（1） It can be expressed by diameter value programming or radius value programming and radius value programming.
The default programming mode of the CNC system is diameter value programming, which is because the radial dimensions of the processed parts are expressed by diameter value when they are measured on the drawing, so it is most convenient to use diameter value programming, that is, in the diameter direction, when absolute value programming is used, X is indicated by diameter value; When programming with increment value, it is expressed as twice of the actual radial displacement and attached with direction sign (positive direction can be omitted).
（2） Absolute value programming, incremental value programming or mixed programming are used to mark the dimensions according to the drawings of the processed parts. From the point of view of programming convenience, in a program section, absolute value programming, incremental value programming or mixed programming are used. When programming in absolute coordinates, the coordinate words X and Z are used; when programming in incremental coordinates, the coordinate words u and W are used.
（3） Most CNC lathes have the function of tool automatic compensation, which can realize the compensation of tool tip radius, tool wear and the position error when installing the tool. Before CNC precision machining, the operator only needs to input the relevant compensation value into the specified memory, and the CNC system can automatically compensate the cutter. There is no need to change the machining program no matter the radius of the tool tip arc, the tool wear or the change of the tool position, so the programmer can program according to the actual contour size of the workpiece.
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