Investigation of the required clamping force at multidirectional undercut-forging

Abstract

A hot forging process allows to produce parts of excellent quality and technical properties. Nevertheless, it is not possible to forge undercut geometries like piston pin bores, it is usually necessary to manufacture them in subsequent processes. Thus, an undercut-forging process was newly developed. Such a process requires a multidirectional forming tool, which is challenging due to a high clamping force of the tool during the process. With the research results, the requirements to the crucial tool components of heavy springs diminish, allowing using standard spring devices instead of large and expensive custom designed devices. The aim of this study is to analyze the clamping force, its origin, and influencing factors in order to facilitate the tool design. Therefore, in forming simulations the input parameters press velocity, initial temperature, and punch shape were investigated, and their effect on the clamping force was statistically evaluated. The press velocity has the major impact on the resulting clamping force. The initial part temperature and the shape of the punch tool showed minor but still significant effects. This combination of input parameters reduces the load and the stress on the tool, enabling to perform the process on smaller forging presses. Eventually, forging trials validated the results.