Evolution of The Conventional Rotary Forging Machines to Six-DoF Parallel Kinematics Machines

Rotary forging is an incremental bulk forming process, possessing salient advantages compared with the conventional forging, including reduced force, smoothness of operation, lower investment, apt for near net shaping and producing workpieces with intricate profiles. However, the conventional rotary forging machines suffer serious limitation in their kinematics, which originates from their simple eccentric mechanism of the actuating device. The parallel-kinematics hexapod mechanism with six degrees of freedom can circumvent this limitation. The theory and practice of this concept has been successfully implemented in the present study. The inverse kinematics of hexapod has been adapted to the kinematics of the rotary forging processes. This could yield a proper method to generate the orbitally rocking motion prevailing in the process. In order to investigate the material flow in the lower die, physical modeling was carried out by the use of plasticine and several experiments were conducted in a hexapod machine. The final shapes of the workpieces, the degrees of die filling, and the forging forces were compared with the conventional forging, indicating improved results. It was observed that the motion pattern in the rotary forging influences the time and the force required for forming. The maximum forces required for rotary forging using the circular and planetary motion patterns were 32 N and 38 N respectively. In comparison, conventional forging required a significantly higher force, approximately 200 N. The time required to form a bevel gear using planetary motion was almost half of the time needed for circular motion