With the widespread use of steam engines and the subsequent development of large-scale machinery such as mines, metallurgy, ships and locomotives, more and more metal parts need to be formed and cut. The metal materials used have evolved from copper and iron to steel.


However, the CNC machining industry has a wide variety of grinder products, and the size of the workpiece is different, and the machining accuracy is different. Compared with the grinding machine, the grinding wheel speed is different from that of the spindle grinding machine. It is difficult for the grinding machine to adjust the spindle grinding machine speed to meet the workpiece grinding machine processing linear speed to the ideal state. In addition, due to the stress bending of the grinding machine caused by the machining process of the shaft, the grinding process will produce different torques of the grinding wheel feed to the grinding machine, which will bring about the grinding wheel output speed/torque different grinding machine changes, and the corresponding grinding machine will produce vibration knife marks/burning marks, etc. , Grinding accuracy is difficult to guarantee, resulting in low production efficiency and low quality rate.





In the CNC machining process, whether the selection of positioning reference is reasonable or not determines the quality of the parts, whether it can guarantee the dimensional accuracy and mutual position accuracy requirements of the parts, and the processing sequence arrangement between the surfaces of the parts. When using a fixture to install the workpiece, the choice of positioning datum will also affect the complexity of the fixture structure. Therefore, the choice of positioning datum is a very important process issue.


Choosing the important surface as the rough datum is to ensure that the machining allowance of the important surface on the workpiece is small and uniform, and the surface should be selected as the rough datum. The so-called important surface is generally the surface on the workpiece that requires high machining accuracy and surface quality. For example, the guide rail surface of the bed and the spindle hole of the headstock of the lathe are all important surfaces of each. Therefore, when processing the bed and spindle box, the guide rail surface or spindle hole should be used as the rough reference.


Choosing the non-CNC machined surface as the rough datum In order to ensure the position requirements between the machined surface and the non-machined surface, generally the non-machined surface should be selected as the rough datum. If there are multiple unprocessed surfaces on the workpiece, the unprocessed surface with higher requirements for the position of the processed surface should be selected as the rough reference to ensure the requirements and make the shape symmetrical. For the workpiece as shown in Figure 2, the eccentricity between the blank hole and the outer circle is large, and the unprocessed outer circle should be selected as the rough reference, and the workpiece should be clamped in the three-jaw self-centering chuck to adjust the coaxiality of the blank The error is removed when boring, so as to ensure the uniform wall thickness.


The rough datum can only be used once in the same size direction. Because the rough datum itself is a rough surface that has not been machined, its surface is rough and the accuracy is low. If it is reused, it will cause a large error.