Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Micro-texture dependent temperature distribution of CVD diamond thick film cutting tools during turning of Ti-6Al-4V
    ( 2022)
    Uhlmann, Eckart
    ;
    Schröter, D.
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    Gärtner, Eric
    Machining titanium alloys such as Ti-6Al-4V results in a high thermomechanical load on cutting tools and consequently short tool lifes. With respect to a necessary reduction of the resulting cutting tool temperatures, ultrashort pulse (USP) laser fabricated micro-textured rake faces offer direct supply of cooling lubricant into the cutting zone and lead to a reduced heat induction. As a result, micro-textured CVD diamond thick film cutting tools are also capable of machining high-performance materials due to reduced contact temperatures. In the scope of the research, the resulting temperature distribution for micro-textured rake faces will be compared under both dry and wet process conditions. Measurements show a reduction of the resulting cutting tool temperatures of Δϑt = 27.9 % using micro-textured cutting tools compared to non-textured cutting tools. A validated simulation provides valuable information about the contact temperatures enabling a specific development of the micro-texture geometry. As a result, a reduction of the contact temperature between chip and rake face by ΔϑT = 24.7 % was possible.
  • Publication
    Simulativer Vergleich tubularer Peltierelemente
    ( 2022)
    Binninger, Roland
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    Pernau, Hans-Fridtjof
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    Schäfer-Welsen, Olaf
    ;
    Triebel, Florian
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    Polte, Mitchel
    ;
    Uhlmann, Eckart
    Der Einsatz von Peltierelementen bietet in der Temperierung von Prozessen und Bauteilen einen großen Vorteil gegenüber der in technischen Anwendungen üblicherweise eingesetzten Fluidkühlung. Sie pumpen Wärme rein elektrisch und stellen Temperaturen sehr schnell sowie präzise ein. Für eine neuartige, thermoelektrisch temperierte Motorspindel wurden in Kooperation zwischen dem Fraunhofer-Institut für Physikalische Messtechnik IPM und dem Institut für Werkzeugmaschinen und Fabrikbetrieb IWF der Technischen Universität Berlin zwei unterschiedliche Ansätze tubularer Peltierelemente simulativ verglichen. Die Ergebnisse zeigen, dass es mit beiden Konzepten möglich ist, induzierte Wärmeströme am Lagersitz abzu­führen, um diesen auf eine vorgegebene Temperatur zu regeln.
  • Publication
    Wolframschmelzcarbidbasierte MMC-Schichten für den industriellen Einsatz im Formenbau
    ( 2022)
    Langebeck, Anika
    ;
    Jahnke, Christian
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    Wünderlich, Tim
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    Hein, Christoph
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    Bohlen, Annika
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    Uhlmann, Eckart
    Zur Steigerung der abrasiven Verschleißbeständigkeit können Oberflächen lokal mit Hartpartikeln verstärkt werden. Diese sogenannten Metal-Matrix-Composit(MMC)-Schichten können mittels Laserstrahldispergieren gefertigt und durch Mikrofräsen nachbearbeitet werden. Im hier vorgestellten Forschungsvorhaben wurde als Grundwerkstoff verwendete Aluminiumbronze (CuAl10Ni5Fe4) mit Wolframschmelzcarbid verstärkt. Der Hartpartikelgehalt kann dabei durch eine Steigerung des Pulvermassenstroms bis zur Packungsdichte des unverarbeiteten Pulvers erhöht werden. Über eine temperaturbasierte Leistungsregelung kann eine gleichbleibend homogene MMC-Schicht mit konstanter Dicke und Tiefe dispergiert werden. Durch das Mikrofräsen mit optimierten Parametern können qualitativ hochwertige MMC-Oberflächen für den industriellen Einsatz in Spritzgusswerkzeugen hergestellt werden. Dabei wurde vor allem der Zahnvorschub fz als kritischer Prozessparameter identifiziert.
  • Publication
    Harmonization of Heterogeneous Asset Administration Shells
    ( 2022)
    Koutrakis, Nikolaos-Stefanos
    ;
    Gowtham, Varun
    ;
    Pilchau, W.B.P. von
    ;
    Jung, T.J.
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    Polte, Julian
    ;
    Hähner, J.
    ;
    Corici, Marius-Iulian
    ;
    Magedanz, Thomas
    ;
    Uhlmann, Eckart
    In the era of digital transformation of the manufacturing and process industry, heterogeneity of assets is one of the most challenging issues towards digitally integrating components within the Industrial Internet of Things. In this context every participant relies on its proprietary digitalization approach envisioned by Plattform Industrie 4.0. To consolidate these heterogeneous data exchange interfaces, e.g communication protocols, data formats etc., an intermediate step of harmonization is required. Our contribution provides an architecture based on the Asset Administration Shell standard to bring heterogeneous Cyber-Physical-Systems together. We illustrate the functionality through an abstract use-case.
  • Publication
    Sharpening mechanism of extremely sharp edges for diamond micro mills
    ( 2022)
    Wu, Y.
    ;
    He, N.
    ;
    Chen, N.
    ;
    Polte, Julian
    ;
    Yan, B.
    ;
    Li, L.
    ;
    Uhlmann, Eckart
    The fabrication of extremely sharp cutting edges for ultra-hard micro mills is crucial for suppressing the severe size effect, restraining burr formation, and improving the surface quality of widely used micro components in micro milling. In this study, a hybrid machining technique, laser-assisted precision grinding, is proposed to improve the grinding efficiency and increase the sharpness of the cutting edges of polycrystalline diamond (PCD) micro end mills. A transient heat model of laser ablation was constructed to investigate the laser-cutting mechanism of PCD with a cobalt binder. Facilitated by suitable heat conduction, cobalt absorbs photon energy to heat itself and transmits thermal energy to the surrounding diamond, resulting in uniform graphitisation and cobalt oxidation on the cut section. Hence, the affected layer on the cut section can be easily ground using a low grinding load. Moreover, the subsequent grinding mechanism of the laser-cut section was demonstrated. The diamond was removed via micro-abrasion without any intercrystalline cracks or grain dislodgement, and the abrasive grain size was optimised to achieve superior ground surface quality. Thus, the uniform graphitization, micro abrasion, and smaller material stress near edge contributed to the extremely sharp edges. Furthermore, PCD micro end mills with a diameter of 400 μm, aspect ratio of 2, and cutting-edge radius of approximately 0.2 μm were fabricated, showing a superior sharpness compared with that of the end mills with an edge radius of 1-5 μm reported hitherto. Subsequently, micro-milling experiments were conducted on oxygen-free high-conductivity copper (OFHC) using the self-fabricated PCD micro end mills. Almost no burrs were observed, and the surface roughness of the machined groove was 19.8 nm, indicating the superior cutting performance of the fabricated PCD micro end mills.
  • Publication
    Gear Wheel Finishing with Abrasive Brushing Tools to Improve the Surface Quality of Tooth Flanks for the Industrial Application
    ( 2022)
    Gülzow, Bernhard
    ;
    Uhlmann, Eckart
    A high surface quality of tooth flanks can improve the service life and the performance of gears, as well as reduce acoustic emissions. However, high demands on the gear geometry pose a challenge for the finishing of tooth flank surfaces because the dimensional accuracy that can be achieved with modern grinding processes must not be impaired by the finishing process. A preceding study has shown fundamentally that profiled abrasive brushing tools can be used to improve the quality of individual tooth flank surfaces. Due to the integration into the grinding machine, it represents a promising alternative to common finishing applications. Before the process can be used in an industrial environment, process reliability and tool life must be examined. For this purpose, complete reference gearwheels (39 × 10) were finished with the brushing tools. It could be shown that the surface roughness can be reliably reduced by ΔRa ≈ 0.2 µm by using a single brush for an entire gearwheel without changing the gear geometry. In addition to the influence of the tool specifications on the work result, the influence of the initial roughness after grinding was considered in particular. It was found that the achievable surface roughness depends significantly on the depth of the grinding grooves, as these are retained as desired, while the roughness peaks are fully smoothed. Furthermore, a device for the machine-integrated profiling and dressing of brushing tools was successfully designed, implemented, and tested.
  • Publication
    Application of Uncertainty-Aware Sensor Fusion in Physical Sensor Networks
    (IEEE, 2022)
    Gruber, Maximilian
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    Pilar von Pilchau, Wenzel
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    Gowtham, Varun
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    Koutrakis, Nikolaos-Stefanos
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    Schönborn, Nicolas
    ;
    Eichstädt, Sascha
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    Hähner, Jörg
    ;
    Corici, Marius-Iulian
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    Magedanz, Thomas
    ;
    Polte, Julian
    ;
    Uhlmann, Eckart
    Modern industrial processes often collect redundant information from multiple sensors. It is of interest to leverage this information to form a more accurate or robust estimate of an observed quantity utilizing a sensor fusion operation. To be able to comply with quality requirements on the fused value, preservation of traceability is required. Moreover, the sensor fusion needs to be implemented within suitable digital architectures for Industrial Internet of Things (IIoT) environments. In a continuation of previous work, this is achieved by the usage of digital twins that represent the entities of two IIoT testbeds and the adoption of a method for uncertainty-aware homogeneous sensor fusion, which is presented in full detail. Metrological traceability of the fused value is established by propagating the measurement uncertainty of the input sensor according to metrological standards. The method is implemented as a modular service connected to an existing IIoT architecture. The flexibility of the method is shown by application to two different scenarios with only minimal adaption efforts. The fused sensor values are (as indicated by earlier work) robust to outliers and perform well in practical scenarios within the chosen IIoT architecture.
  • Publication
    Revealing dynamic processes in laser powder bed fusion with in situ X-ray diffraction at PETRA III
    ( 2022)
    Krohmer, E.
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    Schmeiser, F.
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    Wahlmann, B.
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    Rosigkeit, J.
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    Graf, G.
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    Spoerk-Erdely, P.
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    Clemens, H.
    ;
    Staron, P.
    ;
    Körner, C.
    ;
    Reimers, W.
    ;
    Uhlmann, Eckart
    The high flux combined with the high energy of the monochromatic synchrotron radiation available at modern synchrotron facilities offers vast possibilities for fundamental research on metal processing technologies. Especially in the case of laser powder bed fusion (LPBF), an additive manufacturing technology for the manufacturing of complex-shaped metallic parts, in situ methods are necessary to understand the highly dynamic thermal, mechanical, and metallurgical processes involved in the creation of the parts. At PETRA III, Deutsches Elektronen-Synchrotron, a customized LPBF system featuring all essential functions of an industrial LPBF system, is used for in situ X-ray diffraction research. Three use cases with different experimental setups and research questions are presented to demonstrate research opportunities. First, the influence of substrate pre-heating and a complex scan pattern on the strain and internal stress progression during the manufacturing of Inconel 625 parts is investigated. Second, a study on the nickel-base superalloy CMSX-4 reveals the formation and dissolution of γ′ precipitates depending on the scan pattern in different part locations. Third, phase transitions during melting and solidification of an intermetallic γ-TiAl based alloy are examined, and the advantages of using thin platelet-shaped specimens to resolve the phase components are discussed. The presented cases give an overview of in situ X-ray diffraction experiments at PETRA III for research on the LPBF technology and provide information on specific experimental procedures.
  • Publication
    Performance analysis of an adaptive cooling system with primary and secondary heat paths for linear direct drives in machine tools
    ( 2022)
    Uhlmann, Eckart
    ;
    Salein, S.
    Machine tools subjected to high demands regarding productivity and accuracy are faced with the challenge that thermal losses influencing the accuracy negatively. Due to high requirements regarding thermal stability of precision related machine tool components, the focused linear direct drives (LDD) must be tempered by active cooling systems. In machine tools, a sufficient cooling capacity is available, but the cooling is insufficiently adjusted to the process and the individual demand of the heat-inducing as well as precision related components. With the intention to achieve a demand-oriented cooling, the use of thermoelectricity in machine tools is one research objective at the Institute for Machine Tools and Factory Management (IWF). Inspired by the concept of thermoelectric self-cooling (TSC)-systems for electronic devices, an Adaptive Cooling (AC)-system with thermoelectric generators (TEG) for LDD in machine tools is developed and experimentally investigated. In order to enhance the performance of AC-systems, in this research a reduction of the global thermal resistance is focused. A promising approach to achieve this goal is the division of the induced heat flow into a primary and a secondary heat path. For a model-based performance analysis of this approach, a system simulation is presented. To acquire experimental data for model validation, a test bench of the AC-system with primary as well as primary and secondary heat path is put into operation. The comparison of simulative and experimental determined data indicates a predominantly high model prediction accuracy. As a result, the implementation of a secondary heat path enables a reduction of the temperature on the upper surface of the heat source by 24.6% and thus a decrease of the global thermal resistance by 38.1%. Compared to the initial state of the AC-system only with primary heat path, the achieved thermal stability in the precision related machine tool component as well as the self-starting capability is improved.