Process design of cold forging with thick plate for seat recliner parts

A seat recliner is a device that connects the seat back with the seat frame. It can be used to adjust the lean angle. An important component of a seat recliner is the sector tooth, which has thus far been manufactured by the fine blanking process. In this study, we propose the use of the cold-forging process as an alternative in order to achieve improved mechanical stiffness and reduced weight. To apply the cold-forging process, the entire forming process is divided into two stages in order to improve the dimensional accuracy of the tooth part of the sector tooth. Uniform plastic deformation is induced by the design of the preform on the contacting area in the sector tooth by simultaneously using a bending and a forging mechanism. By the proposed process design for the two-step cold forging process, the mechanical stiffness and surface roughness of the test product can be improved. Furthermore, the weight can be reduced by 10% by applying a 3.6-mm-thick plate instead of a 4.0-mm-thick one. Finally, the number of forming stages can be reduced without sacrificing the dimensional accuracy of the sector tooth and increasing the punch load.