Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Application of laser surface nanotexturing for the reduction of peri-implantitis on biomedical grade 5 Ti-6Al-4V dental abutments
    ( 2019)
    Uhlmann, E.
    ;
    Schweitzer, L.
    ;
    Cunha, A.
    ;
    Polte, J.
    ;
    Huth-Herms, K.
    ;
    Kieburg, H.
    ;
    Hesse, B.
    The annual revenue of dental implants is estimated on 33 billion USD in 2019 and the efforts to keep the teeth functionality and aesthetics is continuously growing over the years. However, loosening of dental implants induced by infection is still a critical and common problem worldwide. In this scenario, the development of new implant manufacturing strategies is of utmost importance. Every surface exposed in the oral cavity, both the tooth and the implant surface, are covered by a layer of salivary proteins, the so-called pellicle. The initial formation of a pellicle is followed by the attachment of bacterial cells onto it. Well-developed biofilms on dental implant surfaces become the main source of pathogenic microbes causing Peri-Implantitis, which is one of the main causes of dental implant failure. The surface topography and chemical composition of an implant are key factors in controlling surface wettability, which directly affects the formation of the biological films. In this sense, ultrafast laser surface nanotexturing rises as a promising advanced technology for controlling implant surface biological properties. Laser-processing parameters such as laser wavelength l, fluence F and number of pulses N are essential for surface texturing. Thus, this paper presents promising results on the influence of different laser induced periodic surface structures (LIPSS) on the composition of the pellicle and the biofilm formation on biomedical grade 5 Ti-6Al-4V dental abutments. Moreover, a biofilm reactor was built and adapted to assess the effect of the LIPSS on the biofilm formation.
  • Publication
    Dry-EDM milling of micro-scale features with high speed rotating tungsten tube electrodes
    ( 2017)
    Uhlmann, E.
    ;
    Perfilov, I.
    ;
    Schimmelpfennig, T.-M.
    ;
    Schweitzer, L.
    ;
    Yabroudi, S.
    Micro electrical discharge milling is an alternative to die-sinking EDM for the machining of three-dimensional micro-structures or cavities with free-form surfaces. An important advantage provided by micro-EDM milling for this purpose is the possibility to use simple pin or tube electrodes with diameters de ⤠500 µm. This reduces the manufacturing costs of the workpiece and decreases the setup time for positioning electrodes. The high density of conventional dielectric fluids and the resulting small working gap cause a severe contamination of the working gap with particles and as a consequence short-circuits and process instability. The use of gaseous dielectrics, like compressed air, leads to enhancements in the flushing conditions and the cooling of the tool and workpiece electrodes. The gas is injected through the tube electrode under high pressure, resulting in high flow velocities and a removal of melted material from the working gap. A new spindle with a maximum rotation speed of n ⤠400,000 rpm was developed by the Institute for Machine Tools and Factory Management IWF of the Technische Universität Berlin for the realization of micro dry-EDM milling with tube electrodes. The high speed rotation of the tool electrode stabilizes the process and increases the material removal rate due to better flushing conditions. This paper presents the equipment and machining results of dry-EDM milling of simple micro-scale features.
  • Publication
    NC-form grinding of carbon fibre reinforced silicon carbide composite
    ( 2013)
    Uhlmann, E.
    ;
    Borsoi Klein, T.
    ;
    Schweitzer, L.
    ;
    Neubrand, A.
    This paper presents an approach for the development and optimization of the NC-form grinding technology for an efficient machining of carbon fibre reinforced silicon carbide composite (C/SiC). The C/SiC properties, the importance and the necessity of the application of a high performance grinding process for the machining of this innovative composite material are introduced first. Then, the methodologies and the experimental investigations of NC-form grinding with the application of several machining parameters and three distinct bond types (vitrified, metal and synthetic resin) of diamond mounted points for the abrasive machining of C/SiC are presented. In order to monitor and analyze the process, grinding forces, surface integrity of ground workpieces and grinding wheel wear are investigated. The results of this paper provide new information regarding the wear behavior of grinding tools and the optimized conditions for grinding of C/SiC.