NC machining of gears is an effective way to improve gear accuracy and machining efficiency. It is one of the main development trends of gear machining. The most commonly used gear machining method is continuous generation method, which is typically represented by gear hobbing, worm grinding wheel grinding and gear shaping. The outstanding feature of the continuous generation method is that the tool workpiece relationship needs to be strictly determined, that is, the meshing relationship between the gear like tool and the gear workpiece to be machined. With the tool feeding along the axial direction of the workpiece, the workpiece axis needs to be superimposed with additional motion, which is usually called differential motion. The common general NC system does not have the effective countermeasures of the above two aspects, so it is not suitable for gear NC machining. In addition, the motion relationship of gear machining process is complex, so it is impossible to program directly with the standard NC language for tool center trajectory. A different programming language must be designed. The most effective countermeasure in this regard is to program from gear design parameters and machining tool parameters.

To sum up, the gear processing system must at least break through the following three difficulties:

1) Synchronous phase locking: to ensure the strict constant ratio relationship between tool and workpiece;

2) Electronic differential synthesis: realize the proportional synthesis parameters of two or more independent motions;

3) Automatic programming: realize the transformation from original parameters of gear machining to NC machining program.

This paper briefly introduces the Countermeasures of the above three difficulties and the successful gear cutting system developed on this basis.