Production Engineering

, Volume 13, Issue 6, pp 685–692 | Cite as

Analysis of process limits for open-die forging with superimposed manipulator displacements in vertical direction

  • Martin WolfgartenEmail author
  • Niklas Reinisch
  • Gerhard Hirt
Production Process


Open-die forging is an incremental bulk metal forming process providing excellent mechanical properties and lifetime. Therefore, open-die forged parts are used for highly loaded application purposes e.g., in energy technology. However, the range of producible geometries in open-die forging is limited mainly to long and straight workpieces with simple cross-sections. Here, open-die forging with superimposed manipulator displacements offers a large potential for the production of curved workpieces. The new process concept is based on the idea, that the manipulator, originally designed as a handling device, is now actively used to control the material flow towards an intended final geometry. The idea was successfully realized for the production of curved workpieces by open-die forging. The hereby-presented investigations now aim at an analysis of the process limits for bending in vertical direction. Based on a fundamental analysis, a tilting of the samples between the forging dies and an undesired contact of the curvature with the forging die were identified as main process limits leading to a reduction of the curvature. By numerical simulation and fundamental geometric analysis, a process window was identified, where the occurrence of process limits and thus a reduction of curvature can be avoided. Finally, experimental validation was carried out at the industrially scaled open-die forging setup at IBF proving that the identified process window can successfully be realized.


Open-die forging Stress superposition Bulk metal forming Curved workpieces 



The authors would like to thank the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) for funding the project with the project-ID 256896401. Furthermore, the authors would like to thank GLAMA Maschinenbau GmbH for the excellent cooperation within the project.

Compliance with ethical standards

Conflict of interest

The authors declare that they have no conflict of interest.


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Copyright information

© German Academic Society for Production Engineering (WGP) 2019

Authors and Affiliations

  • Martin Wolfgarten
    • 1
    Email author
  • Niklas Reinisch
    • 1
  • Gerhard Hirt
    • 1
  1. 1.IBF, Institute of Metal Forming, RWTH AachenAachenGermany

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