Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Simulativer Vergleich tubularer Peltierelemente
    ( 2022)
    Binninger, Roland
    ;
    Pernau, Hans-Fridtjof
    ;
    Schäfer-Welsen, Olaf
    ;
    Triebel, Florian
    ;
    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
    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
    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
    Wolframschmelzcarbidbasierte MMC-Schichten für den industriellen Einsatz im Formenbau
    ( 2022)
    Langebeck, Anika
    ;
    Jahnke, Christian
    ;
    Wünderlich, Tim
    ;
    Hein, Christoph
    ;
    Bohlen, Annika
    ;
    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.
    ;
    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
    Application of Uncertainty-Aware Sensor Fusion in Physical Sensor Networks
    (IEEE, 2022)
    Gruber, Maximilian
    ;
    Pilar von Pilchau, Wenzel
    ;
    Gowtham, Varun
    ;
    Koutrakis, Nikolaos-Stefanos
    ;
    Schönborn, Nicolas
    ;
    Eichstädt, Sascha
    ;
    Hähner, Jörg
    ;
    Corici, Marius-Iulian
    ;
    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
    High-Performance Electro-Discharge Drilling with a Novel Type of Oxidized Tool Electrode
    ( 2022)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Streckenbach, Jan
    ;
    Dinh, Ngoc Chuong
    ;
    Yabroudi, Sami
    ;
    Polte, Mitchel
    ;
    Börnstein, Julian
    Electro-discharge drilling is a key technology for manufacturing sophisticated nozzles in a broad range of automotive and aerospace applications. The formation of debris in the working gap leads to arcs and short circuits on the lateral surface when state-of-the-art tool electrodes are used. As a result, limited drilling depth, increased linear tool wear, and the conicity of boreholes are still challenges. In this work, a new approach for the passivation of the lateral surface of copper tool electrodes by oxidation is shown. The comparison with state-of-the-art tool electrodes showed a reduction in the erosion duration by 48% for machining hardened steel. Promising improvements could be achieved by the thermal oxidation of the tool electrodes with the aim of increasing the electrical resistivity of the lateral surface of the tool electrode. However, due to the loss of strength, the high oxide layer thickness, and the partial delamination of the oxide layer, further comprehensive investigations on the influence of the oxidation temperature need to be conducted. Future adjustments with lower oxidation temperatures will be carried out.
  • Publication
    Practical Approaches for Acoustic Emission Attenuation Modelling to Enable the Process Monitoring of CFRP Machining
    ( 2022)
    Uhlmann, Eckart
    ;
    Holznagel, Tobias
    ;
    Clemens, Robin
    Acoustic emission-based monitoring of the milling process holds the potential to detect undesired damages of fibre-reinforced plastic workpieces, such as delamination or matrix cracking. In addition, abrasive tool wear, tool breakage, or coating failures can be detected. As measurements of the acoustic emission are impacted by attenuation, dispersion, and reflection as it propagates from source to sensor, the waveforms, amplitudes, and frequency content of a wave packet differ depending on the propagation length in the workpiece. Since the distance between acoustic emission sources and a stationary sensor attached to the workpiece changes continually in circumferential milling, the extraction of meaningful information from the raw measurement data is challenging and requires appropriate signal processing and frequency-dependent amplification. In this paper, practical and robust approaches, namely experimentally identified transfer functions and frequency gain parameter tables for attenuation modelling, which in reverse enable the reconstruction of frequency spectra emitted at the acoustic emission source, are presented and discussed. From the results, it is concluded that linear signal processing can largely compensate for the influence of attenuation, dispersion, and reflection on the frequency spectra and can therefore enable acoustic emission based process monitoring.
  • Publication
    Prediction of the Roughness Reduction in Centrifugal Disc Finishing of Additive Manufactured Parts Based on Discrete Element Method
    ( 2022)
    Kopp, Marco
    ;
    Uhlmann, Eckart
    One major drawback of additive manufacturing is the poor surface quality of parts, which negatively affects mechanical and tribological properties. Therefore, a surface finishing is necessary in most cases. Due to a high material removal rate, centrifugal disc finishing is a promising mass finishing operation for an effective surface finishing of additive manufactured parts. However, due to machining the workpieces in a freely movable manner, the process is hardly controllable, and the process design is often based on time-consuming and cost-intensive trial-and-error approaches. Especially when it comes to the machining of complex-shaped workpieces, finishing results are barely predictable. Therefore, the aim of this study is to set up a numerical simulation of the centrifugal disc finishing based on the Discrete Element Method (DEM) to predict finishing results. A procedure to determine the required DEM input parameters is presented and the simulation was validated using a freely movable force sensor. The results of the finishing experiments with additive manufactured workpieces made of Ti-6Al-4V were correlated with the simulated results. The derived correlation was used to predict local differences in the roughness reduction, which occurred when finishing workpieces with a limited accessibility to the surface. As a result, it is concluded that the complex relationship between the type of media, the accessibility to the surface, and the achievable finishing results can be modeled using the DEM.