As shown in Fig. 1, the tooth surface of the modified helical gear obtained by changing the center distance is seriously distorted, so it is necessary to reduce and improve the tooth surface. Therefore, by modifying the drum profile of the cutter tooth direction and then the helical gear tooth direction, adjusting the diagonal feed coefficient to improve the tooth surface distortion, it is known that there is an optimal diagonal feed coefficient of:
In the formula, the cutter and gear take positive in the same direction and negative in the reverse direction. Taking the small and medium-sized gear with gear parameters as an example, the relationship between the diagonal feed coefficient and the twist coefficient is calculated, as shown in Fig. 2. With the increase of the diagonal feed coefficient C, the twist coefficient r of the tooth surface of the modified helical gear first increases and then decreases. When the optimal diagonal feed coefficient is-3.256, the maximum value of the tooth surface twist coefficient r is 0 At this time, the distortion degree of tooth surface is the minimum, which is close to eliminating the distortion. Therefore, the tooth surface distortion can be effectively improved by grinding or hobbing the diagonal worm, by modifying the cutter and adjusting the diagonal feed coefficient.