Defects like folds can arise using forging for the production of long flat pieces made of aluminium. A special defect is the formation of inner folds. These can be seen in the grain flow. Inner folds have a negative effect on the dynamic properties of the forged part. As a production process, forging can be divided into single-directional and multi-directional forging. The formation of inner folds was observed at the single-directional forging. By using the multi-directional forging, a forming operation working from different directions, the forming can be set variably. Thus the development of folds can be prevented. A newly developed method can help in the selection of the forming process and in determining an appropriate tool geometry. Here especially the area is adapted, where the development of inner folds occur. Therefore a calculation model was developed. It integrates a computer-aided identification of the inner folds. Using this model, a correction of the parametrically constructed forging tool is possible.
multidirectional-forging, long flat pieces, aluminium, fibre orientation
Multi-directional forging enables flashless preforming for complex workpiece geometries by a cross-section formation and mass distribution in one forging stroke of the press. The process principle is based on a tool with multi-directional acting forming punches. In addition to the vertical forming by a punch a horizontal deformation is performed by horizontally arranged sliders. The drive of the sliders is performed by a redirection of the ram movement using wedges. The multi-directional forging has been studied and developed further over the past decade in a number of research projects. Starting with simple flashless, flat preforms for connecting rods made of steel, the technical feasibility of this method has been demonstrated. In subsequent steps, the principle has been transferred to crankshafts. As part of the Collaborative Research Centre 489, the crankshaft was broken down to a unit cell in order to investigate the fundamental transformation of the bearings and the crank webs. With this knowledge, forging sequences for simplified single and two-cylinder crankshafts were designed (without secondary form elements). Currently the forging sequence for a full two-cylinder crankshaft is designed with secondary design elements. The interaction of the mass distribution by cross-wedge rolling and multi-directional forging is analyzed. The flashless forging of two-cylinder crankshafts with such complicated geometries and corresponding necessary material flow is only possible using a multidirectional preforming. Finally, the applicability of the method to aluminum was investigated in the context of a DFG project – again based on a flat part long preforms. Here particularly clearly the limits of the process could be shown. Various forming directions were combined. With some of these combinations flash developed during the forming operation. Others have shown to be usable for a flashless preforming of complicated geometries.
multidirectional forging, flashless, preforming, cross-wedge rolling, connecting rod, crankshaft, st
To overcome the geometrical limitation of warm forging, in the European research project "DeVaPro - Development of a Variable warm forging Process chain" new rolling and forging processes are developed. The aim of the project is to develop a warm forging process chain by selecting the best suitable hot preforming technology to obtain the desired mass distribution before warm forging. The technology will be adapted to the specific requirements of warm forming. A warm rolling operation and an induction reheating process will be introduced within this project. A steering link and a connecting rod are used as sample parts.
warm forging, process chain, cross wedge rolling
