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

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.