Measurement uncertainty of generalized stiffness of machine tools

This paper deals with the formulation of a new method of measuring machine tool stiffness. The method enables measurements to be made in generalized coordinates, i.e. measurements of translational and torsional stiffness. It is based on geometrical transformations of a rigid body. It is universal, because it allows any positioning of displacement sensors on the surface of the tested object and to freely transform the excitation force. This allows testing the stiffness of various medium-sized machine tools - lathes, milling machines, etc. The validation of the measurement method (uncertainty budget) and validation of estimated measurement uncertainty are presented. The components of reproducibility and method-specific uncertainties have been shown to contribute significantly more to the budget than the components of metrological characteristics of the sensors used in the measurements. It was also shown which components of complex uncertainty can be omitted from the analysis without losing the accuracy of its estimation. The advantages of the proposed method have been demonstrated on the example of stiffness measurements on a milling machine.