An Approach to Estimate the Inherent Deviations by Means of Simultaneous Five-axis Motion K.M. Muditha Dassanayake 1 , Masaomi TSUTSUMI 2 , Kenji HIGASHIYAMA 3 and Ken YAMAMOTO 4 1 Tokyo University of Agriculture and Technology, 2-24-16 Nakacho, Koganei, Tokyo 184-8588， Phone: 042-388-7086, Fax: 042-388-7219 muditha@cc.tuat.ac.jp 2 Tokyo University of Agriculture and Technology 3 Tokyo University of Agriculture and Technology 4 Tokyo Seimitsu Co. Ltd. This paper presents a methodology for identifying the geometric deviations inherent to tilting rotary table type five-axis machining centers by means of the trajectories of continuous five-axis motions. For identification of the geometric deviations, two sets of reference data are prepared by means of a mathematical model. Four deviations were identified accurately by means of the observation equation in which the ball bar measurements and reference data are applied. The remaining four of the eight deviations was identified accurately by means of simple geometric relations. Furthermore, the effect of the fluctuation and backlash of the worm gear rotation on the accuracy level of the method is discussed. The effectiveness of the proposed methodology as an accuracy test is confirmed by the simulation and the experiment. Keywords: Observation equation, Tilting rotary table type, Geometric relations, Systematic deviation 1. Introduction The tilting rotary table type is used to machine comparatively small and precise work pieces and thus vastly used in industries. This tilting rotary table type is the most common model in Japan. This paper presents a methodology based on simultaneous five-axis motion which can be used to identify all the eight deviations [1, 2] inherent to the tilting rotary table type. Ball bar system is used as a measuring instrument. The methodology consists of two calculation steps which supported by two ball bar measurements, achieved at different height levels from the center of the tilting-axis for the rotary table. To achieve the height levels one extension bar which provided with ball bar system is used. Simple mathematical model is used to carry out the simulations for calculations. The effectiveness of the methodology is confirmed by simulation and experiment. The experimental results show the effectiveness of application to the machining centers. Furthermore, this paper discussed the affect of geometric deviations and the backlash of the worm gear on the accuracy level of the identification procedure and also the affect of work origin on motion trajectory which can be used to compensate the four of eight identified deviations. 2. Ball bar measurements and simultaneous five-axis motion 2.1 Ball bar setup and five-axis motion In this research work, a simultaneous five-axis control motion is proposed to evaluate all the static deviations inherent to the tilting rotary table type five-axis machining centers, using a ball bar system [3] as a measuring instrument. The five-axis machine that is the research object is composed of three linear (X, Y and Z) axes and two rotary Z X C Y A Main spindle Work table Z X C Y A Main spindle Work table Z X Y A C L B Y t Z t Center line of A axis Main spindle Ball bar Origin of machine coordinate system O M Z X Y A C L B Y t Z t Center line of A axis Main spindle Ball bar Origin of machine coordinate system O M Fig. 1 Configuration of the machining center Fig. 2 Setup of ball bar (a) at 150 mm (b) at 200 mm Fig. 3 Experimental setup Z X C Y A Main spindle Work table Z X C Y A Main spindle Work table Z X Y A C L B Y t Z t Center line of A axis Main spindle Ball bar Origin of machine coordinate system O M Z X Y A C L B Y t Z t Center line of A axis Main spindle Ball bar Origin of machine coordinate system O M Fig. 1 Configuration of the machining center Fig. 2 Setup of ball bar (a) at 150 mm (b) at 200 mm Fig. 3 Experimental setup