Machining accuracy enhancement by compensating for volumetric errors of a machine tool and on-machine measurement

This paper uses a parameterized error model to analyze machine tool errors within the workspace and the methodology of on-machine measurement for improving the machining accuracy. Based on the rigid body kinematics, positioning errors derived using the homogeneous transformation matrices are parameterized by approximating error components with polynomial functions. Only fourteen measurement points are required to determine the model parameters and obtained from four diagonal measurements. A semi-sphere part was machined for the model verification with and without error compensation, and then measured with a touch trigger probe installed on the spindle while the part still stayed on the machine table. The results showed that the machining errors are reduced about 90, 78 and 92% in x, y, and z axes direction after error compensation. Also, the differences between OMM and CMM data were less than 5 μm, concluding that the parts can be measured on the machine tool with a touch trigger probe with acceptable accuracy.