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Im Rahmen dieses Beitrags wird das Schmelzeemulgieren als Verfahren zur Herstel-lung von Polymermikropartikeln vorgestellt. In diesem Prozess wird zunächst ein Polymergranulat in einer kontinuierlichen Phase in Gegenwart geeigneter Additive in einem Rührbehälter aufgeschmolzen, die Rohemulsion in einer Rotor-Stator-Einheit feinemulgiert und anschließend zu einer Suspension abgekühlt. Der Einfluss von Prozessparametern und Systemzusam-mensetzung auf das Emulgierergebnis wird diskutiert und die Anwendbarkeit des Verfahrens für polymere Mikropartikeln anhand von Polypropylen (PP) und Polyethylen (PE-HD) dargestellt. Die erhaltenen Suspensionen werden zur Überführung in Pulverform sprühgetrocknet und die Fließeigenschaften des Pulvers analysiert. Durch trockenes Beschichten mit pyrogener Kieselsäure kann die Fließfähigkeit der erhaltenen Partikeln weiter verbessert werden. Das Verfahren bietet somit einen neuen Zugang zur Herstellung neuer Ausgangsmaterialien für die Additive Fertigung.
In former works, the optical material properties of different polymer powders used for Laser Beam Melting (LBM) at room temperature have been analyzed. With a measurement setup using two integration spheres, it was shown that the optical material properties of polymer powders differ significantly due to multiple reflections within the powder compared to solid bodies of the same material. Additionally, the absorption behavior of the single particles shows an important influence on the overall optical material properties, especially the reflectance of the powder bed. Now the setup is modified to allow measurements at higher temperatures. Because crystalline areas of semi-crystalline thermoplastics are mainly responsible for the absorption of the laser radiation, the influence of the temperature increase on the overall optical material properties is analyzed. As material, conventional polyamide 12 and polypropylene as new polymer powder material, is used. By comparing results at room temperature and at higher temperatures towards the melting point, the temperature-dependent optical material properties and their influence on the beam-matter interaction during the process are discussed. It is shown that the phase transition during melting leads to significant changes of the optical material properties of the analyzed powders.
Heat staking is a joining technology by which thermoplastic pins are formed by force and temperature to create a form- and force-fitting connection between components. This paper examines the characteristics of 3D printed pins in comparison to conventionally turned pins for heat staking applications. The 3D printed pins are created using fused layer modeling, with variations in horizontal and vertical building directions, as well as different layer thicknesses. The study investigates the impact of significant factors on the heat staking process, including the forming force and temperature. Tensile tests, micrographs, and micro-CT measurements were conducted to determine the properties of the heat-staked joints. Additionally, a stage plan was developed to enhance the understanding of the forming process of both printed and conventionally turned materials. The findings suggest that, under specific process parameters, 3D printed pins exhibit comparable strength to conventionally manufactured pins. The research also demonstrates that the anisotropy resulting from the layer-by-layer construction of the pins significantly influences the strength of the connection. Furthermore, the study reveals that 3D printed pins exhibit good forming accuracy during the heat staking process, and the cavities formed during printing can be substantially reduced.