Abstract: There are many joints in the machine tool and each joint has different dynamic stiffness under different contact conditions, when conduct the optimization it is difficult to study how each dynamic stiffness affects the dynamic characteristics of machine tool. To solve the problem, an optimal configuration method of dynamic stiffness of machine tool joints based on orthogonal experiment is proposed. The weak modes and joints are determined based on the modal flexibility and elastic energy distribution theory. Then a multi-objective optimization model is established, in which dynamic stiffness of each weak joint is regarded as the design variable and the minimum modal flexibility of each weak mode is regarded as the objective. An orthogonal experiment method is adopted to improve the optimization efficiency, and theory of similarity priority ratio is introduced in the results analysis to conduct the collaborative optimal configuration of the joints dynamic stiffness. The optimal configuration method is applied in a vertical machine center. The simulation shows that the modal flexibility of each weak mode is decreased obviously after the optimization, and then the dynamic characteristic of the whole machine tool is improved. Thus this optimal configuration method is verified to be feasible.

Key words: dynamic stiffness optimal configuration, joints, modal flexibility, orthogonal experiment, similar priority ratio