Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • 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.
    ;
    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
    Cutting force prediction in micro-milling considering the cutting edge micro-geometry
    ( 2019)
    Uhlmann, E.
    ;
    Polte, J.
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    Wiesner, H.M.
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    Kuche, Y.
    ;
    Polte, M.
    The micro-milling process is used for a wide range of materials and enables the manufacturing of complex geometries with micro-features. One important factor for the tool life is the cutting force Fc, which depends on the applied technology, process parameters and cutting edge micro-geometry. High cutting forces Fc can lead to tool breakage in the transition between the shank and the cutting part of cemented carbide end mills. The prediction of cutting forces Fc in micro-milling processes through cutting force models could potentially decrease the hazard of tool breakage. By including the cutting edge radius rv into the prediction model, additional correction factors can be avoided. Therefore, further knowledge about the applicability of those models for the micro-milling process with chip thickness h < 0.01 mm is needed. In this investigation, the cutting force model of KOTSCHENREUTHER [1], which takes the cutting edge radius rv into account is used for the cutting force prediction in micro-milling. In order to validate this model, an innovative lead free copper alloy CuZn21Si3P is machined. Cemented carbide micro-milling tools with tool diameter D = 1 mm were used. The manufacturing of different cutting edge radii rv was realised with the immersed tumbling process. During milling experiments with a five-axis high precision machine tool the cutting forces Fc were measured. Cutting forces in a range of 6 N < Fc < 26 N were detected. The results show good correlations between the predicted and experimental determined cutting forces Fc. Furthermore, the measured cutting edge radii rv show a high influence on the deviation of the measured and predicted cutting forces Fc.
  • Publication
    Einsatzverhalten von CVD-Diamantdünnschichtwerkzeugen
    ( 2019)
    Uhlmann, E.
    ;
    Hinzmann, D.
  • Publication
    Nachbearbeitung additiv gefertigter Titanbauteile - Potentiale des Fliehkraftgleitschleifens
    ( 2019)
    Uhlmann, E.
    ;
    Eulitz, A.
    ;
    Seiffert, K.
    ;
    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.
    ;
    Reimers, W.
    ;
    Brömmelhoff, K.
  • Publication
    Ultra-precision-milling of silicon by means of single crystal diamond tools
    ( 2019)
    Uhlmann, E.
    ;
    Polte, M.
    ;
    Rolon, D.A.
    ;
    Kühne, S.
    Silicon is an important material often employed on most of micro-electro mechanical systems (MEMS), integrated circuits, micro-chips, and micro-fluidic devices. Therefore, strategies and process parameters to machine those planar 2.5-D geometries of silicon are essential. Moreover, silicon belongs to the group of hard-brittle materials, which means that it is very likely to originate cracks during the milling operations as a result of the intermittent interaction of the cutting edge and the silicon surface. Besides, the machining of silicon results on severe tool wear. The ductile-brittle transition and tool wear reduction of the silicon-milling are aspects still not completely investigated. Consequently, this paper aims at finding the proper parameter range for ductile ultra-precision milling (UP-milling) of 2.5-D silicon geometries employing single crystal diamond cutting tools. Furthermore,the evaluation the tool wear after the process is a crucial part of the investigations. In order to fulfil such knowledge gap, single groove experiments are proposed. The milling process to generate those grooves is monitored by means of force measurements. Also, surface aspects of the machined grooves are measured through white light interferometry (WLI). For evaluating tool wear, dry UP-milling investigations are conducted and images of the cutting edges are taken by means of a scanning electron microscope (SEM). The experiments show that the machining of silicon is feasible and the ductile material removal is possible. Moreover, the process forces Fpr generated by the UP-milling process of single crystal silicon are able to be employed for monitoring and avoid the transition from ductile to brittle material removal.
  • Publication
    Micro-cutting of a MMC-composite for enhanced injection moulds
    ( 2019)
    Uhlmann, E.
    ;
    Polte, M.
    ;
    Hein, C.
    ;
    Polte, J.
    ;
    Jahnke, C.
    Tools for micro-injection moulding are currently made of hardened steel. These tools are exposed to high local loads, which significantly reduce the injection moulding tool life time tT. Furthermore, the occurring wear of the milling tool during machining of hardened steel leads to reduced surface roughness Ra and geometrical accuracy GF. Copper and aluminium alloys as mould materials provide an alternative to hardened steel with advantages regarding material removal rate QW and wear of the milling tool, but with a significantly reduced life time of the injection moulding tool tT. Until now, the combination of a good machinability and high wear resistance cannot be achieved. The approach, presented in this paper consists of an easy to machine material and the development of a wear resistant metal-matrix-composite (MMC) material layer with a hardness of up to 3,000 HV. Therefore, the pre-machined test specimens made of aluminium-bronze are coated by laser dispersing with wolfram-carbide-particles W2C-WC. Furthermore, for the finishing machining of the coated moulds, a cutting technology for the machining of W2C-WC-particles was developed. The verification of the developed technology was performed with an injection moulding process based on carbon-fibre reinforced thermoplastic material. By means of documented machining efforts, the quality indicators geometrical accuracy GF and surface roughness Ra as well as occurring tool wear, the feasibility of the developed technology was demonstrated.
  • Publication
    Mikrofräsbearbeitung von MMC-Werkstoffschichten unter Einsatz von binderlosem PKD. Analyse des Einflusses der Prozessparameter auf den Mikrofräsprozess
    ( 2019)
    Hein, C.
    ;
    Uhlmann, E.
    ;
    Polte, J.
    ;
    Wiesner, H.M.
    ;
    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