Vibration characteristic of direct drive A/C birotary milling head is analyzed by finite element method（FEM）

former four order vibration mode of the milling’s structure is given

influences to natural frequency of the milling’s structure which comes from swing angle of the A-axis is studied.The natural frequencies when the milling head is working are interval values

the first order natural frequency is（120.48

122.91）

the second order natural frequency is（139.68

142.08）

the third order natural frequency is（328.68

331.9）

the fourth natural frequency is（369.68

372.45）.This colculation provides technological support for design and improvement of this type of milling head.