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Experimental investigation of a variable flash gap regarding material flow and influence of trigger forces

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Abstract

Closed die forging with flash is the most common method of bulk forming processes. One main property of these processes is the use of a surplus material to ensure a complete filling of the cavity of the forging die. The surplus material is driven out of the die through the flash land. The design of the flash land has a major influence on the filling of the die. Usually, the dimensions of the flash land are fixed during the manufacturing of the die and can’t be changed within the forging process. Additional machining operations are necessary to adapt to e.g. different process parameters or to occurring die wear which deteriorates the filling of the cavity. By use of a variable and moveable flash gap which can be actively changed during the forging process more material can be held in the cavity, thus permitting the improvement of the filling of the cavity. Additionally, such a system can be used to adapt to varying process parameters within the process. In this paper the investigation of a variable flash gap will be described. The influence of such a system on the filling of the die cavity is determined. This is done by comparison with a conventional forging process with a fixed flash land. Additionally, different trigger forces of the variable flash gap were investigated which also have an influence on the material flow during the forming operation. At last, the results of experimental trials are compared to results of FEA simulations. Experimental trials showed that the variable flash gap has a clear influence on the material flow. The higher the flash ratio, the bigger is the influence of the variable flash gap. Differences in height of the parts of 4.6 mm, which correspond to 17.2 %, were reached between a conventionally forged part and a part forged with a variable flash gap. Different trigger forces also have an influence on the height of the parts. The higher the trigger force, the bigger the influence of the variable flash gap. In general, the results match the predictions of FEA simulations. Experimental trials showed that a variable flash gap is able to improve the filling of the cavity. This method can be used to increase the quality of forging parts by a much easier adaption to different process parameters without additional machining operations.

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Acknowledgments

The research project “Mechanismen zur Steuerung einer variablen Gratbahn und deren Einfluss auf die verschleiß- und volumenschwankungsabhängige Formfüllung beim Gesenkschmieden” (DFG NI 1187/12-1) was funded by the German Research Foundation (Deutsche Forschungsgemeinschaft—DFG). The authors thank the DFG for its support.

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The authors declare that they have no conflict of interest.

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Authors and Affiliations

  1. Institut für Integrierte Produktion Hannover (IPH), Hollerithallee 6, 30419, Hannover, Germany

    Jan Langner, Malte Stonis & Bernd-Arno Behrens

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  1. Jan Langner
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  2. Malte Stonis
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  3. Bernd-Arno Behrens
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Correspondence to Jan Langner.

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Langner, J., Stonis, M. & Behrens, BA. Experimental investigation of a variable flash gap regarding material flow and influence of trigger forces. Prod. Eng. Res. Devel. 9, 289–297 (2015). https://doi.org/10.1007/s11740-015-0611-1

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  • DOI: https://doi.org/10.1007/s11740-015-0611-1

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