Development of Form Rolling Technology for High Precision Worm Using the Rack Dies of Counter Flow Type

摘要

The technology to produce high precision worm in form rolling is described in this study on the base of three-dimensional FE-simulation and its confirmation by experiment. It is important to determine the initial blank diameter in form rolling because it affects tooth quality. The calculation method of the initial blank diameter is suggested and it is verified by two-dimensional FE-simulation. Form rolling process of worm shaft used as automotive part using the rack die of counter flow type is considered and simulated with the same numerical model as actual process by three-dimensional FE-simulation. Generation process of tooth profile during the form rolling by the rack die of counter flow type is investigated from the result of simulation. The experiments using both the rack die and the round die are performed under the same conditions as those of simulation. The results of simulation and experiment indicate that the form rolling process of worm shaft using the rack die is decidedly superior to that using the round die from the aspect of the precision of worm such as the surface roughness, the straightness and the profile of worm.