Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK
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PublicationDevelopment of a mechanical, biocide-free method of disinfection for cathodic dip coating processes( 2021)
;Uhlmann, E. ;Hilt, M. ;Hein, C. ;Cudazzo, M. ;Huth-Herms, K. ;Jahnke, C.Quast, M.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 â¤ frot â¤ 40 Hz a shear gap gs = 83 Âµm and gs = 166 Âµm 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.
PublicationApplication 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.
PublicationEffect of cooling lubricant on surface roughness for turning stainless steel with binderless-cBN( 2016)
;Uhlmann, E. ;Oberschmidt, D. ;Polte, J. ;Polte, M.Huth-Herms, K.Binderless-cubic Boron Nitride (cBN) from the company SUMITOMO CORPORATION, Itami, Japan, is one of the most promising cutting materials providing the opportunity for direct cutting of steel with ultra-precision (UP) quality without additional equipment or coating of the workpiece. This work presents the latest development in the field of precision machining of hardened stainless steel with binderless-cBN. In this paper the influence of the feed f and the cooling lubricant on the surface roughness is shown for turning the hardened stainless steel STAVAX ESR (H = 52 HRC) from the company BÖHLER-UDDEHOLM, Düsseldorf, Germany. A surface roughness Ra = 9 nm and Rz = 42 nm could be achieved using binderless-cBN and the cooling lubricant W200SL of the company OPORTET, Duisburg, Germany.