The process principle of floating die is shown in the figure. It was first put forward in 1987 when scholars such as tuncer C of British University of brightham studied the precision forging process of hollow parts. In the forming process, when the punch is pressed down, the die can move downward with it. At this time, the blank moves upward relative to the die. The friction between the blank and the die changes into an effective power to promote the metal flow, which reduces the metal flow resistance, improves the metal fluidity, and reduces the forming load to a certain extent.
British scholars T.A. Dean and M.H. Sadeghi have made a comprehensive and systematic study on the forming of spur gear by using the floating die process. Through the optimal design of preform shape and die structure, the laws of ejection, forming load, dimensional accuracy and tooth filling in the forming process of spur gear are compared and analyzed. The forging tooth profile obtained by experiment and the corresponding tooth profile of final forging die are compared and analyzed.
Cai. J. T.A. Dean et al. Comparatively analyzed and studied the forging process of spur gear with fixed die structure and floating die structure. The limit load of forming spur gear with fixed die structure is 21% higher than that with floating die structure. Using the floating die process, the punch and the die move downward together, which effectively reduces the friction resistance between the die and the metal blank surface, and also reduces the wear and load of the punch.
Tan Xianfeng, Liu Xia and others simulated the punching upsetting extrusion process of spur gear with fixed die and floating die by using finite element simulation software. The quality defects of metal blank in the forming process and the effects of process parameters such as friction coefficient, pressing speed, blank shape and size and die fillet radius on tooth filling are compared and analyzed. The research shows that the floating die is not only conducive to the filling of the tooth corner of the die cavity, but also can significantly reduce the load at the end of forming.
Yang Cheng, Zhao shengton and others believe that the distribution of radial friction during the filling of precision forged tooth profile of spur gear is the main reason for the difficulty of filling the top and bottom of precision forged tooth profile. By changing the movement speed of the floating die, the stress distribution in the deformation area of the metal blank can be changed, so as to improve the filling of the top and bottom teeth.
Cheng Yu et al. Adjusted the movement mode of the floating die in the forging process on the basis of the ordinary floating die, first upward and then downward, so as to make the tooth shape of the upper and lower ends of the gear blank fill evenly. It can obtain spur gear parts with good filling under lower forming load than ordinary floating die structure.