Generation of a 3D error compensation grid from ISO 230-1 error parameters obtained by a SAMBA indirect calibration and validated by a ball-bar spherical test

Abstract

Tool path deviation reduces machined parts quality. To enhance machine tool accuracy, compensation tables are provided in most controllers to automatically apply small corrections to axis commands. A model-based approach, considering the ISO 230-1 machine geometric error parameters, is proposed to generate the table entries. The error parameters are estimated using model-based indirect calibration results from a scale and master balls artifact probing (SAMBA) test. Two models are used, one with primarily the axis alignment errors and scale errors and the other including many error motions. The 3D grid error compensation is generated with a minimal optimum mesh grid dimension to achieve a preset precision considering the estimated model error parameters. The efficiency of the table is evaluated using a 3D ball-bar test consisting of various circular trajectories along several meridians and the equator before and after applying the table-based error compensation. It is shown that the volumetric errors due to out-of-squareness errors and linear axis linear positioning errors can be compensated using a 2 × 2 × 2, 8 nodes, grid. However, when including error motions, the optimum grid dimension depends on the specific error values of the machine. For the tested machine, a 19 × 19 × 19 for 6859 nodes grid was required, with which the out-of-sphericity of the tool trajectory relative to the workpiece frame is improved by over 82%.