Geometric and dynamic evaluation and optimization of machining centers

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

Development of Testing Method of Five-Axis Machining Centres Based on Finishing of Truncated Square Pyramid

Tsutsumi

Saiki²,

Kiotoshi³

et al. 2011

Analysis of NC Data for Machining Test of Cone-Frustum under Simultaneous Five-Axis Control

Kato

Tsutsumi²,

Tsuchihashi³

et al. 2011

NC data for machining the cone-frustum by means of five-axis machining centers with a tilting rotary table are analyzed in detail. The cone-frustum is machined by using a milling cutter at simultaneous five-axis control for inspecting the machining accuracy. However, the NC data have to be changed corresponding to the setting position of the workpiece on the rotary table. Thus, the moving range and velocity of each axis are analyzed by changing the apex angle and center position of the cone. It is found from the analyzed results that the larger apex angle gives the larger moving range and the higher velocity to all axes. When the center position moves along the Y-direction, every reversal point independently appears on a circular path. Therefore, it is recommended to offset the center position of the cone frustum along Y-direction to give the large moving ranges and the high velocities to the axes.

Sensitivity Analysis in Ballbar Measurement of 3D Circular Interpolation Motion Equivalent to Cone-Frustum Cutting in Five-Axis Machining Centers

Kato

2012

This paper describes the testing method for five-axis machining centers using three-dimensional circular interpolation movement equivalent to the cone-frustum cutting. It is assumed in the simulation that a ball bar system is used as a measuring device that can freely moves in 3D space. The ratio of a measurement value by the ball bar and a real error of each axis is defined as a sensitivity coefficient of axis. The sensitivity coefficient of each axis was calculated changing the apex angle and the center location of virtual cone-frustum. The 3D circular movements are simulated, and the effect of the pitch errors of the axes of rotation was investigated by changing the sensitive direction of the ball bar. From the view point of sensitivity coefficient, it is pointed out that if the measurement is conducted by the ball bar which is parallel to the bottom of a cone-frustum whose center is set away from the center line of the axis of rotation, it is possible to measure the movement errors of five axes. は，ISO 規格で試験条件としている半頂角 15°と 45°の 2 種類の円すい台を想定して，テーブル旋回形 5 軸 MC の測定を行うときに使用する NC データを詳細に分析した．そこでは，回転テー