Abstract:To satisfy the requirements of distributing the dynamic stiffness of machine tool joints,an optimization design method for dynamic stiffness of machine tool joints based on the theory of modal flexibility was proposed.Weak modes that had significant effects on dynamic characteristics of the machine tool were judged according to modal flexibility coefficients of those modes. The multi-objective optimization mathematical model was established,with the minimum modal flexibility of the weak modes being the objective functions.To increase the efficiency of optimum calculations，the orthogonal experiment design and the grey relational analysis(GRA) method were introduced.Taking a precision horizontal machining center as example,the method was applied to the dynamic stiffness optmization design of the linear guide,ball screw,and bolt joints of the column-spindle system.The linear guide joint in the X-axial direction was identified that it has the most significant influence on dynamic characteristics of the machine tool.The best solution of dynamic stiffness of joints was obtained.The effectiveness and engineering practicability of the proposed method were verified by the results of numerical simulation and experiments.