Geometric accuracy of grinder:
It refers to the movement accuracy and mutual position accuracy of each part without bearing the load. It is impossible to make a machine tool absolutely accurate, and there are always more or less inevitable errors. This kind of error will be reflected to the workpiece to varying degrees during the processing of the workpiece, and affect the processing accuracy of the workpiece. Generally, there are radial runout and axial runout of the main shaft, the straightness of the movement of moving parts such as the worktable, and the mutual position error and transmission error of the working parts.
The radial and axial movement of the grinding wheel spindle and the large movement error of the headstock of the grinding machine not only affect the surface roughness of the workpiece after grinding, but also cause the workpiece to produce roundness and end face beating, resulting in uneven sparks during the grinding process. When the worktable moves on the vertical plane, it affects the linearity of the workpiece generatrix on the internal and external cylindrical grinders, and the plane is ground on the surface grinder, resulting in large errors in the flatness of the workpiece.
The center line of the grinding wheel spindle shaft of the external cylindrical grinder and the center line of the grinding wheel shaft of the internal cylindrical grinder are not equal to the center line of the workpiece headrest axis. When grinding the inner and outer cones, the workpiece generatrix is a hyperbola. The center line of the spindle axis of the grinding wheel is not parallel to the moving direction of the worktable, which affects the flatness of the end surface of the workpiece after grinding. The transmission error of the grinder has a great influence on the machining accuracy of thread grinding and gear grinding.
The stiffness of the grinder:
It refers to the ability of the parts to resist deformation when the grinder bears external force (grinding force). That is, under the same grinding force, the smaller the deformation of the part, the greater the rigidity. On the contrary, the deformation of the component is large, which means that the rigidity of the component is small. The magnitude of these deformations destroys the original static geometric accuracy of the grinder, and will cause the size of the machining error of the workpiece. Therefore, the machine tool with good rigidity has high machining accuracy of the workpiece.
The heat source inside the grinder is unevenly distributed, and the amount of heat generated by each part in the movement is also different. The influence of external heat source on each part of the machine tool is also different. The thermal expansion coefficient of the parts is different due to different materials, resulting in different parts of the machine tool. The slight deformation reduces the original geometric accuracy of the machine tool and affects the machining accuracy of the workpiece. Therefore, the precision grinder should be installed in a constant temperature room to prevent temperature changes from affecting the accuracy of the machine tool and workpiece.
Crawling of moving parts of grinder
When the moving parts such as the grinding wheel frame of the grinding machine worktable are fed in a micro cycle or continuously move at a low speed, the phenomenon of uneven movement occurs, which is generally called 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.
Vibration of the grinder
The grinding machine vibrates during the grinding process, causing the relative position of the grinding wheel and the workpiece to periodically change, causing vibration marks on the surface of the workpiece, which seriously affects the processing quality and accuracy.
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 positioning datum, clamping method, selection and correct repair of grinding wheel, and reasonable selection of grinding amount and process method during workpiece processing.