A comprehensive study on the free vibration of machine tools' hexapod table

Prior knowledge of the free-vibration responses of a hexapod is strongly needed to avoid resonance occurring in the prevailing complicated machining situations. A comprehensive study has been conducted by the authors on the free vibration of machine tools' hexapod table, taking account of the whole kinematic chains. The results have been compared with those obtained from the vibration equations of the moving platform. The second approach entailing fewer equations can yield sufficiently accurate results for vibrations occurring in horizontal planes. The theoretical and finite element method (FEM) results exhibit similar trends of changes and are close to each other. The discrepancies between the results arise mainly from the rotational modes of vibration occurring in vertical planes, which are attributable to the dynamic nature of contact models. A hexapod table possesses distinct vibration modes, including linear vibrations in horizontal planes prevailing in lower modes and rotational vibration in higher modes.