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Author: search.filters.author.Gundelsweiler, BerndSubject: search.filters.subject.620

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    Adhesion-induced demolding forces of hard coated microstructures measured with a novel injection molding tool
    (2023) Schoenherr, Maximilian; Ruehl, Holger; Guenther, Thomas; Zimmermann, André; Gundelsweiler, Bernd
    The demolding of plastic parts remains a challenging aspect of injection molding. Despite various experimental studies and known solutions to reduce demolding forces, there is still not a complete understanding of the effects that occur. For this reason, laboratory devices and in-process measurement injection molding tools have been developed to measure demolding forces. However, these tools are mostly used to measure either frictional forces or demolding forces for a specific part geometry. Tools that can be used to measure the adhesion components are still the exception. In this study, a novel injection molding tool based on the principle of measuring adhesion-induced tensile forces is presented. With this tool, the measurement of the demolding force is separated from the actual ejection step of the molded part. The functionality of the tool was verified by molding PET specimens at different mold temperatures, mold insert conditions and geometries. It was demonstrated that once a stable thermal state of the molding tool was achieved, the demolding force could be accurately measured with a comparatively low force variance. A built-in camera was found to be an efficient tool for monitoring the contact surface between the specimen and the mold insert. By comparing the adhesion forces of PET molded on polished uncoated, diamond-like carbon and chromium nitride (CrN) coated mold inserts, it was found that a CrN coating reduced the demolding force by 98.5% and could therefore be an efficient solution to significantly improve demolding by reducing adhesive bond strength under tensile loading.
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    Hybrid solenoids based on magnetic shape memory alloys
    (2023) Mauch, Manuel; Hutter, Marco; Gundelsweiler, Bernd
    The mobility of today and tomorrow is characterized by technological change and new challenges in drive concepts such as electric or hydrogen vehicles. Abolishing conventional combustion engines creates even more need for switching or valve technology in mobility systems. For switching and controlling purposes, solenoids are used in large numbers and in a wide variety of applications, thus making a significant contribution to the overall success of the energy transition, and not only in the automotive sector. Despite their long existence, continued research is being carried out on solenoids involving new materials and actuator concepts. Great interest is focused on providing an adjustable force-displacement characteristic while simultaneously reducing the noise during switching. At IKFF, research is being conducted on hybrid electromagnets in the border area of switching and holding solenoids. This paper aims to present the major advantages of this hybrid drive concept based on an electromagnetic FEA simulation study of two drive concepts and specially developed and characterized prototypes with magnetic shape memory (MSM) alloys. The concepts differ in the spatial orientation of the MSM sticks to generate an active stroke of the plunger, which contributes to a beneficial force-displacement characteristic and lower power consumption while minimizing switching noise.