Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Development of a mechanical, biocide-free method of disinfection for cathodic dip coating processes
    ( 2021)
    Uhlmann, Eckart
    ;
    Hilt, Michael
    ;
    Hein, Christoph
    ;
    Cudazzo, Markus
    ;
    Huth-Herms, Katrin
    ;
    Jahnke, Christian
    ;
    Quast, Melanie
    Technical fluids are often contaminated by bacteria as Burkholderia cepacia (B. cepacia), which is found in different industrial issues and affects manufacturing process chains by the formation of planktonic cell-aggregates and biofilms within the working fluids. B. cepacia is one of nine species of the Burkholderia cepacia complex (Bcc), a group of gram-negative, motile, non-spore-forming, and rod-shaped bacteria. Because of the opportunistic pathogenicity to plants, animals, humans, and the multi-drug and biocide resistance, B. cepacia is difficult to treat. This study aims to provide an application to reduce the germ numbers ng in an eco-friendly and continuous process without the use of biocides. The approach to disinfect technical fluids is to apply high shear forces in a rotor-stator assembly to the fluid. A prototype of the rotor-stator assembly with a variably adjustable shear gap gs and rotor speed srot was constructed. First experiments with a frequency frot 1 0 Hz ⤠frot ⤠40 Hz a shear gap gs = 83 µm and gs = 166 µm showed a reduction of germ number ngr = 99.6 %. It concluded that the disinfection of technical fluids by a rotor-stator assembly is a biocide-free alternative. In addition to defined process parameters such as shear gap gS, temperature Ï, frequency frot and time of machining process tmp, also the peripheral speed vp, rotational speed vrot, flow rate fr and shear stresses Ï were used to assess the machining result and to develop an overall concept for disinfection of technical fluids.
  • Publication
    Micro-milling of a sprue structure in tungsten carbide-based metal matrix composite
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Polte, Mitchel
    ;
    Hein, Christoph
    ;
    Hocke, Toni
    ;
    Jahnke, Christian
    Many industries rely on plastic components manufactured by micro-injection moulding. There is a high potential to further increase the cost-effectiveness by machining the moulds needed for this process from non-ferrous metals and reinforcing the parts of the mould, which experience high loads during the micro-injection moulding. Inserting tungsten carbide particles locally into the surface of these non-ferrous metals is one possibility of reinforcement. The resulting metal-matrix-composites (MMC) exhibit the needed wear resistance, while the ground material can be machined very effectively through micro-milling. In contrast, the Micro-milling of these MMC-materials is challenging and so far not state of the art. Thus, this investigation is concerned with the development and qualification of micro-milling parameters for tungsten carbide-based MMC-materials. Binderless polycrystalline diamond as innovative cutting material was applied for this purpose. The goal of the mil ling parameter development was to optimize the surface roughness and the form accuracy for machining an aluminium bronze workpiece reinforced with tungsten carbide particles through laser injection. Based on an analysis of a wide range of process parameters, an optimised milling strategy was applied to machine a sprue structure from the described MMC-material. Different parameter sets are evaluated by analysing the form accuracy and measuring the surface roughness of machined structures. A surface roughness of Ra = 80 nm and form accuracy of a = 3 µm could be achieved with optimized micro-milling parameters and qualified the developed parameters for industrial applications.
  • Publication
    Tool wear prevention in ultra-precision polymer machining
    ( 2020)
    Uhlmann, Eckart
    ;
    Fang, F.
    ;
    Polte, Julian
    ;
    Hein, Christoph
    ;
    Lai, M.
    ;
    Dörr, Martin
    ;
    Jahnke, Christian
    Polymers become more relevant in the field of optical components as their optical properties, like refractive index n and wavelength dependent dispersion n = f(λ), can be adjusted easily by additives. Due to their low density Ï polymeric optics are lightweight compared to glasses. The demand for ultra-precision machined polymer lenses is increasing. Small series and individualised components can only be produced economically by using ultra-precision machining. Within theses studies the influence of different measures to reduce diamond tool wear occurring during ultra-precision diamond face turning of polycarbonate (PC) and polysulfone (PSU) will be investigated. Continuous and interrupted face turning experiments are conducted to analyse the effects from separation of the diamond tool and workpiece. Results show increasing tool wear in interrupted cutting. Changes of the environmental conditions in the cutting process show an influence of increasing humidity H on diam ond tool wear. This contribution gives a qualitative and quantitative overview on the influencing factors on diamond tool wear in ultra-precision turning of polymers and gives an outlook on strategies to avoid its occurrence.