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In subtractive manufacturing processes, swarf, burrs or other residues are produced, which can impair the function of a tribological system (e.g., journal bearings). To prevent premature engine damage, cleanliness requirements are defined for production processes. Damaging particle tests are an experimental approach for validating these defined cleanliness requirements. This methodical approach is not yet widely used. For one, the test setup must be developed and proven for the respective application. For another, in order to carry out the tests in a systematic manner, defined test particles with properties similar to those of the contaminants encountered in reality are required. In the second part of the paper, the process chain for manufacturing artificial test swarf by micro powder injection molding (MicroPIM) is described. The size and shape of the swarf were derived from real swarf via several abstraction processes. Although certain design guidelines for MicroPIM parts could not be taken into account, the targeted manufacturing tolerances were achieved in most cases. During demolding, it became apparent that the higher ejection forces of the free-formed geometries must be taken more into account in the design of the mold. The experiments on the test setup also revealed that the artificial test swarf was unexpectedly brittle and was therefore ground up in the bearing gap without causing any substantial damage to the bearing. Thus, the artificial test swarf in its current sintered state is not a suitable substitute for micromilled swarf. However, MicroPIM could still be used to manufacture test particles in applications involving lower mechanical forces. [ABSTRACT FROM AUTHOR]

In this fundamental work, a series of experiments were performed to define the optimal amount of dispersant and solid content for feedstock with and without ceramic fibers (Nextel 610). Based on these fixed conditions, investigations were carried out to discover the effects of binder system, fiber sizing, and increasing fiber content on mixing and viscosity. In addition, the effects of kneading temperature and time, fiber sizing, and different binder systems on fiber length were investigated using a measuring mixer, high-pressure capillary rheometer, and microscopy. Stearic acid, as a dispersant, modified the particle surface and improved the rheological properties. Moreover, increasing the solid content in the feedstocks led to an exponential growth of final torque and relative viscosity, because of the increasing friction between particles. Paraffin wax (PW)- and polyethylene glycol (PEG)-based feedstocks showed different mixing behaviors and rheological results with increasing fiber, whereas PEG-based feedstocks had higher final torques and kneading energies without fibers, whilst PEG feedstocks displayed lower viscosities. Consequently, during kneading, the amount of fiber has been predominating over fiber length, and the effect of the binder, the kneading temperature, and time did not cause significant changes. [ABSTRACT FROM AUTHOR]

Probably the most decisive benefit of Powder Injection Molding (PIM) is the wide range of materials. As a logical consequence current R+D activities target on the adaptation of new metal and ceramic materials. Modern high-performance materials like e.g. Ni-based super alloys are widely applied. For further progress development of so-called High-Entropy-Alloys (HEA) characterized by a minimum of five elements with all of nearly the same content, i.e. an equiatomar composition, started. These alloys represent a quite new field in metallurgy expected to offer attractive properties like high thermal strength and/or increased ductility. For initial trials a Co20Cr20Fe20Mn20Ni20 alloy was used. Injection and sintering procedures were developed and the resulting densities were examined. Processing of Ceramic Matrix Composites by PIM represents a considerable challenge. Development of a process chain for the ceramic injection molding of Al2O3 short fiber CMC has been performed. Fiber content varied between 10 to 50 vol.% whereas for binder a well-examined system from KIT was chosen. As expected the fiber content showed a major effect on the rheological properties and fiber orientation depended strongly on the apparent shear profile. Both parameters affected the sintering behavior as well. [ABSTRACT FROM AUTHOR]

Serial crystallography experiments at X-ray free-electron lasers can utilize specially designed ceramic nozzles to generate a strongly focused liquid jet of sample. Several nozzle design options have been evaluated and a concept using a sharpened glass capillary mounted in a self-centering ceramic nozzles is detailed. Filling simulations and tool construction are given for micro ceramic injection molding manufacture of the nozzles. Produced parts are found to meet the specifications for nozzle dimensions and bearing features. Functionality tests show superior performance with respect to liquid jet straightness and reproducibility compared to flame polished glass nozzles. [ABSTRACT FROM AUTHOR]

Material and process technology: To develop and use high-resilience ceramic and metal microcomponents, the entire process chain from prototype to volume production needs to be optimised. To achieve this, researchers are using microforming processes - and the results mean benefits for vehicles, medical devices and more. [ABSTRACT FROM AUTHOR]

The increasing importance of two-component microinjection molding is due to the potential to integrate different functionalities in one assembly without applying additional procedures. Furthermore, it enables a mass production technique of assemblies made up of two or more components. For mechanical advantages like toughness, hardness, or sufficient tribological behavior, metal or ceramic materials have to be used; the resulting process type is known as two-component micropowder injection molding (2C-MicroPIM). As this technology permits, in principle, the realization of fixed as well as movable junctions, a variety of new applications will be available. However, the two crucial aspects of 2C-MicroPIM research are the selection of adequate materials and an optimized process development. This article describes the challenges and approaches of the process development. The feasibility of ceramic 2C-MicroPIM assemblies has been demonstrated by a shaft-to-collar connection, which is composed by a zirconia gear wheel and a shaft made of alumina. [ABSTRACT FROM AUTHOR]

The progress in microinjection molding has paved the way for the fabrication of complex components. Particularly, the integration of different functionalities made possible by two-component injection molding is a challenging facet of this technology. For the production of robust microdevices consisting of two different metals or ceramics a special variant of this technology has to be implemented: two-component micropowder injection molding (2C MicroPIM). The study presents the materials and powder combinations suitable for 2C MicroPIM. The investigations included considerations on materials behavior during feedstock compounding, injection molding, debinding, and sintering of the assemblies. As a result of dilatometric measurements and on the basis of theoretical considerations and characterization of a 2C MicroPIM part at the phase boundary the requirements beneficial for either a fixed or a movable junction were defined. A shaft-to-collar connection was used to demonstrate the applicability of the selected materials. The investigated ceramic powders and the organic components for the feedstock development for the realization of a shaft-to-collar connection with 2C MicroPIM are clearly applicable when a dispersant like stearic acid is added. [ABSTRACT FROM AUTHOR]

Microminiature powder injection molding (μPIM) is a premising variant of powder injection molding (PIM) with development profiting by the demand for highly resistive micro products made of metal or ceramic materials, μPIM involves low-pressure or high-pressure injection molding; the former is commonly used for prototypes and small runs while the latter reflects medium and large-scale production. In relation to feedstock improvement, current research focuses on the exploitation of additives and the application of ultrafine powders. In terms of the μPIM shaping process, primary challenges are further miniaturization and the production of micro components with increased complexity. Presently, variants of multi-component μPIM are under development and the process parameters have to be adjusted for metals and ceramics to address issues of disconnection in micro areas. Examples are shaft-wheel combinations consisting of different couples of ceramics or metals. Depending on the powders and process parameters, mobile or immobile joints can be fabricated. [ABSTRACT FROM AUTHOR]

The success of labs- and organs-on-chips as transformative technologies in the biomedical arena relies on our capacity of solving some current challenges related to their design, modeling, manufacturability, and usability. Among present needs for the industrial scalability and impact promotion of these bio-devices, their sustainable mass production constitutes a breakthrough for reaching the desired level of repeatability in systematic testing procedures based on labs- and organs-on-chips. The use of adequate biomaterials for cell-culture processes and the achievement of the multi-scale features required, for in vitro modeling the physiological interactions among cells, tissues, and organoids, which prove to be demanding requirements in terms of production. This study presents an innovative synergistic combination of technologies, including: laser stereolithography, laser material processing on micro-scale, electroforming, and micro-injection molding, which enables the rapid creation of multi-scale mold cavities for the industrial production of labs- and organs-on-chips using thermoplastics apt for in vitro testing. The procedure is validated by the design, rapid prototyping, mass production, and preliminary testing with human mesenchymal stem cells of a conceptual multi-organ-on-chip platform, which is conceived for future studies linked to modeling cell-to-cell communication, understanding cell-material interactions, and studying metastatic processes. [ABSTRACT FROM AUTHOR]

Highlights: [•] Development of a fully automatic 2C-PIM tool. [•] Replicate fusion relevant components in one step without additional brazing. [•] No cracks or gaps in the seam of the joining zone visible. [•] For both material combinations a solid bond of the material interface was achieved. [•] PIM is a powerful process for mass production as well as for joining even complex shaped parts. [Copyright &y& Elsevier]