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Effect of Grinding Accuracy on Machining Accuracy of Workpiece

Mar 10, 2018

Grinding machine geometric accuracy, stiffness, thermal deformation, motion stability and vibration resistance, etc., will directly affect the workpiece machining accuracy.

 1. The geometric accuracy of the grinding machine refers to the accuracy of movement and the mutual position accuracy of each component when the load is not applied. It is impossible to make machine tools absolutely accurate, and there are always more or less errors. This error will be reflected to the workpiece in varying degrees when processing the workpiece, and affect the accuracy of its workpiece processing. Generally, there are radial runout and axial turbulence of the spindle, the straightness of the moving parts such as the table, the mutual position error of the working parts, and the transmission error. The radial runout and axial turbulence of the grinding wheel spindle and the error of the head movement of the grinder are large, which not only affects the surface roughness of the workpiece after grinding, but also causes roundness and end surface runout of the workpiece, resulting in non-uniform spark during grinding. When the worktable moves in the vertical plane is not vertical, the internal and external grinding machines affect the linearity of the workpiece busbar. Grinding the plane in the surface grinder causes the flatness error of the workpiece to be large. The center line of the grinding wheel spindle shaft of the cylindrical grinding machine and the grinding wheel grinding shaft axis of the cylindrical grinding machine are not equal to the center line of the workpiece headstock shaft. When grinding the inner and outer cones, the workpiece bus is a hyperbola. 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 workpiece surface 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 the grinder is subjected to external forces (grinding forces). That is, in the case of the same grinding force, the smaller the component deformation, the greater the rigidity. On the contrary, the large deformation of the parts means that the rigidity of the parts is small. The size of these deformations destroys the static geometrical accuracy of the grinder and will cause the size of the workpiece's machining error. Therefore, the machine tool with good rigidity has high machining accuracy.

 3. The heat source inside the thermal deformation grinder is unevenly distributed, and the heat generated in the various parts is also different. The influence of the external heat source on various parts of the machine tool is also not the same. The thermal expansion coefficients of the parts are not the same due to different materials. The different micro-deformation of each part reduces the original geometric accuracy of the machine tool and affects the machining accuracy of the workpiece. Therefore, precision grinders are best installed in a constant temperature chamber to prevent temperature changes affecting the accuracy of the machine and the workpiece.

 4. Grinding machine moving parts crawling Grinding machine table wheel frame and other moving parts in the micro-cycle feed or low-speed continuous movement, the phenomenon of uneven movement, known as crawling. When this phenomenon occurs in the grinding machine, the feed during the grinding process is not uniform and the grinding surface roughness of the workpiece is affected.

 5. Grinding machine vibration Grinding machine produces vibration in the grinding process, so that the relative position of the grinding wheel and the workpiece occurs periodic changes, so that the surface of the workpiece to generate chatter marks, seriously affecting the processing quality and accuracy. To improve the accuracy of the workpiece after grinding, in addition to efforts to eliminate the influence of the above factors, we must also pay attention to the reasonable selection of the positioning reference, the clamping method, the selection and correct repair of the grinding wheel, the reasonable choice of grinding amount and the processing method during the processing of the workpiece. .