The planetary rolling process of forming the internal thread

Forming process of internal thread is an advanced manufacturing process. A new planetary rolling process for forming the internal thread is proposed. The structures of rolling system and working process are described in detail. The finite element model of forming internal thread is established, and the forming experiments are conducted by a homemade experimental rig. The material displacement, microstructure, strain, and microhardness are investigated by finite element model and experiment. The results show that the formed internal thread meets requirements and the results of simulation and experiment are consistent. Through the planetary rolling process, the microstructure is stretched and forms the fibrous tissue at the bottom of tooth space of the internal thread. The maximum deformation is located at the bottom of tooth space, and the deformation characteristics are corresponding to the microstructure distribution. At the bottom of tooth space, the microhardness and the equivalent strain are also largest. The maximum microhardness of formed internal thread is improved 37.6%. The new planetary rolling process can improve the production performances and simplify the processing equipment.