A RAPID IDENTIFICATION METHOD FOR STATIC STIFFNESS OF MULTI-AXIS CNC MACHINE TOOLS

The deformation of machine tools by force affects the machining precision and efficiency directly. This paper proposes a novel method that force-induced error of CNC machine tools with 3 axes was modeled and distribution law of deformation variety in machining space between the ends of machine tool was revealed. A polynomial model of the deformation error for the machine tools is established using the homogeneous coordinate transformation method of multi-rigid-body. To get the coefficients of the model, a ball bar which is used to conduct circular movement testing under loaded condition is designed. Through loading different force on it, the circular motion testing be conducted in XOY, XOZ, and YOZ plane respectively, then the parameters of the model are obtained by identification. According to the model, the deformation error in any direction between the ends of the three-axis CNC machine tools is related to not only the forces in that direction but also the position of the point suffering the force in the machining space, as well as the force values in the orthogonal directions. The research is significance of discovering distribution law of deformation for the machine tools as well as the prediction and compensation of the force-induced error.