Study on Geometric Error Model of CNC Machine Tools under Actual Working Condition

The machining error of CNC machine tools comes from the positional error between the workpiece and the tool, which is generally predicted and compensated by the geometric error model. However, the currently established geometric error model based on multi-body kinematic theory cannot consider the shape and position errors of the parts comprehensively. Therefore, this paper proposed a geometric error model that can consider the actual working conditions of machine tools. The model characterized the geometric elements of the parts with discrete coordinate point sets, and determined the error transfer relationship between the geometric error of the parts and the geometric error of the whole machine through the method of determining the equivalent mounting datum at the three highest points and the actual assembly process, and predictsed the relative positional error of the tool and the workpiece under the actual working conditions. In this paper, the geometric error model of Y-axis motion was established by taking the horizontal axis of a vertical machining center as an example. Based on this, the correctness of the established geometric error model was verified by the test experiments on this vertical machining center.