Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • 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
    Heat treatment of SLM-LMD hybrid components
    ( 2019)
    Uhlmann, Eckart
    ;
    Düchting, Jan
    ;
    Petrat, Torsten
    ;
    Graf, Benjamin
    ;
    Rethmeier, Michael
    Additive manufacturing is no longer just used for the production of prototypes but already found its way into the industrial production. However, the fabrication of massive metallic parts with high geometrical complexity is still too time-consuming to be economically viable. The combination of the powder bed-based selective laser melting process (SLM), 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 process duration. For the industrial application of the SLM-LMD hybrid process chain it is necessary to investigate the interaction of the processes and its effect on the material properties to guarantee part quality and prevent component failure. Therefore, hybrid components are manufactured and examined before and after the heat treatment regarding the microstructure and the hardness in the SLM-LMD transition zone. The experiments are conducted using the nickel-based alloy Inconel 718.
  • Publication
    In-Situ-Kraftmessung bei variablen Werkzeugwinkeln
    ( 2019)
    Uhlmann, Eckart
    ;
    Uhlemann, Sebastian
    ;
    Kochan, Jaroslaw
    Werkzeugentwicklungen sind von iterativen Anpassungen und aufwendigen Versuchsreihen mit einer Vielzahl von Prototypen geprägt. In einem Forschungsprojekt wurde ein sensorisch instrumentiertes Fräswerkzeug mit verstellbaren Schneiden entwickelt und mittels SLM (Selective Laser Melting) aufgebaut. Mit dieser Entwicklung liegt ein Instrument vor, das im Fräsprozess unmittelbar an den Schneiden Belastungen erfassen kann und durch nachgestellte FEM (Finite Elemente Methode)-Analysen und Optimierungsroutinen ein enormes Potenzial für die Auslegung optimierter Werkzeuggeometrien bietet.
  • Publication
    Manufacturing and replication of sub-10 mm micro-bowls for biomedical sensor systems
    ( 2018)
    Uhlmann, Eckart
    ;
    Hein, Christoph
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Dähne, L.
    The technical implementation of a novel biosensor for the highly parallelized screening of biochemical binding reactions depends on the manufacturing of an array of micro-bowls with a diameter dB 10 µm with an aspect ratio ar 1. Since the operating principle of the biosensor is based on the stimulation of stationary optical waves in micro-spheres, micro-bowls for the immobilisation of these spheres in a microfluidic environment are necessary. Due to this operating principle, the micro-bowls need to separate the spheres from the fluid flow and ensure the careful adherence of single spheres, coincidently. Moreover, the pathway for the optical accessibility of the micro spheres should be unrestricted. This work presents a process chain for the manufacturing of microfluidic chips with an array of n 1,000 micro-spheres by ultra-precision milling of mold inserts, the replication by precision injection molding as well as experimental trial results. With regard to manufacturing of the mold inserts, the uniform and burr free ultraprecision milling of large aspect ratio micro posts was investigated within a parametric study. Furthermore, the replication of the micro-bowls was examined by taking the consistent replication of the entire bowl array, the adverse formation of fillets, and the replication of surfaces with optical functions into special account. By the analysis of the microfluidic and optical properties of the replicated structures, the correlation between mold manufacturing, replication, and operating conditions can be performed.
  • Publication
    The Effects of Laser Microtexturing of Biomedical Grade 5 Ti-6Al-4V Dental Implants (Abutment) on Biofilm Formation
    ( 2018)
    Uhlmann, Eckart
    ;
    Schweitzer, Luiz
    ;
    Kieburg, Heinz
    ;
    Spielvogel, Anja
    ;
    Huth-Herms, Katrin
    Every surface exposed in the oral cavity is covered by a layer of salivary proteins (pellicle). The initial formation of the pellicle, which is a cellular, proteinaceous film on the surface, is followed by the adsorption of bacterial cells. Well-developed biofilms on dental implant surfaces become the main source of pathogenic microbes causing Peri-Implantitis, a condition that has been described as one of the main causes of dental implant failure. The surface wettability affects the formation of pellicle and biofilms. This paper presents laser surface microtexturing as a surface treatment of Ti-6Al-4V against the settlement of the bacteria Streptococcus mutans.
  • Publication
    Potentials and limitations of simulation based artefact correction in computed tomography
    ( 2018)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Melnik, Steffen
    In computed Tomography common artefact correction methods generally address one type of artefacts, thus in praxis usually a combination of different methods is used. Without expert knowledge the user of 3D X-ray scanners is frequently over-challenged figuring out what kind of correction method should be used and when. Simulation based artefact correction in contrast is capable of dealing with multiple kinds of artefacts simultaneously. This includes e.g. beam hardening, partial volume artefacts, off-focal radiation and scatter. The simulation based approach uses prior knowledge about the specimen and the X-ray parameters for calculation of artificial projection images. While in medicine the structure of the specimen (patient) is generally unknown, in field of none destructive testing and quality assurance specimens often exists in form of design data. During simulation based artefact correction artificial images are calculated for every measured projection. Aim is the identification and correction of corrupted projection integrals. A common example is scatter correction, where scatter distribution is determined by Monte-Carlo simulation. For correction the scatter is subtracted from measured projection data, resulting in reduced inconsistencies and enhanced signal-to-noise ratio (SNR). Subsequently, the corrected image data is used for 3Dreconstruction. Although simulation based artefact correction is capable of enhancing 3D image quality, physically correct simulation of projection data can be challenging in terms of accuracy and runtime. Especially when the simulation includes a large variety of artefacts. The aim of this paper is to show the potentials and limitations of simulation based artefact correction algorithms and to discuss the need for full Monte-Carlo method. Furthermore, the requirements for optimal simulation results are determined.
  • Publication
    Wear behaviour of HIPIMS coated micro-milling tools with cutting edge preparation for machining steel moulds
    ( 2018)
    Uhlmann, Eckart
    ;
    Kuche, Yves
    ;
    Polte, Julian
    ;
    Polte, Mitchel
    Micro-milling is an appropriate process for the industrial production of precision parts in the mould and die industry. Decisive for a long tool life is the wear resistance, which can be improved by cutting edge preparation technologies and tool coatings. Especially the improvement of the coating technology with the high power impulse magnetron sputtering (HIPIMS) provides improved tool wear behaviour and longer path length lc. Further studies compare two different HIPIMS-coatings of micro-milling tools for machining the mould steel X13NiMnCuAl4-2-1-1. Furthermore, the tool wear could be reduced due to cutting edge preparation using immersed tumbling process. In consequence of the increased cutting edge radii rβ the measured active forces Fa increased slightly. Best results were achieved for micro-milling tools with cutting edge preparation and AlTiN coating.