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 grinding machine products, and the size of the workpiece is different, and the machining precision is different. If the grinding wheel speed is not required to be different from the linear speed of spindle grinding machine and only the rotate speed of spindle grinding machine is adjusted, it is difficult to adjust the linear speed of spindle grinding machine to the ideal state.
In addition, due to the stress bending of the grinding machine caused in the shaft machining process, the grinding process will produce different grinding wheel feed torques to the grinding machine, which will bring about different grinding machine changes in terms of grinding wheel output speed/torque, and the corresponding grinding machine will produce vibration knife marks/burning marks, etc., and thus it is difficult to guarantee the grinding accuracy, resulting in low production efficiency and low quality products.
In the process of CNC precision machining, whether the selection of positioning reference is reasonable or not determines the quality of the parts, and has a great influence on whether it can meet the requirements on the dimensional precision and relative position precision 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 benchmark will also affect the complexity of the fixture structure. Therefore, the choice of positioning benchmark is a very important technological issue.
Choose the important surface as the rough benchmark to ensure that the machining allowance of the important surface on the workpiece is small and uniform. The so-called important surface is generally the surface on the workpiece that requires high CNC machining precision and surface quality. For example, the guide rail surface of the lathe and the spindle hole of the spindle box of the lathe are their respective important surfaces. Therefore, when processing the lathe and spindle box, the guide rail surface or spindle hole should be used as the benchmark.
Choose the non-CNC machining surface as the rough benchmark. 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 benchmark. If there are multiple non-machined surfaces on the workpiece, the non-machined surface with higher requirements for the position of the machined surface should be selected as the rough benchmark to meet the requirements and make the shape symmetrical.
The rough benchmark can only be used once in the same size and direction, because the rough benchmark itself is a rough surface that has not been machined, and its surface is rough and low in precision. If it is reused, it will cause a large error.