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B2 - Micro Elements

Machining of Molds with Filigree Structures for Sheet-Bulk Metal Forming

Project Status: finished

Last Update: 02.10.2020


Manufacturing the forming tools required by SBMF represents an enormous challenge for the micromilling processes used in this task. Especially the mechanisms of hard machining have not yet been examined in detail to manufacture filigree structures from materials of high hardness. The latter and the five-axis machining process, which is required due to technological and efficiency reasons, demand fundamental knowledge of the process. This knowledge is attained in this subproject B2 to achieve a reliable and efficient control of the micromilling process and to manufacture suitable and highly precise complex dies having filigree structures for SBMF. Therefore, the milling of parts having high aspect ratios in combination with the material properties, especially the high hardness, is analysed for a cold-working steel (1.2379), powder and smelted metallurgical produced high-speed steel (1.3344 and 1.3343) with a hardness > 60 HRC. Process parameters and machining strategies are developed, which allow the milling of dies with filigree structures at the same quality level as it is achievable for macroscopic dies nowadays. Further, the SBMF tools require a design which supports the form filling for the secondary form elements. This can be achieved by a material flow control, based on a tool-sided structuring of the surface by micromilling.

The milling of the geometrically complex, filigree secondary elements of the dies demands, among other things, the manufacturing of toothings with radii of R < 0.2 mm by small micromilling tools of d ≤ 1 mm. The application of these small tools and the resulting downscaling of the milling process from the macro to the micro range requires a comprehensive adaptation of the machining process. Especially the strong tool wear and the high tool deflection can have a stronger influence on the process reliability and process accuracy than it is commonly known from the macro range.

In milling processes with small tool diameters, the tool deflection and the resulting dimensional deviations are an important issue as well. Because of their low stiffness, the tools show a low resistance to the applied torques and forces. Especially for the machining of the hard materials described above, up to six times higher cutting forces are expected in comparison to micromilling of titanium alloys or stainless steels, resulting in large deflections. In this context, the magnitude of the tool deflection has to be determined for the machining of simple structures and for five-axis machining of geometries that are more complex as well. In a subsequent step, these investigations are extended to the machining of free-formed surfaces. To produce filigree structures with high aspect ratios, five-axis micromilling strategies, which have not been studied extensively so far, are used. The dynamic properties of the appropriate five-axis machine tool are very important with regard to the overall machining quality. For instance, the rotational axes of the machine tools feature a lower accuracy than the linear axes. Furthermore, because of their low motion speed and acceleration capabilities, the rotational axes are often not able to meet the programmed feed rates. For this reason, five-axis milling strategies, which take into account these inadequacies, are developed in this project. 

B2 also focuses on the development and production of surface structures. Their design is based on the kinematics of micromilling (technological structures) and on bionically-inspired structures. For the manufacturing process, influencing variables have to be analysed and suitable process boundary conditions must be defined. Due to the high number of microstructural elements on surfaces of just a few millimetres in size, the calculation of NC paths within the common CAD/CAM process chain is no longer effective (> 6,000 structure elements). Therefore, new repetitive approaches to generate machining programmes are developed. Furthermore, a simulation-based process design is developed in order to achieve a higher degree of applicability.

Working Groups



    • Meijer, A.; Biermann, D.: Machining of Molds with Filigree Structures for Sheet-Bulk Metal Forming. In: M. Merklein, A.E. Tekkaya, B.-A. Behrens (Edt.): Sheet Bulk Metal Forming - Research Results of the TCRC73, (2021), Springer Nature Switzerland AG, pp. 141-171


    • Weikert, T.; Tremmel, S.; Stangier, D.; Tillmann, W.; Krebs, E.; Biermann, D.: Tribological Studies on Multi-Coated Forming Tools. In: Journal of Manufacturing Processes, 49(2020), pp. 141-152
    • Behrens, B.; Meijer, A.; Stangier, D.; Hübner, S.; Biermann, D.; Tillmann, W.; Rosenbusch, D.; , .: Static and oscillation superimposed ring compression tests with structured and coated tools for Sheet-Bulk Metal Forming. In: Journal of Manufacturing Processes, 55(2020), pp. 78-86
    • Platt, T.; Meijer, A.; Biermann, D.: Conduction-Based Thermally Assisted Micromilling Process for Cutting Difficult-to-Machine Materials. In: Journal of Manufacturing and Materials Processing (Edt.): Advanced Manufacturing and Machining Processes, 4(2020)2, pp. 34


    • Behrens, B.; Biermann, D.; Tillmann, W.; Krimm, R.; Meijer, A.; Schewe, M.; Stangier, D.; Commichau, O.; Müller, P.; Rosenbusch, D.; Menzel, A.: Untersuchungen strukturierter Werkzeugflächen und der Einfluss auf den Werkzeugverschleiß. In: 4. Industriekolloquium Blechmassivumformung 2019 – DFG Transregio 73, (2019), pp. 7-30
    • , .; Bergmann, J. A. ; Krebs, E.; Biermann, D.; Wiederkehr, P.: Analytical and Simulation-Based Prediction of Surface Roughness for Micromilling Hardened HSS . In: J. Manuf. Mater. Process, 3(2019)3, pp. 1-17
    • Pulvermetallurgie der Hartmetalle - Schlüsseltechnologie für die spanende Fertigung und ihre Anwendungsgebiete. In: Danninger, H.; Sigl, L.; Broeckmann, C. (Edt.): Pulvermetallurgie- Schlüsseltechnologie für innovative Systemlösungen, 35(2019)1, Heimdall Verlag, pp. 3-27
    • Biermann, D.; , .; Michel, S.: Optimierung zerspanender Prozesse in kleinsten Dimensionen. In: maschinenbau - Das Schweizer Industriemagazin, 5(2019)1, pp. 18,21
    • Baumann, J.; Krebs, E.; Biermann, D.: Chatter avoidance in milling by using advanced cutting tools with structured functional surfaces. In: Modern Machining Science Journal, 1(2019)1, pp. 3019-3026


    • Krebs, E.; Wolf, M.; Biermann, D.; Tillmann, W.; Stangier, D.: High-quality cutting edge preparation of micromilling tools using wet abrasive jet machining process. In: Production Engineering, 12(2018), pp. 45-51
    • Meijer, A.; Krebs, E.; Wiederkehr, P.; Biermann, D.: Prediction of Feed-Rate Slowdowns in Precise Micromilling Processes. In: J. Manuf. Mater. Process, 2(2018)1, MPDI, pp. 1-14
    • Keitzel, G.; , .: Kräfte messen - Prozesse optimieren. In: Mikroproduktion, 4(2018)1, MIKROvent, pp. 40-44
    • Biermann, D.; , .; Ott: Präparation von Mikrofräswerkzeugen aus Vollhartmetall mit elastisch gebundenen Schleifkörpern. In: Jahrbuch Schleifen, Honen, Läppen und Polieren: Verfahren und Maschinen, 68(2018)1, Vulkan Verlag GmbH, pp. 80-98
    • Biermann, D.; , .; Krebs, E.; Michel, S.; Jaeger, J.: Neue Entwicklungen für den produktiven Einsatz von Hartmetallwerkzeugen in kleinsten Dimensionen. In: Danninger, H.; Sigl, L.; Broeckmann, C. (Edt.): Pulvermetallurgie - neue Herausforderungen und neue Wege, 34(2018)1, Heimdall Verlag, pp. 135-155


    • Sieczkarek, P.; Wernicke, S.; Gies, S.; Tekkaya, A.; Krebs, E.; Wiederkehr, P.; Biermann, D.; Tillmann, W.; Stangier, D.: Improvement strategies for the formfilling in incremental gear forming processes. In: Production Engineering – Research and Development, 11(2017), Springer, pp. 623-631
    • Tillmann, W.; Stangier, D.; Lopes-Dias, N.-F.; Biermann, D.; Krebs, E.: Adjustment of Friction by Duplex-Treated, Bionic Structures for Sheet-Bulk Metal Forming. In: Tribology International, 111(2017), pp. 9-17
    • Krebs, E.: Simulationsgestützte Mikrofräsbearbeitung gehärteter Werkzeugstähle zur Herstellung filigraner Formelemente und funktionaler Oberflächenstrukturen. In: Prof. Dr.-Ing. Prof. h.c. Dirk Biermann (Edt.): Dissertation Krebs, E., 1(2017)1, Essen: Vulkan Verlag GmbH, published



      • 15.05.2019: , .: Mikrozerspanung gehärteter Schnellarbeitsstähle , 11. Tooling Konferenz, Aachen


      • 08.02.2018: Krebs, E.: Simulationsgestützte Prozessanalyse und –vorhersage bei der Mikrofräsbearbeitung, Dortmund
      • 24.08.2018: , .: Mikrobearbeitung - Von der Simulation des Materialabtrages bis zur intelligenten Fabrik , Sino Summer School, ISF, Dortmund
      • 28.09.2018: Wiederkehr, P.: Mikrobearbeitung bionischer Oberflächenstrukturen zur tribologischen Optimierung von Umfromprozessen, 2. Sino Symposium, Bochum
      • 15.11.2018: Biermann, D.: Neue Entwicklungen für den produktiven Einsatz von Hartmetallwerkzeugen in kleinsten Dimensionen, Hagener Symposium, Fachverband für Pulvermetallurgie, Hagen
      • 28.11.2018: , .: Prozessauslegung zur Strukturierung von Freiformflächen durch Replikation und Verzerrung von Sektionen eines NC Programmes, Euspen - SIG: Structured & Freeform Surfaces, Paris