【正文】 one single stageto be pletely formed from a raw material slug [5,6].For the precision forging of a connecting rod a tool isdesigned in which the preformed and upset slug is inserted inthe die cavity, thereafter the tool is closed and the puncheswhich are included in the die form the material to the finaldesign (Fig. 2).Besides the special requirements concerning the actualdesign of precision forged products, very exact masses of theraw parts with deviations less than % are prerequisites fora successful process. The temperatures of the billets and diesneed to be controlled carefully to facilitate a temperaturedeviation of less than 20 8C. Additionally the materialhandling and forming of the workpiece needs to be performed with a high degree of precision. For this a press andother manufacturing ponents with very small tolerancesregarding geometric deviations are needed.As mentioned above, precision forging processes havecertain special requirements concerning the design of theproduct and as a result to the forging die.For the described research project a conventionally forgedconnecting rod needed to be adapted for the production witha precision forging process. As mentioned above precisionforging is performed without flash (Fig. 3).Fig. 1. Integrated ITsystems and organization.Fig. 2. Precision forging of connecting rod.Fig. 3. Precision forged connecting rod.S. Reinsch et al. / Journal of Materials Processing Technology 138 (2020) 16–21 17The technology of closed die forging is used with stampsin the eyes and the shaft doing the forming work. To enablethe connecting rod to be forged in that way some changes inthe conventional forging geometry have to be made. In Fig. 4the changes in the area of the shaft are shown.First it is important that the transition between the weband the wad is not smooth like for conventional forging butwith a revolving edge and a vertical side face. This isnecessary to allow the stamp to perate the materialwithout any collision with the die sinking and to avoid anoffset due to deviations in the path of the stamp (Fig. 4).As the mass exactness of the inserted part is only in arange of 1% the area of the stamps is necessary to pensate the mass deviation. This is the reason for thedeviation of the stamp path. The revolving edge is a promise between a smooth transition and an acceptable loadof the die sinking. With FEMsimulation the angle has beenoptimized to . 5 shows the occurring stress for a608 angle is not inflicting the die sinking and therefore thetool life quantity.Additional changes have to be made in the area betweenthe eyes and the shaft. The reasons are the displacement ofthe material between the stamps and the load of the diesinking as mentioned above (Fig. 6).An important requirement for the development of a precision forgeable geometry is that the mass and the stresses ofFig. 4. Design change for precision forging of the shaft crosssection.Fig. 5. FEMsimulation of tool angle. Fig. 6. CAD drawing of connect rod.18 S. Reinsch et al. / Journal of Materials Processing Technology 138 (2020) 16–21the product have to be the same as for the original design.This can be verified by FEMsimulation during the development process.Since the precision forged products are forged withoutflash, the material flow needs to be examined carefully todesign the die according to that specific requirement. Nevertheless the die needs to be filled out plete as well toguarantee the anticipated mechanical specification. For thisreason finite element simulation is utilized to identify specialareas of concern where the design of the sequence needs tobe modified.Precision forging tools have to fulfil special specificationsconcerning the tolerances that have to be kept for the forgingprocess. Hereby especially the precision that can beachieved for the tool production is significant.Moreover the wear of the tool needs to be reduced to aminimum possible value, since the degree of wear is essential for the precision that can be achieved. The time betweenmaintenance of the tool can be increased significantly byreducing friction between product and die.Another significant issue for reducing the friction andtherefore minimizing tear and wear is the permanent monitoring and control of the process parameters that arerelevant for the product quality. A closed loop processcontrol of die and product temperature and forces enablesa documentation and online statistical analysis for instantfeedback not only concerning the tool wear, but the information is essential for production management system aswell.3. Process design for precision forgingNot only the product and tool need to fulfil enhancedspecifications due to the higher degree of precision. Theprocess needs to meet the requirements to be flexible, quickand efficient. As mentioned above.To reach a flexible, quick but stable precision forgingprocess, attention has to be paid to the sensitivity of theforging process. One issue already mentioned above is theprecision and temperature exactness of the tool and product.Another important issue is the flexibility and accuracy of thematerial handling gear especially for the