The stiffness of CNC grinding machine refers to the ability to resist deformation under the action of cutting force and its residual force. The design of grinding machine needs high static stiffness and dynamic stiffness. In the grinding process of CNC surface grinder, the static bearing capacity of grinding, moving parts and parts processing quality in the grinding process; Dynamic bearing friction resistance, cutting force, inertia force. The structural parts of the machine tool will be deformed, and the machining error of the workpiece will be reduced under the action of these forces. In order to enable the machine tool to achieve high structural stiffness and obtain qualified workpieces, and for the needs of subsequent structural design, the structural form of components shall be selected:

(1) Select the shape and size of the section

With the same cross-sectional shape and the same cross-sectional area, the arm thickness should be reduced and the section should be increased to make the cavity made of the supporting member of the machine bed. The torsional stiffness of square section is smaller than that of circular section, and the flexural stiffness of circular section is smaller than that of square section. Therefore, the parts bearing torsional load such as shaft must be made into a circle, and the parts bearing bending load such as bed must be made into a square. The stiffness of the non closed section is much smaller than that of the closed section, so the closed bed is adopted.

(2) Local stiffness of members

The stiffness of the connecting members of the guide and support grinder is the weakest part, so the connection mode has a great influence on the local stiffness. In my design, the x-axis guide rail is relatively, so the double arm connection is used to improve the local stiffness.

(3) Components with welded structure

All supporting parts of NC grinder are welded with steel plate and section steel, which reduces the quality and improves the stiffness.

Use steel plates and sections instead of castings:

① The elastic modulus of steel is twice that of cast iron. If the shape and outline dimensions are the same, the stiffness of weldment and casting must also be the same. The wall thickness of weldment of steel plate and section stiffness can meet the requirements by half of that of casting.

② As long as the local stiffness is the same, only the local stiffness is directly proportional to the third power of the arm thickness, and the arm thickness of welded parts with steel plate and profile stiffness is only about 80% of that of the casting.

③ Steel can increase the resonant frequency of components and is not easy to resonate.

④ Steel plate welding can make it into a fully closed box to improve the stiffness