Lehrstuhl für Fertigungstechnologie, Universität Erlangen-Nürnberg

Tool life estimation of cold forging tools



Datum: 08.02.2006


Author

  • Dr.-Ing. Markus Meidert

Reporter

  • Prof. Dr.-Ing. Dr.-Ing. E.h. mult. Dr.h.c. M. Geiger
  • Prof. Dr.-Ing. Dr.-Ing. E.h. R. Geiger
  • Prof. Dr.-Ing. habil. G. Kuhn

Tools for cold forging are subjected to extreme cyclic loads by the forming process. They very often fail by developing cracks due to material deterioration caused by low-cycle fatigue. The tool costs can reach a significant portion of the total production costs and straightforward methods for optimization of tool service life are of high economical interest. However, optimization of service life by tool design can be very tedious because it is in many cases still done by trial and error and highly depends on the experience of the designer. Tool life can be enhanced by altering several parameters such as the prestressing of the die, stiffness of the tool assembly and the die geometry itself.For a straightforward tool design a concept for tool life estimation by an energetic damage parameter was further developed. The basis was test data of high strength PM tool steels obtained in static and cyclic material tests.The verification of the numerical tool life estimation was done by taking complex cold forging tools as representative examples. It was possible to show that a straightforward tool design with realistic lifetime estimation can be done and corresponds well with actual lifetimes observed in industrial production. The location of failure was predicted correctly. The damage calculation and tool life prediction was fully integrated into an existing FEM environment, an important aspect for their applicability and acceptance in industrial tool design.