Abstract: In order to improve the static and dynamic characteristics of vertical machining center,the weak link of machine tool was identified by modal analysis and harmonic response analysis,and it was found that the unreasonable design of the gantry frame structure leads to large deformation of the machine tool in the vertical direction.Aiming at the unreasonable design of the gantry frame,topological optimization and two-dimensional section optimization were used to determine the material distribution;based on MOGA genetic algorithm,the mass,maximum static deformation and first-order natural frequency of the gantry frame were taken as optimization objectives,and the key dimensions of gantry frame were optimized by multi-objective parameters;then,the optimization results were compared with the prototype. The results show that the maximum static deformation of the gantry is reduced by 34.61 %,the mass is reduced by 7.64 %,and the first-order natural frequency is increased by 6.54 %;at the same time,the maximum amplitudes of the whole machine in the X,Y,and Z direction are reduced,and the position of each wave peak has different degrees of backward,the static and dynamic comprehensive performance of the machining center are improved;the optimization effect of gantry frame is verified.

Key words: gantry frame, static and dynamic analysis, multi-step optimization, MOGA, multi-objective parameter optimization