Establishment of NC Turning Process

When machining parts on CNC lathe, the working procedure should be divided according to the principle of process concentration, and most or all surface processing should be completed as much as possible under one clamping. According to the different structure shapes, the outer circle, end face, inner hole and end face are usually selected for clamping, and the design basis, process reference and programming origin are unified. In batch production, the following methods are commonly used to divide processes.

1. Process division according to the machining surface of parts

That is to say, the part of technological process to complete the same surface is one process. For parts with many and complex surfaces, it can be divided into multiple processes according to its structural characteristics (such as internal shape, shape, surface and plane, etc.).

The surface with high position accuracy requirement is completed under one clamping, so as to avoid the error caused by multiple positioning and clamping affecting the position accuracy. As shown in Figure 1, according to the process characteristics of the parts, the rough and finish machining of the outer contour and the inner contour are respectively completed in one process, which reduces the clamping times and helps to ensure the coaxiality.

2. Process division by rough and finish machining

That is to say, the part of technological process completed in rough machining is an operation procedure, and that part of technological process completed in finish machining is an operation procedure. For parts with large blank allowance and high machining accuracy requirements, rough turning and finishing turning should be separated and divided into two or more processes. Rough turning is arranged on the CNC machine tools with low precision and high power, and the finish turning is arranged on the CNC machine tools with high precision.

This classification method is suitable for parts with large deformation after machining, which need to be separated from rough machining and finish machining, such as the parts whose blanks are castings, weldments or forgings.

3. Divide the process according to the type of tool used

Taking the part of technological process completed by the same tool as one working procedure, this method is suitable for the situation that there are many surfaces to be processed, the continuous working time of the machine tool is long, and the programming and checking of the machining program are difficult.

4. Process division according to installation times

The part of technological process completed at one time is regarded as a working procedure. This method is suitable for the workpiece with few processing contents, and it can reach the state of waiting for inspection after processing.