Evaluation of Geometric Deviations Inherent to 5 Axis Machining Center Based on Checkered Pattern of Machined Surface Using Ball End Milling

Generally, ball bar instruments are used for the calibration of 5 axis machining centers. Also, some evaluation techniques using the R-test and tracking interferometer have been proposed. As those measurement instruments are expensive, the test method of machining accuracy that doesn't need special instruments is useful for the users of machine tools. In this study, a test method of machining accuracy is proposed for 5 axis machining centers. The test method uses the checkered pattern milling proposed for conventional three axis machining centers. In the checkered pattern milling for 5 axis machining centers, the hollow grooves are machined with a ball end mill in one direction. After that, the finished surface of the workpiece is painted, and the hollow grooves in orthogonal direction are machined by the simultaneous three-axis control motions of one rotary axis and two linear axes. The influence of the eight geometric deviations inherent to the tilting rotary table type 5 axis machining center on the checkered pattern is investigated by a simulation. As a result, when the four deviations exist separately in the 5 axis machining center, the checkered pattern changes individually at the checked intersections. Also, a new test method that is based on the checkered pattern milling for 5 axis machining centers is proposed. The new test method can evaluate all eight deviations to distinguish difference in the checkered pattern.