Now showing 1 - 10 of 293
  • Publication
    Effects on the distortion of Inconel 718 components along a hybrid laser-based additive manufacturing process chain using laser powder bed fusion and laser metal deposition
    ( 2021)
    Uhlmann, E.
    ;
    Düchting, J.
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    Petrat, T.
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    Krohmer, E.
    ;
    Graf, B.
    ;
    Rethmeier, M.
    The combination of laser powder bed fusion (LPBF), known for its geometrical freedom and accuracy, and the nozzle-based laser metal deposition process (LMD), known for its high build-up rates, has great potential to reduce the additive manufacturing times for large metallic parts. For the industrial application of the LPBF-LMD hybrid process chain, it is necessary to investigate the influence of the LMD process on the LPBF substrate. In addition, the build plate material also has a significant impact on the occurrence of distortion along the additive manufacturing process chain. In the literature, steel build plates are often used in laser-based additive manufacturing processes of Inconel 718, since a good metallurgical bonding can be assured whilst reducing costs in the production and restoration of the build plates. This paper examines the distortion caused by LMD material deposition and the influence of the build plate material along the hybrid additive manufacturing process chain. Twin cantilevers are manufactured by LPBF and an additional layer is subsequently deposited with LMD. The distortion is measured in the as-built condition as well as after heat treatment. The effect of different LMD hatch strategies on the distortion is determined. The experiments are conducted using the nickel-base alloy Inconel 718. The results show a significant influence of LMD path strategies on distortion, with shorter tool paths leading to less distortion. The remaining distortion after heat treatment is considerably dependent on the material of the build plate.
  • Publication
    Niobcarbid statt Wolframcarbid Alternativer Schneidstoff in der Drehbearbeitung
    ( 2019)
    Kropidlowski, K.
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    Uhlmann, E.
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    Woydt, M.
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    Theiler, G.
    ;
    Gradt, T.
  • Publication
    3-Achs-Portalfräsmaschine als Demonstrator für ein modulares Werkzeugmaschinengestell
    ( 2019)
    Uhlmann, E.
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    Polte, M.
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    Blumberg, J.
    ;
    Peukert, B.
  • Publication
    Increasing the productivity and quality of flute grinding processes through the use of layered grinding wheels
    ( 2019)
    Uhlmann, E.
    ;
    Schroer, N.
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    Muthulingam, A.
    ;
    Gulzow, B.
    Due to the increasing relevance of resource efficiency, the production of cutting tools is exposed to increasing demands in regard to productivity and quality. Flute grinding is of particular significance within the various grinding operations used in tool manufacturing. Apart from the rake face, the flute grinding process determines the quality of the cutting edges. However, the grinding wheels typically used for flute grinding are not designed to take the complex contact conditions of this process into account. This paper presents a method for designing application-oriented grinding wheels to improve the productivity and the quality of grinding processes. Firstly, a model is presented which is used to simulate the contact conditions. The results show the significance of the grinding wheel edge in flute grinding. Based on that, grinding wheels with different layers over its width were developed to compensate the varying and complex contact conditions. To verify this approach technological experiments were carried out.
  • Publication
    Einsatzverhalten von CVD-Diamantdünnschichtwerkzeugen
    ( 2019)
    Uhlmann, E.
    ;
    Hinzmann, D.
  • Publication
    Nachbearbeitung additiv gefertigter Titanbauteile - Potentiale des Fliehkraftgleitschleifens
    ( 2019)
    Uhlmann, E.
    ;
    Eulitz, A.
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    Seiffert, K.
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    Kersting, R.
    ;
    Schenk, S.
    Additive manufactured parts can be post-processed by centrifugal disc finishing as bulk. The choice of suitable media is of high importance for economic post-processing. In this paper, topography and shape changes of machined workpieces are investigated and a multistage process for post-processing additive manufactured Titanium parts is developed.
  • Publication
    Hochleistungsbohrwerkzeuge für CFK
    ( 2019)
    Uhlmann, E.
    ;
    Christiansen, G.
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    Reimers, W.
    ;
    Brömmelhoff, K.
  • Publication
    Application of niobium carbide based cutting materials for peripheral milling of CFRP
    ( 2019)
    Uhlmann, E.
    ;
    Meier, P.
    ;
    Hinzmann, D.
    Due to its inherent material properties, the implementation of niobium carbide (NbC) as hard phase in cutting materials represents a promising alternative to machining. Recent investigations show equivalent tool life in metal cutting compared with cemented carbides based on tungsten carbide (WC). Besides metal cutting, the machining of high-performance composite materials poses an increasing importance due to its growing demand in the automotive and aeronautical sector. NbC and its wear resistance against abrasion can be suitable for this specific application. Additionally, the low density of NbC indicates an advantageous dynamic behaviour. Thus, this study focuses on the milling of carbon fiber reinforced plastics (CFRP). Complex tool geometries are implemented in a peripheral milling strategy. The machining trials are conducted with uncoated NbC-based cutting materials in CFRP with varying cutting speeds vc. The utilized NbC compositions (NbC-10TiC)-6Ni7.5VC and (NbC-15TiC7N3)-5Ni7.5WC2.5Mo2C embedded in a Nickel (Ni) matrix were applied and compared towards their performance with an industrial available cemented carbide (WC-Co). As tool life criteria, a tool diameter reduction of Dd = 0.1 mm and a cutting path of lc = 10.000 mm were defined. Apart from tool life performance, the workpiece quality was assessed. An inferior performance was identified with (NbC-10TiC)-6Ni7.5VC in terms of tool life compared to WC-Co, which can be attributed to microstructure issues. Yet, (NbC-15TiC7N3)-5Ni7.5WC2.5Mo2C shows a competitive performance in machining with an achieved cutting path lc identical to WC-Co. It can be stated, that NbC-Ni systems can accomplish an equivalent performance in comparison to WC-Co when machining CFRP.
  • Publication
    Mikrofräsbearbeitung von MMC-Werkstoffschichten unter Einsatz von binderlosem PKD. Analyse des Einflusses der Prozessparameter auf den Mikrofräsprozess
    ( 2019)
    Hein, C.
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    Uhlmann, E.
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    Polte, J.
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    Wiesner, H.M.
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    Jahnke, C.
    ;
    Polte, M.
    Micro-injection moulding is a key technology for the cost-effective production of plastic parts. The commonly used moulds are made of hardened steel and machined by micro-milling with coated cemented carbide tools. Today, these tools suffer from random tool breakage and excessive wear. One solution of this problem is to produce injection moulds made of non-ferrous metals and enhance them by applying a tungsten carbide matrix on the surface. Thus, this investigation addresses the micro-milling process of the resulting Metal-Matrix-Composites. Furthermore, the feasibility of binderless polycrystalline diamond as an innovative cutting material could be shown for this purpose