Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Measurement of in-mould shear rates by x-ray particle image velocimetry
    ( 2017)
    Uhlmann, E.
    ;
    Hein, C.
    ;
    Oberschmidt, D.
    The manufacturing of large quantities of polymeric optical and micro-optical components becomes more and more important regarding industrial applications as MEMS devices, customer electronics or micro imaging systems. The relevant parameters for the qualification of polymeric micro optics as surface roughness, shape and positional tolerances, refractive index, molecular orientation, injection moulding process induced deviations and their connection to injection moulding parameters are largely known. The manufacturing of micro optics by micro injection moulding and associated with that, micro injection moulding machine tools with highly complex plastification and injection systems is far less understood. In particular, the influence of shear loads and temperature deviation on replication quality has not been fully investigated. The occurring shear rates during injection moulding lead to mechanical damage of the polymer on a molecular level and reduced optical functionality. This work presents an approach for in mould shear rate measurement by the use of a metrological computed tomography system. Using metal powder with a particle size 3 mm < dp < 5 mm as tracer particles, Polyetheretherketon (PEEK) as mould material, a Zeiss Metrotom 800 computer tomography system and a Babyplast injection unit, streamlines of polymer flow could be visualized. In accordance to optical particle image velocimetry (PIV), for each frame a matrix including particle position was calculated. The temporal shift of these positions lead to velocity gradients that allow the calculation of shear-rates . By reproducing relevant elements of injection units and mould structures, this works enables the profound investigation of fluid dynamics regarding micro injection moulding and the correlation between shear loads and polymer characteristics.
  • Publication
    Generative tool manufacturing for the replication of micro-optical components
    ( 2014)
    Uhlmann, E.
    ;
    Hein, C.
    ;
    Bergmann, A.
    ;
    Oberschmidt, D.
  • Publication
    Machining of microfluidic structures for biotechnological components
    ( 2013)
    Uhlmann, E.
    ;
    Oberschmidt, D.
    ;
    Hein, C.
    ;
    Mahr, F.
  • Publication
    General detection of microbial contamination in technical fluids
    ( 2012)
    Langbein, J.E.
    ;
    Hein, C.
    ;
    Spielvogel, A.
    ;
    Lorenz, D.
    ;
    Stahl, U.
    ;
    Oberschmidt, D.
    ;
    Uhlmann, E.
    This work presents first results of a new approach for the detection of biological contamination using the Surface Plasmon Resonance (SPR) spectroscopy. SPR sensors have been commonly employed for the detection of proteins, bacteria and chemical substances. However, only specific interactions can be detected so far that rely on specific and sensor immobilized receptor molecules. It is of importance to overcome this limitation as technical fluids like cooling lubricants, paints and varnishes often show contaminations with different strains of microorganisms. The here presented general approach will focus on a distinguished mode of action. The aim is an unspecific adsorption of bacteria and other microorganisms to differently processed metal surfaces. The processed sensor surface is characterized by means of contact angle measurements, scanning electron microscopy, and bacterial and fungal binding studies. Besides, one of the main advantages of the sensor is the usability in a multitude of liquids such as deeply contaminated emulsions and other technical fluids, providing a broad applicability of the sensor system.