(1) Geometric accuracy of the grinding machine. The geometric accuracy of the grinding machine refers to the motion accuracy and mutual positional accuracy of each component without being subjected to load. It is impossible to make the machine tool absolutely accurate, and there is always an inevitable more or less error. This kind of error will be reflected to the workpiece to varying degrees during the machining of the workpiece, which will affect the machining accuracy of the workpiece. Generally, there are radial runout and axial sway of the main shaft, straightness of movement of moving parts such as worktable, mutual position error of working parts and transmission error.
The radial runout and axial sway of the grinding wheel spindle and the movement error of the grinding head frame not only affect the surface roughness of the workpiece after grinding, but also cause the workpiece to have out-of-roundness and end face runout, resulting in uneven spark during grinding. . When the table moves not perpendicular to the vertical plane, the inner and outer cylindrical grinding machines affect the linearity of the workpiece busbar, and the plane is ground in the surface grinder, resulting in a large flatness error of the workpiece. The center line of the grinding wheel spindle shaft of the cylindrical grinding machine and the center line of the inner grinding wheel shaft axis are not equal to the center line of the workpiece head frame. When the inner and outer cones are ground, the workpiece bus bar is hyperbolic. The center line of the spindle shaft of the grinding wheel is not parallel to the moving direction of the table, which affects the straightness of the end face of the workpiece after grinding. The transmission error of the grinding machine has a great influence on the machining accuracy of thread grinding and gear grinding.
(2) The rigidity of the grinding machine. It refers to the ability of the parts to resist deformation when subjected to external forces (grinding forces). That is, in the case of the same grinding force, the smaller the deformation of the part, the greater the rigidity. Conversely, the component is deformed greatly, indicating that the component is less rigid. The magnitude of these deformations destroys the static geometric accuracy of the grinder and will cause the machining error of the workpiece. Therefore, the machine tool with good rigidity has high processing precision.
(3) Thermal deformation. The heat source inside the grinding machine is unevenly distributed, and the heat generated in each part is different. The external heat source has different effects on various parts of the machine tool. The thermal expansion coefficient of the parts is different due to different materials, which causes different parts of the machine tool. The slight deformation makes the original geometric accuracy of the machine tool decrease, which affects the machining accuracy of the workpiece. Therefore, the precision grinding machine is preferably installed in a constant temperature chamber to prevent temperature changes from affecting the accuracy of the machine tool and the workpiece.
(4) The moving parts of the grinding machine crawl. When the moving parts such as the grinder table grinding wheel frame are used for micro-period feeding or low-speed continuous movement, the phenomenon of uneven movement occurs, which is commonly called crawling. When this phenomenon occurs in the grinding machine, the feeding during the grinding process is uneven, which affects the surface roughness of the workpiece.
(5) Vibration of the grinding machine. The grinding machine generates vibration during the grinding process, causing periodic changes of the relative position of the grinding wheel and the workpiece, causing vibration marks on the surface of the workpiece, which seriously affects the processing quality and precision.
In order to improve the accuracy of the workpiece after grinding, in addition to trying to eliminate the influence of the above factors, we must also pay attention to the reasonable selection of the positioning reference during the machining of the workpiece, the clamping method, the selection and correct repair of the grinding wheel, the reasonable selection of the grinding amount and the processing method.
