Deformation mechanism of forging tool for multi-stage forming of deep groove ball bearing

In this study, two design configurations routinely adopted in actual mass production for deep groove ball bearing rings of multi-stage warm forging process are investigated numerically and experimentally. The deformation mechanism, forging defects, microstructures, and compositions analysis are the main focus of this study. For type A design with a stepped configuration, inner and outer rings are automatically pierced and separated in the multi-step forging machine. On the other hand, for the type B geometry, additional step is required by the customized milling machine. For type A design, the main issue encountered during actual forging process is the inadequate material filling at the upper corner radius and folding defects at the transition area of inner wall of forgings. For type B design, the material flow is unsatisfactorily directed and lower outer radius is insufficiently filled. Therefore, variations of forging parameters include billet weight, punch/knock out pin geometry and the effect of lubricating fluid is systematically investigated. In addition, the finite element method has been performed and compared with the actual forging experiments. In summary, the modification of tooling design, dimension variation of billet weight, and the forging temperature difference as impacted by the lubricating fluid, which are identified as the three major factors of the forging integrity and stability of the mass production process. The results are particularly useful for the advanced tooling design and contribute largely to minimize the tool failure and the integrity of the bearing forged.