A DBB-based accuracy measurement method for rotary axes of high speed 5-axis CNC machining center

The equipment of 2 rotary axes on 5-axis CNC machining centers provided 2 more degrees of freedom (DOF) between the workpiece and the tool, as well as more geometrical errors. There was not authoritative method to measure the alignment errors of rotary axes. A novel method was proposed in this paper to assess the main alignment errors of C-axis of 5-axis CNC machining center by using double-ball-bar (DBB). First, the measurement models were derived, which contained four main errors of C-axis, during the measurement, several axes moved together in order to keep the DBB follow a circle trajectory, and during this process, the length changes of the bar were send to the PC which connected with the sensor equipped in DBB. The errors were analyzed and calculated with the length changes of the bar of DBB at different sensitive directions. At the end of this paper, the synthetical errors of the machining center were proposed as the ultimate result. The applicability and effectiveness of this proposed diagnosis method was validated by comparing the calculated results and the real errors existed in the aim 5-axis machining center.