Abstract: To improve the machining accuracy of machine tool, the geometric error compensation for threeaxis vertical machining center was studied through error compensation. Based on the idea of hierarchical compensation, analyzing the feature of the structure of machine tool and using geometric error compensation module in a commercial CNC system (SIEMENS 840D), the geometric errors of the machine center were divided into compensable errors and uncompensable errors and an error model for compensation was established according to the compensable errors. An experiment was carried out in 0540D threeaxis vertical machining center. The results show that the kinematic accuracy after compensation is improved.

Key words: machine tool, error compensation, geometric error, CNC system