The section shape and size of the foundation part are designed reasonably, and a reasonable rib plate structure is adopted. Under the action of external force, each foundation part will bear bending and torsion load, and its bending and torsion deformation depends on the bending and torsion inertia moment of the foundation part. Bending and torsion moment of inertia is large, but the deformation is small and the stiffness is high. Table 5- 1 lists the moments of inertia of different cross-sectional shapes and sizes with the same cross-sectional area (that is, the same weight). According to the data in the table, under the same shape and cross-sectional area, reducing the wall thickness and increasing the cross-sectional outline size can greatly increase the stiffness; The stiffness of closed section is much higher than that of non-closed section. The torsional stiffness of circular section is higher than that of square section, while the bending stiffness is lower than that of square section. Rectangular section has high bending stiffness in the direction of large size. Therefore, the structural static stiffness of the foundation can be greatly improved by reasonably designing the cross-section shape and size. The static stiffness of machine tool structure refers to the ability of machine tool to resist deformation under the action of cutting force and other forces. Machine tools are affected by many external forces during machining, including the self-weight of moving parts and workpieces, cutting force, driving force, inertia force during acceleration and deceleration, friction resistance and so on. Under the action of these forces, all parts of the machine tool will be deformed, such as bending and torsion deformation of the basic parts, local deformation of the supporting members, contact deformation of the fixed connecting surface and the moving meshing surface, etc. These deformations will directly or indirectly cause the relative displacement between the tool and the workpiece, destroy the original correct position of the tool and the workpiece, and thus affect the machining accuracy of the machine tool and the characteristics of the cutting process. Therefore, improving the static stiffness of machine tools is the general requirement of machine tool structural design. The high efficiency, high power and high speed of CNC machine tools make the external load it bears worse, and the automation of machining process makes the machining error unable to be corrected and compensated by manual intervention. Organ telescopic protective cover telescopic screw protective cover DGT catheter protective cover ammonia nitrogen online analyzer, so the deformation of CNC machine tools will have a serious impact on machining accuracy. In order to ensure stable and high precision of CNC machine tools under automatic and efficient cutting conditions, its mechanical structure should have high static stiffness, and there are standards that the stiffness coefficient of CNC machine tools should be 50% higher than that of similar ordinary machine tools.