Machine tool structure design based on the coupling analysis of dynamics and cutting performances

Cutting performance is one of the most important factors to judge the numerical control (NC) machine tool, therefore it should be considered at the design stage. A structural design method, considering the requirements of both dynamics and cutting performance was introduced in order to promote the overall performance of a 4-axis milling machine developed by the laboratory. According to the chatter theory in machining, the three dimensional chatter stability chart (spindle speed-width of cut-depth of cut) and chatter frequency chart (spindle speed-width of cut-chatter frequency) were predicted after acquiring the frequency response function (FRF) at the tool tip and the cutting coefficients from the experiments. The experimental modal analysis was employed to test the machine. The cause of chatter occurrence, which is resulted from the inappropriate design, can be figured out based on the obtained visualized modal shape of the machine. The parallel spindles head of the machine was then modified and the comparison of tool tip FRFs shows that the dynamic stiffness of the target mode is increased by 28.2%, which is beneficial to the chatter resistance.