Process combination of cross-wedge rolling and multi-directional forging

To determine the influence of the process combination of cross wedge rolling with multidirectional forming on the burr formation in single-cylinder crankshaft preforms, cross wedge rolling and multidirectional forming geometries were determined. For this purpose, FEM simulations were first used to narrow down the value range of the five varied parameters for subsequent experimental investigations.

The parameters were the shoulder angle, the reduction in cross-sectional area, the bearing offset, the forming speed and the workpiece temperature. After the evaluation of both investigations, there was potential for adjustments to the FEM simulations. In the course of the search for suitable parameters for adaptation, friction was identified as significant in the FEM simulations.

On the one hand, the values were varied within the friction coefficient friction factor model used; on the other hand, the suitability of another friction model, the IFUM friction model, was examined.The latter influenced the results of the FEM simulations in such a way that a sufficient approximation to the experimental investigations was achieved and a mathematical model could be formed on this basis.

cross wedge rolling, multidirectional forming, crankshaft, friction

To forge a flashless crankshaft within few steps and with low energy consumption innovative forging processes are necessary, such as cross wedge rolling and multi-directional forging. The direct combination of the two forming processes normally leads to flash at the bottom of the crankweb preform after the multi-directional forging. The reason for the flash generation is the rotation-symmetric cross wedge rolled billet, which is formed laterally to the main axis during multi-directional forging. In this paper, a parameter field in which flashless crankshaft preforms can be forged is presented. The parameters varied within the experimental research are the forming angle and the cross section area reduction at cross wedge rolling as well as the axis offset, the billet temperature and the forming velocity at the multi-directional forging. The limits of this flashless parameter field are shown in several diagrams. For a flashless combination of two forming process low values for all parameters such as a forming angle of 30°, a cross section area reduction of 30 %, and a billet temperature of 1050 °C are recommended. Furthermore, the intensity of the influence of the significant parameters are shown. The cross section area reduction thereby caused the highest range at flash generation with 0.4 mm.

multi-directional forging, cross wedge rolling, crankshaft, parameter study, flashless

A low energy demand and a fast processing time are required in each industrial process for the production of crankshafts. Crankshafts have a very complex geometry and are forged with a high percentage of flash compared to other forging parts. Recent research showed the feasibility of a flashless forging of crankshafts. One way to forge a flashless crankshaft within three steps is to use cross wedge rolling, multi-directional forging and final forging.

This paper presents the investigation results of the influence of the cross section area reduction in cross wedge rolling on different parameters at multi-directional forging. First, the state of research, the process development and tool design of cross wedge rolling and multi-directional forging are described. Then a parameter study will be presented and the influence of the cross section area reduction on flash generation, billet temperatures, forming degree, forming forces and effective strain are shown. Generally, flash generates because a rotation-symmetric billet is forced into an asymmetric movement. The influence of an increasing cross section area reduction leads to a decreasing amount of flash at the bottom of the crankwebs.

multi-directional forging, cross wedge rolling, crankshaft, parameter study, forming angle

A three step process chain with cross wedge rolling multi-directional forging and final forging would save time and money but leads to high wear at the dies. The cross wedged rolled perform can be described by forming angle and cross section area reduction. Depending on the preform geometry and the offset of the middle axis at the multi-directional forging a different amount of wear at the dies is generated. This paper shows the results of the investigation of the abrasive Archard-wear at the dies at the multi-directional forging. A short contact time, a low forming angle, ahigh cross section area reduction and a low offset of the middle axis all lead to a small depth of abrasive wear at the dies

die wear, multi-directional forging, cross wedge rolling

A low energy demand and a fast processing time are required in each industrial process for the production of crankshafts. Crankshafts have a very complex geometry and are forged with a high percentage of flash compared to other forging parts. Recent research showed the feasibility of a flashless forging of crankshafts. One way to forge a flashless crankshaft within three steps is to use cross wedge rolling, multi-directional forging and final forging.

This paper presents the investigation results of the influence of the forming angle in cross wedge rolling on different parameters at multi-directional forging. First the state of research, the process development and tool design of cross wedge rolling and multidirectional forging are described. Then the parameter study will be presented and the influence of the forming angle ? on flash generation, billet temperatures, forming degree, forming forces and effective strain are shown. Generally, flash generates because a rotation-symmetric billet is forced into an asymmetric movement. The influence of a rising forming angle leads to a higher amount of flash at the bottom of the crankwebs.

multi-directional forging, cross wedge rolling, crankshaft, parameter study, forming angle

Flashless crankshafts can be produced within four steps: cross wedge rolling, lateral extrusion, multi-directional forging and final forging. One improvement is to shorten the process by leaving out the lateral extrusion which can lead to different defects such as folds and flash. To investigate the influence of the cross wedge rolling on the multi-directional forging serval process parameters were varied. A tool concept was designed which enables a direct combination without defects and instructions for tool designing are given. The aim ist to find the process border of a parameter field in which no defects develop.

cross wedge rolling, multi-directional forging, crankshaft forging without flash

The production of a flashless crankshaft consists of four steps: cross wedge rolling, lateral extrusion, bi-directional forging and final forming. One improvement is to shorten the process by leaving out the lateral extrusion which leads to different faults as folds and flash. To investigate the influence of the cross wedge rolling on the bi-directional forging serval process parameters as forming angle and offset of the axis were varied. The purpose is to find a parameter field in which to faults occur.

cross wedge rolling, multi-directional forging, crankshaft forging without flash

Preforming is an essential step in flashless forging processes. This paper describes the development of a four stage process chain for flashless forging of a crankshaft with pin and flange. The process consists of cross wedge rolling, lateral extrusion, bi-directional forging and final forming. The finite-element-analysis (FEA) performed with the software Forge 3 and experimental tests are executed with different process parameters, like billet and tool temperature, rolling velocity and steel. To reduce process steps, like lateral extrusion, a direct combination of cross wedge rolling and bidirectional forging is analysed with FEA-software Forge 3 for a one cylinder crankshaft without pin and flange. The results of the FEA give suitable forming angles alpha for cross wedge rolling and several geometric parameters for a modification of the bi-directional tool.

cross wedge rolling, bi-directional forging, crankshaft forging without flash, preforming