When producing racks by cold rotary forging, the top punch and the rack teeth definitely intervene and thus the top punch has to be amended, which makes the technical designing processes difficult and complex (Han et al., 2016, “Cold Orbital Forging of Gear Rack,” Int. J. Mech. Sci., 117(10), pp. 227–242). In this study, a novel cold rotary forging method of producing racks is put forward to avoid the interventions between the top punch and the racks. Thus, the top punch need not be amended and the technical designing processes correspondingly become simple. In light of this presented method, a novel idea for cold rotary forging of producing multiple racks using one set of punch is motivated. The concrete researches are as follows: First, the mathematical models are developed and three kinds of key forging conditions in cold rotary forging of racks are calculated to avoid the interventions between the top punch and the racks. The first one is the condition that the top punch and the rack teeth do not intervene. The second one is the condition that the top punch and cylindrical surfaces of racks do not intervene. The third one is the condition that the top punch can be successfully constructed. On the basis of these three kinds of key forging conditions, the workpiece is optimized and the cold rotary forging processes of racks with constant and variable transmission ratio are examined using finite element (FE) simulations. The experimental researches are also conducted. The results show that for both racks with constant and variable transmission ratio, the obtained key forging conditions are effective and the presented cold rotary forging principles of producing multiple racks using one set of punch are feasible.
