Combined forging and punching of long pieces

Abstract

Many forged parts include piercings such as bearing surfaces. The forged pieces show a residual volume in the cross sectional area of which needs to be removed in an additional manufacturing step. By integrating this hitherto separately performed operation into the final forging step the process chain can be shortened significantly. However, up to date there is no information available on how the process parameters influence factors like dimensional accuracy, surface quality and fibre orientation in the pierced area when forming and piercing operations are combined. Therefore, a novel combined forging-/piercing- process was designed at the IPH. Trials were performed in a project with different experimental settings of the relevant process parameters like forging temperature, tool and work piece material, punch and work piece geometry. Two test parts were designed. For the first part of the project a rotation symmetric part and for the second part a part with a distinct longitudinal axis. Due to the direct correlation between residual volume thickness to be pierced and interior die pressure which determines the surface quality of the pierced area, the inserted mass is varied in the first part of the project additionally. The results of these investigations showed that the variation of the inserted mass and the forging temperature have a distinct effect on the dimensional and form accuracy of the work pieces. In contrast, the punch and work piece geometry have no effect on the form accuracy of the piercing which is shown in the results of the second project.