Digital program-controlled contour systems are widely used in milling machines, including simple, reliable and inexpensive phase systems with a wide range of process capabilities. These systems are used in many factories, especially to control the machining of precision machine parts with large vertical surfaces. Correct programming of control program is one of the main conditions to ensure the machining quality of precision machine parts. For digital program-controlled phase system, the preparation of control program is carried out by the use of automatic program-controlled preparation system, and its quality level depends largely on the price of the preparation control program. The other is the machining error caused by manual control of the equipment, including the accidental error and systematic error of the process system.

All the machining errors in the system error plays a major role, for precision machinery parts as a whole, will cause a series of NUMERICAL control process system error, which mainly has the following aspects: 1. Clearance. The result is similar to the insensitive belt in the transmission chain of machine tools, but does not include the gap 2 in the reverse transmission chain. Amplification factor of unstable drive. 3. Phase error recorded on control program tape. 4. Periodic step instability of sensor feedback is mainly in the form of phase instability. At the same time, it should be pointed out that the discontinuity of transmission is the cause of the corrugability error of the machining system, and the error is more obvious in the machining of the straight line segment with a small Angle between the arc segment and the coordinate axis, because any curve contour can be regarded as the combination of the straight line segment and the arc.