In recent years， the demand for five − axis colltrol machining centers is getting higher and higher to achieve pr （ ⊃ cess integration and high accuracy ． On the uther hand ， it量 s generany difHcult for five − axis control machining centers to realize the same Inotion accuracy as or higher moti 叩 accuracy than three − axis control ones due to the increase ill tw rotary feed axes in addition to three linear feed axes ． Various five − axis Gon 亡rol madhining centers with suitab 工 e constructiens have been developed for their effective purposes ． At that time ， it has beell considered that Trunniorl type 且ve − axis control mach 正 ning centers canrealize the high motion accuracy relatively easily ， based on actual evaluation data and experience ． To make surc this fact ， a five − axis centrol machining center which has Table on − Table type colユstruction ， different from Trunnion type ， was planned in terms of good Qpe 職 bility ． Its mQtion accuracy was measured and con ユpared with the TTunnion type olle by use of DBB 5 meth ｛｝ d． As a result ， it is confinmed that Table − orTab 】 e type five − axis control machining center has higher motion accuracy than Trunnion type one as well as good operability

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This paper proposes a general method for measuring and identifying the geometric deviations inherent to five axis machining centers with a swivel angular head and a rotary table. The structural configuration of this machine is one of mixed five-axis machining centers. If the inclination angle of C axis is an initial value and its angular deviation is also superimposed on it, the inherent geometric deviations are same as multi-tasking machines, which have ten inherent deviations. The circular motion of simultaneous four-axis control around the tilt C-axis is newly proposed in order to measure the circular trajectories and its eccentricities. The measurement of simultaneous three-axis motion around the B-axis is also required to identify the inherent deviations. In this paper, mathematical relationships between geometric deviations and eccentricities of the trajectories are derived and then the procedure for identifying the deviations using the expressions was clarified through numerical experiments. It is also pointed out that six measurements are needed to identify the inherent deviations when the inclination is zero.

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This paper proposes a unique test piece for evaluating the machining performance of five-axis machining centers. A cone-frustum specified by NAS 979 standard has been used as a test piece over 40 years. In this paper, a truncated square pyramid with a half apex angle of 15 degrees is proposed as a test piece for checking the machining performance instead of the cone-frustum. The truncated square pyramid has to be installed on the slope of a fixture which is mounted on the rotary table of the machining centers in order to conduct the machining test under simultaneous five-axis control. Thus, two kinds of fixtures with different mounting angle were prepared for the experiment. The profiles of four side surfaces finished by milling were measured on machine table by an LVDT sensor which is fixed on the spindle head. The contour form of the side surfaces of the test pieces were also measured on a coordinate measuring machine. It is found from both measurement data that the straightness of each side surface, the squareness between adjacent surfaces as well as parallelism can be evaluated by on-machine measurement, and also pitch errors and backlash of tilting rotary tables can be checked. This test method gives much more information compared with the cone-frustum test method.こと指摘した．また，Bossoni らは (6) ，半頂角 45°の円すい台を 30°傾けて，円すい面に垂直にエンドミルを当