Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Elektromechanisches Glattwalzen von Stahllegierungen
    ( 2019)
    Uhlmann, E.
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    Thom, S.
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    Prasol, L.
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    Haberbosch, K.
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    Drieux, S.
  • Publication
    Safety of slim tool extensions for milling operations
    ( 2019)
    Uhlmann, E.
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    Thom, S.
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    Barth, E.
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    Pache, T.
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    Prasol, L.
    The development of 5-axis machine tools (MT) allows complete machining of complex workpiece geometries. In order to counteract lacking operation space and to improve the accessibility of the workpiece, slim tool extensions (STE) are applied. Operating errors, e.g. by crash, can cause plastic deformation of STE during machining operation and therefore lead to an increased moment of inertia, and thus to rotational energy due to the spindle speed control of machine tools. Currently applied machine tool enclosures are not designed for such failures with corresponding kinetic energies EKIN. The described failure implies a risk potential for operators and a high damage potential for machine tools. In this paper, the failure scenario is identified and modeled. This includes the calculation of elastoplastic deformations of STE based on finite element analysis and analytical calculation of kinetic energies EKIN considering deformed STE. Based on the described model a parameter study is carried out considering the geometry of the STE as well as the spindle speed nS. The safety of existing machine tool enclosures is evaluated according to DIN EN 12417 in order to identify safe operating conditions. Finally, the authors suggest possible solutions addressing both, the STE and machine tool enclosure. The research presented in this paper is funded by the German Machine Tool Builders Association (VDW).
  • Publication
    Probabilities in safety of machinery - how fixed and movable guards bring about a significant risk reduction
    ( 2018)
    Mödden, H.
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    Uhlmann, E.
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    Prasol, L.
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    Thom, S.
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    Duchstein, B.
    If hazards arising from machine tools cannot be completely eliminated by design, protective devices must be provided. Separating guards prevent people from accessing or entering the danger area; in addition, they retain any parts that may have been released in the work area. An attempt shall be made here to supplement the currently purely intuitive (qualitative) consideration of the protection effects by a probabilistic scaling of the risk reduction effects. By scaling these effects, the Pareto principle can be applied: achieving the best possible benefit with minimal effort. This procedure is indispensable for machine tool manufacturers to master economic risks in global competition. Since there is no plausible risk model in current safety standards for machine safety with which risk reduction effects can be scaled, a simplified quantitative risk model is presented in this paper for this purpose (and two further papers are presented at ESREL 2018).
  • Publication
    Substitution of commercially coated tungsten carbide tools in dry cylindrical turning process by HiPIMS coated niobium carbide cutting inserts
    ( 2018)
    Uhlmann, E.
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    Hinzmann, D.
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    Kropidlowksi, K.
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    Meier, P.
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    Prasol, L.
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    Woydt, M.
    The deposition of a thin film tool coating as wear resistant layer on tungsten carbide (WC) cutting tool material marks the industrial standard for machining of various workpiece materials. Recent developments on alternative cutting materials show the potential of niobium carbide (NbC) for machining of iron-based materials and its use in cutting tool applications. In this study the tool behavior of two NbC substrates, defined as NbC0.88-12Co and NbC1.0-12Ni4Mo4VC respectively, is compared to commercial, submicron grained WC-6Co tool material. The wear performance of uncoated and physical vapor depositioned (PVD) coated cutting tools is analyzed by scanning electron microscope (SEM), electron backscatter diffraction (EBSD) and energy-dispersive x-ray spectroscopy (EDS) during adhesion tests and machining trials of carbon steel C45E. In uncoated condition, NbC1.0-12No4Mo4VC shows an average increase of material removal VW by 3% combined with a lower crater wear depth KT by 32% compared to industrial WC-6Co standard. Although microstructural defects are evident in NbC substrates, a similar tool performance of coated NbC cutting tools attests the successful substitution of WC-6Co cutting tool material for industrial machining processes.
  • Publication
  • Publication
    Increased tool performance with niobium carbide based cutting materials in dry cylindrical turning
    ( 2018)
    Uhlmann, E.
    ;
    Hinzmann, D.
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    Kropidlowksi, K.
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    Meier, P.
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    Prasol, L.
    ;
    Woydt, M.
    Niobium carbide (NbC) shows promising results as an alternative cutting tool material to tungsten carbide (WC) for turning of iron-based materials. Due to its hot hardness and low solubility of binderless NbC in solid chrome, nickel, cobalt, or iron, it presents excellent properties for cutting tool applications. These advantages result in a reduced tendency to adhesive and diffusion wear, which affects cutting tool lifetime and process stability. In order to investigate a possible substitution of the conventional substrate material tungsten carbide, the BAM Federal Institute for Materials Research and Testing and the Institute for Machine Tools and Factory Management (IWF) of the Technische Universität Berlin analyze the suitability of NbC for the use as a cutting tool in turning processes. Two different straight NbC materials are included in the machining trials prepared by Katholieke Universiteit Leuven, Belgium each differing in chemical composition and mechanical properties. A cobalt (Co) bonded niobium carbide defined as NbC0.88-12Co, a nickel (Ni) bonded NbC with the specification (NbC1.0-10TiC)-6Ni7.5VC and a commercially available cermet with a niobium content of wt.-%NbC = 25 % are selected and compared to submicron grain WC-6Co tool material. Carbon steel C45E and gear steel 42CrMo4+QT are chosen as workpiece materials of different representative technological applications for dry external cylindrical turning tests. A variation of cutting speed is carried out to show the impact of higher thermomechanical load during machining. The results evaluate the cutting performance of NbC compared to WC regarding material removal VW and crater wear KT. In contrast to WC tools NbC cutting tools show constant material removal VW at increased cutting speed vc combined with a higher process reliability.
  • Publication
    Influence of Procedure-Related Cutting Edge Micro Geometry Modification on the Production Quality When Milling Fibre Reinforced Plastics
    ( 2017)
    Uhlmann, E.
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    Stawiszynski, B.
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    Protz, F.
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    Prasol, L.
    The importance of carbon or glass fibre reinforced plastics in aviation and automotive industry has increased considerably over the last twenty years. The latest generation of commercial aircrafts for example exhibits a composite weight proportion of up to 50 %. To generate the final contour and to realize appropriate interfaces for following assembly processes, modern tools and manufacturing technologies are required to ensure high workpiece qualities. The combination of strength enhancing fibres, a ductile matrix and various laminate structures highly strains the cutting edge during the cutting process. For this field of application various cutting edge and tool geometries has been developed by several tool manufacturers to maximize wear resistant and shape accuracy. The wear mechanism and course of different cutting materials and its influence on workpiece quality during trimming of carbon and glass fibre reinforced plastics were analysed. It could be shown that an increasing tool wear does not cause necessarily low workpiece qualities. Additionally, the influence of different process parameters and strategies on the cutting edge micro geometry forming and the workpiece quality were analysed.
  • Publication
    Solutions for sustainable machining
    ( 2016)
    Uhlmann, E.
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    Peukert, B.
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    Thom, S.
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    Prasol, L.
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    Fürstmann, P.
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    Sammler, F.
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    Richarz, S.
    The manufacturing industry contributes over 19 % to the world's greenhouse gas emissions [1, 3] and 31 % of the total energy consumed annually in the United States of America [2, 3]. There is therefore an increasing demand for sustainable solutions for the production technology industry. At the TECHNISCHE UNIVERSITAET (TU) BERLIN, Germany, a collaborative research center (CRC) is focusing on new solutions for the sustainable machining of high performance alloys, with developments from machine tools frames to cutting tool technology being undertaken. An innovative machine tool concept with a modular frame, which allows a high level of flexibility, has been developed. Furthermore, add-on upgrading systems for older machine tools, which are particularly relevant for developing countries, have been developed. These systems allow the accuracy of outdated machine tools to be increased, thus making the machine tools comparable to modern systems. Finally the cutting process also requires solutions for dry machining, as the use of cooling lubricant is environmentally damaging and a significant cost contributor in machining processes. Two solutions are being developed at the TU BERLIN: an internally cooled cutting tool and a heating concept for ceramic tools to allow dry machining of high temperature alloys, for example for the aerospace industry.
  • Publication
    A novel excitation method for pyroshock simulation
    ( 2016)
    Houshmand, B.
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    Lacher, A.
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    Juengel, N.
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    Prasol, L.
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    Wagner, U. von
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    Uhlmann, E.
    Pyroshocks are structural responses to transient excitation caused by the essential use of pyrotechnic devices in aerospace applications. In order to avoid damage in aerospace structures due to pyroshocks, tests are performed on earth prior to launching space modules. In these tests, explosive loads are often replaced by alternative excitation methods such as hammer pendulums or shakers simulating on earth the impact taking place in space. However, there does not yet exist an adequate excitation method satisfying all requirements of a fast, reliable, predictable and repeatable test setup. Whereas hammers are poorely controllable in terms of generating desired shock spectra, shakers show limitations in terms of the bandwidths of up to 10 kHz which are prescribed in the test specifications. The authors present a novel contactless and non-destructive excitation method for pyroshock test devices based on a mechatronic coupling by applying Lorentz forces to the carrying structure. For generating the corresponding magnetic field, the capacitor of a Resistor-Inductor-Capacitor RLC resonator circuit is initially charged and then discharged leading to high currents in the coil which is placed close to the carrying structure. Latter is then inducing a counter current in the aluminum structure which reacts with high multidirectional Lorentz forces. Any adjustments are done by tuning the properties of the circuit such as initial charge, capacitance and inductance. By connecting several different coils, frequency modulation and by splitting the currents more complex signals can be generated matching the natural frequencies of the structure. Almost all disadvantages of common excitation methods are eliminated by the proposed mechanism.