Abstract: Owing to the precision machining of dual lead modification profile ZN worm (also called straight sided normal worm), it is necessary to study a forming grinding method. In traditional grinding method of modification profile worm, the grinding wheel is modified by manual operation according to processing experience. Aiming at forming grinding of modification profile ZN worm, the profile modification is analyzed on normal plane of worm. The mathematical model of grinding and tooth modification profile are established, while the forming grinding wheel section profile is calculated by space meshing theory. The grinding wheel is trued and dressed by a NC dressing device according to the section profile. An applied dual lead modification profile ZN worm is selected as an example to verify the forming grinding effect. The grinding experiment is fulfilled by a self-developed NC dressing system and a worm grinder in a factory. The results show that this method has achieved the worm tooth modification profile, meanwhile the worm tooth shape accuracy reaches level 6. It can satisfy the high-precision forming grinding of dual lead modification profile ZN worm.

Key words: Dual lead ZN worm, Form grinding, Grinding wheel truing and dressing, Modification profile