With the wide use of steam engines and the development of large-scale machinery such as mines, metallurgy, ships and locomotives, more and more metal parts need to be formed and machined. The metal materials used are developed from copper and iron to steel.

However, CNC grinders in Dongguan have a wide range of grinder products, and the size and size of workpieces are different, which require different processing accuracy. Relative to the requirement of grinding machine, grinding wheel speed is different from spindle grinding machine linear speed. It is difficult to adjust the spindle grinding machine speed to satisfy the workpiece grinding machine linear speed. Because of the stress bending of the grinding machine caused by the shaft and rod processing, the grinding process will produce different grinding wheel feed grinding machine torque, which will bring different grinding wheel output speed/torque changes, corresponding grinding machine will produce vibration/burnt grain, grinding accuracy is difficult to guarantee, resulting in low production efficiency, low quality rate and so on.

In Dongguan CNC machining process, whether the selection of positioning datum is reasonable or not determines the quality of parts. It has a great influence on whether the dimensional accuracy of parts can be guaranteed and the accuracy requirements of each other's positions, as well as the processing sequence arrangement between the surfaces of parts. When fixtures are used to install workpieces, the selection of positioning datum will also affect the complexity of fixture structure. Therefore, the selection of positioning datum is a very important process problem.

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 even, the rough datum should be chosen. The so-called important surface is generally the surface which requires high processing accuracy and surface quality on the workpiece, such as the guide surface of the lathe bed and the spindle hole of the lathe spindle box, which are their respective important surfaces. Therefore, when processing the bed and spindle box, the guide surface or spindle hole should be taken as the rough datum.

Choosing non-CNC machined surface as rough datum should generally choose non-machined surface as rough datum in order to guarantee the position requirement between machined surface and non-machined surface. If there are more than one non-machined surface on the workpiece, the non-machined surface with higher requirements for the location of the processing surface should be selected as the rough datum to ensure the requirements and make the shape symmetrical. For the workpiece shown in Fig. 2, the eccentricity between the blank hole and the outer circle is large. The rough reference circle should be the unprocessed outer circle. The workpiece should be clamped in the three-jaw self-centering chuck, and the coaxiality error of the blank can be removed when boring, so as to ensure the uniformity of the wall thickness.

Rough datum can only be used once in the same dimension direction because rough datum itself is a rough surface which has not been machined. Its surface is rough and its accuracy is low. If it is reused, it will produce larger errors.