Study on the Reason of Static Stiffness of the Whole Machine in Non-Circular Phenomenon When Vertical Machining Center Milling Circle

Abstract

Aiming at the phenomenon that the tool-work-piece offset causes the milling to be non-circular during the circumferential milling of CNC machine tools, the reason of the static stiffness of the whole machine is studied. In this paper, a vertical machining center is taken as the research object. Based on the multi-body system theory and the homogeneous coordinate transformation, the deformation modeling of the whole machine is carried out. The force deformation in the direction of X, Y and Z is analysed. The static stiffness coefficient method is used to integrate and modify the deformation in the direction of X, Y and Z. Finally, the mathematical model of the static stiffness of the whole machine is derived. After the research, it is found that in the same direction, the static stiffness of the tool branch chain and the work-piece branch chain are different, resulting in different deformation of the whole machine; the static stiffness of the tool branch chain and the work-piece branch chain in the X and Y directions is different, and finally the circumferential milling is non-circular. It lays a certain theoretical foundation for the design optimization of CNC machine tool components and the improvement of the static stiffness of the CNC machine tool. It provides reference for other types of CNC machine tool static stiffness modelling, has a guiding significance.