of rotation, preparing more flexibility for machining of complicated features. In spite of conspicuous advantages, in case of poor geometrical quality of machined features, lack of knowledge about error patterns makes the error source isolation process more difficult. This paper investigates the consequences of cycling error motions of radial FSD work-holding rotary axes, in order to prepare intuitive knowledge about possible error patterns. A virtual cutting module equipped with an error-mapping model is generated to simulate the cutting process in vicinity of different error motion scenarios. As a novel approach, comparison of measured deviations with available error patterns facilitates the error source isolation. Experimental results conducted on airfoil cutting process verified the effectiveness of the presented method.