TY - JOUR A1 - Stichel, Thomas A1 - Laumer, Tobias A1 - Linnenweber, Tim A1 - Amend, Philipp A1 - Roth, Stephan T1 - Mass Flow Characterization of Selective Deposition of Polymer Powders with Vibrating Nozzles for Laser Beam Melting of Multi-material Components JF - Physics Procedia N2 - The generation of multi-material components by laser beam melting (LBM) is a challenge which requires the invention of new coating devices for preparation of arbitrary powder patterns. One solution is the usage of vibration-controlled nozzles for selective deposition of polymer powders. Powder flow can be initiated by vibration enabling a start-stop function without using any mechanical shutter. In this report, the delivery of polymer powder by vibrating nozzles is investigated with respect to their application in LBM machines. Therefore, a steel nozzle attached to a piezo actor and a weighing cell is used in order to measure the stability and time-dependence of the powder mass flow upon vibration excitation with the usage of different kind of powder formulations. The results show that precompression of the powder inside the nozzle by vibration excitation is essential to realize a reliable start-stop function with reproducible discharge cyles and to prevent a initial flush of powder flow. Moreover, the use of different powder materials showed that mass flow is even possible with powders which are not optimized regarding flowability, but is readily enhanced with a factor of 2 to 3 by admixing Aerosil® fumed silica. KW - laser beam melting KW - multi-material deposition KW - polymer powder KW - vibration-controlled powder nozzle Y1 - 2016 U6 - https://doi.org/10.1016/j.phpro.2016.08.099 SN - 1875-3892 SN - 1875-3884 VL - 83 SP - 947 EP - 953 PB - Elsevier CY - Amsterdam [u.a.] ER - TY - CHAP A1 - Stichel, Thomas A1 - Amend, Philipp A1 - Laumer, Tobias A1 - Roth, Stephan T1 - Multi-material deposition of polymer powders with vibrating nozzles inside laser beam melting machines T2 - 6th International Conference on Additive Technologies - iCAT 2016 : proceedings : Nürnberg, Germany, 29.-30. November 2016 N2 - The generation of multi-material components using Laser beam melting (LBM) is a challenge which requires the invention of new coating devices for the preparation of arbitrary powder patterns. One solution is the usage of vibration-controlled nozzles for selective deposition of polymer powders. Powder flow can be initiated by vibration even when using powders with low flowability. In this report, the selective deposition of polymer powder by vibrating nozzles is investigated with respect to their application in LBM machines. Therefore, a steel nozzle attached to a piezo actor is applied, whereas the nozzle itself features internal channels which allow the precise control of the powder temperature using heat transfer oil. The setup is used to study the influence of temperature on the powder mass flow. The results show that, next to the vibration mode, the temperature strongly influences the powder mass flow which is done by affecting the moisture and thus the particle-particle adhesion forces. This shows that a precise control of the powder temperature inside the nozzle is required in order to achieve a constant mass flow and thus a successful application of vibrating nozzles inside LBM machines. KW - laser beam melting KW - multi-materialdeposition KW - PA12 KW - polyamide 12 KW - vibration-controlled powder nozzle Y1 - 2016 PB - Interesansa - zavod CY - Ljubljana ER - TY - CHAP A1 - Laumer, Tobias A1 - Roth, Stephan A1 - Stichel, Thomas A1 - Schmidt, Michael T1 - Strategien zur Erzeugung von dreidimensionalen Multi-Material-Bauteilen T2 - 4. Industriekolloquium des Sonderforschungsbereichs 814 - Additive Fertigung 814, 2015, Nürnberg Y1 - 2015 UR - https://www.researchgate.net/publication/295860904_Strategien_zur_Erzeugung_von_dreidimensionalen_Multi-Material-Bauteilen SN - 978-3931864651 SN - 3931864650 ER - TY - CHAP A1 - Stichel, Thomas A1 - Amend, Philipp A1 - Laumer, Tobias A1 - Roth, Stephan T1 - Electrostatic Multi-Material Powder Deposition for Simultaneous Laser Beam Melting T2 - International Conference on Information, Communication and Automation Technologies (ICAT), 2014, Wien N2 - In this paper, the use of electrostatic polymer powder transfer methods for the preparation of multi-material layers is discussed with respect to the application in Simultaneous Laser Beam Melting (SLBM). Therefore, the basic principles of the single process steps as well as the challenges in combination with SLBM are considered verifying the critical process steps. On that base, process concepts are developed which might enable the fabrication of high quality multi-material parts in the future. Moreover, since the polymer powders typically used with Laser Beam Melting differ strongly from common toners for e. g. electrophotographic printing, an experimental setup was built to study the powder transfer with an electrically chargeable transfer plate using polyamide 12 powder. The results of this study show that transfer of powders usable for Laser Beam Melting can be achieved, but depends on the electric field strength which is a function of the gap between transfer and substrate plate and the intermediate electric potential. Y1 - 2014 UR - https://www.researchgate.net/publication/280154608_Electrostatic_Multi-Material_Powder_Deposition_for_Simultaneous_Laser_Beam_Melting ER - TY - JOUR A1 - Stichel, Thomas A1 - Amend, Philipp A1 - Laumer, Tobias A1 - Roth, Stephan T1 - Polymer Powder Deposition using Vibrating Capillary Nozzles for Additive Manufacturing JF - Information, Communication and Automation Technologies (ICAT), 2014, Wien N2 - Abstract — In this report, the dry delivery of polyamide 12 (PA 12) powder for the preparation of powder layers in laser beam melting (LBM) is investigated. Therefore, an experimental setup was built which consists of a glass nozzle assembled on a piezo-electric actuator. By applying a sinusoidal voltage signal to the actuator, the nozzle is set into vibration mode which enhances the powder delivery through the nozzle. By using this effect, powder mass flow is controlled and a valve-like start and stop function is realized. In order to identify suitable process parameters, a broad range of vibration modes were investigated using two nozzles made from glass with different orifice diameters. Therefore, the vibration frequency and the voltage signal of the actuator were varied and the resulting mass flow was detected by a balance. It was found that both the frequency and the voltage signal affect the mass flow and its stability but with different impact. Moreover, powder lines were deposited with different velocities in order to characterize the setup regarding applicability for highly selective powder deposition for LBM. KW - multi-material deposition KW - additive manufacturing KW - vibrating nozzle KW - dry powder delivery KW - polyamide 12 Y1 - 2014 ER - TY - JOUR A1 - Stichel, Thomas A1 - Laumer, Tobias A1 - Baumüller, Tobias A1 - Amend, Philipp A1 - Roth, Stephan T1 - Powder Layer Preparation Using Vibration-controlled Capillary Steel Nozzles for Additive Manufacturing JF - Physics Procedia N2 - In this report, the dry delivery of polyamide 12 powders by vibrating capillary steel nozzles is investigated and discussed regarding its potential for powder layer preparation in Laser Beam Melting. Therefore, a setup including a steel nozzle assembled on a piezoelectric actuator is presented, which enables the precise control over very small powder quantities by vibration excitation. An analysis reveals that the mass flow through the nozzle can be adjusted by the vibration modes in a certain range depending on the nozzle's specifications, whereas the vibration modes themselves show a complicated behaviour. Using a positioning system in combination with the vibrating nozzle, single-layer patterns consisting of polyamide 12 are produced and characterized regarding surface homogeneity and selectivity using a laser stripe sensor. KW - additive manufacturing KW - dry powder delivery KW - multi-material deposition KW - polyamide 12 KW - vibrating nozzle Y1 - 2014 U6 - https://doi.org/10.1016/j.phpro.2014.08.158 SN - 1875-3892 SN - 1875-3884 VL - 56 SP - 157 EP - 166 PB - Elsevier ER - TY - JOUR A1 - Laumer, Tobias A1 - Wudy, Katrin A1 - Drexler, Maximilian A1 - Amend, Philipp A1 - Roth, Stephan A1 - Drummer, Dietmar A1 - Schmidt, Michael T1 - Fundamental investigation of laser beam melting of polymers for additive manufacture JF - Journal of Laser Applications N2 - By selective laser sintering (SLS), polymer powders are molten layer by layer to build conventional prototypes or parts in small series with geometrical freedom that cannot be achieved by other manufacturing technologies. The SLS process is mainly defined by the beam–matter interaction between powder material, laser radiation and different material characteristics by itself. However the determination of these different material characteristics is problematic because powder material imposes certain requirements that cannot sufficiently be provided by conventional measurement methods. Hence new fundamental investigation methods to determine the optical and thermal material characteristics like the thermal diffusivity, thermal conductivity, or the influence of different heating rates on the melting behavior are presented in this paper. The different analysis methods altogether improve the process of understanding to allow recommendations for the future process controlling. Y1 - 2014 U6 - https://doi.org/10.2351/1.4892848 SN - 1938-1387 SN - 1042-346X VL - 26 IS - 4 PB - AIP Publishing ER - TY - CHAP A1 - Laumer, Tobias A1 - Stichel, Thomas A1 - Amend, Philipp A1 - Roth, Stephan A1 - Schmidt, Michael T1 - Analysis of Temperature Gradients during Simultaneous Laser Beam Melting of Polymers T2 - Physics Procedia N2 - By simultaneous laser beam melting (SLBM), different polymer powders can be processed to multi-material parts, which offers the potential to enlarge the field of application for conventional LBM. In a SLBM process, a powder bed consisting of different polymers and therefore with different melting and crystallization temperatures is deposited. Besides the use of infrared emitters for preheating the lower melting polymer, a CO2 laser distributes the necessary preheating temperature of the higher melting polymer. In the last step, a thulium fibre laser distributes the energy necessary for melting the two preheated powders simultaneously. In order to analyze the temperature gradients of the process on the powder surface and in deeper layers, a high-resolution thermal imaging system and thermocouples are used. KW - Additive manufacturing KW - Multi-Material Parts KW - Process Qualification KW - Simultaneous Laser Beam Melting Y1 - 2014 U6 - https://doi.org/10.1016/j.phpro.2014.08.159 VL - 56 SP - 167 EP - 175 PB - Elsevier ER - TY - CHAP A1 - Amend, Philipp A1 - Mrotzek, Tino A1 - Laumer, Tobias A1 - Wolf, Michel A1 - Roth, Stephan A1 - Gude, Maik A1 - Schmidt, Michael T1 - Experimental Investigations on Laser-based Hot-melt Bonding and Injection Molding for Laser-structured Metal Plastic Hybrids T2 - Laser in Manufacturing (LIM 2017), Munich, Germany N2 - The use of thermoplastics in lightweight construction is continuing to grow. This implies the need for suitable joining techniques to combine thermoplastics with other materials, such as metals, to gain tailored multi-material parts. In this paper latest results of experimental investigations on laser-based hot-melt bonding and injection molding for laser-structured metal plastic hybrids are presented. As materials stainless steel and short-fiber reinforced polyamide are used. The stainless steel surface is structured with a nanosecond pulse laser before joining to improve the mechanical adhesion between the dissimilar materials. Thereby, different structure depths in the range between 16.6 ± 1.2 µm and 66.5 ± 2.5 µm as well as different hatch distances between 70 and 300 µm are realized. The laser-based joining process is carried out irradiating the metallic surface multiple times. Positioned below the metal in T-joint configuration, the thermoplastic melts as a result of heat transfer and acts as hot-melt cohesive. Besides, hybrid joints are manufactured using injection molding. For experiments, the mold temperature as well as the melt temperature are varied. Regardless of the joining process, the hybrid joints are mechanically characterized by tensile tests. The results demonstrate that for both joining processes strong laser-structured metal plastic hybrids can be realized. KW - injection molding KW - laser structuring KW - Laser-based hot-melt bonding KW - multi-material design Y1 - 2017 UR - https://www.researchgate.net/publication/318110636_Experimental_Investigations_on_Laser-based_Hot-melt_Bonding_and_Injection_Molding_for_Laser-structured_Metal_Plastic_Hybrids SN - 978-3-87525-428-0 ER - TY - CHAP A1 - Amend, Philipp A1 - Laumer, Tobias A1 - Roth, Stephan A1 - Baat, Florian A1 - Schmidt, Michael T1 - Investigations on Laser-based Hot-melt Bonding of Additive Manufactured Plastic Parts to Metal Sheets for Strong and Tight Multi-material Joints T2 - Laser in Manufacturing (LIM 2017), Munich, Germany N2 - In this paper, first results regarding the realization of laser-based hot-melt bonding of additive manufactured plastics parts to metal sheets for strong and tight multi-material joints are presented. Compared to earlier investigations, in which nearly solely extruded plastic materials were applied, the use of additive manufactured plastics complements the research field with a promising approach. Besides the typical advantages of multi-material joints regarding weight reduction and high strengths, such parts can meet the needs of constructional freedom and the avoiding of tool costs. Materials used for this paper are aluminum (AlMg3), stainless steel (1.4301) and polyamide 12 (PA12). The performed experiments resulting in multi-material joints between metal and polyamide. The realized specimens undergo a tensile shear test and a tightness test, in which the characteristics of the joints are determined. KW - additive manufacturing KW - Laser-based hot-melt bonding KW - multi-material joint Y1 - 2017 UR - https://www.researchgate.net/publication/318110485_Investigations_on_Laser-based_Hot-melt_Bonding_of_Additive_Manufactured_Plastic_Parts_to_Metal_Sheets_for_Strong_and_Tight_Multi-material_Joint ER - TY - JOUR A1 - Stichel, Thomas A1 - Geißler, Bastian A1 - Jander, Julius A1 - Laumer, Tobias A1 - Frick, Thomas A1 - Roth, Stephan T1 - Electrophotographic multi-material powder deposition for additive manufacturing JF - Journal of Laser Applications N2 - In this paper, the use of electrophotographic polymer powder transfer for the preparation of multi-material layers is discussed with respect to the application in powder bed-based additive manufacturing technologies as selective laser sintering (SLS). Therefore, the challenges of this task are considered verifying the critical process steps in order to develop a concept for an electrophotograhic laser sintering machine. On that basis, an experimental setup with a two-chamber design is realized which enables the investigation of the electrophotographic powder transfer at typical process conditions of SLS. Using this setup, transfer tests of polypropylene powder patterns were performed and qualitatively analyzed by photographic imaging. The results confirm the high potential of the application of electrophotography for multi-material powder deposition and show how a residual electrophotographic powder deposition can be achieved in general, which is independent from the already produced part height, in order to build up three-dimensional multi-material components. Y1 - 2018 U6 - https://doi.org/10.2351/1.5040619 VL - 30 IS - 3 PB - AIP Publishing ER - TY - BOOK A1 - Weilkiens, Tim A1 - Huwaldt, Alexander A1 - Mottok, Jürgen A1 - Roth, Stephan A1 - Willert, Andreas T1 - Modellbasierte Softwareentwicklung für eingebettete Systeme verstehen und anwenden N2 - Die Beherrschung von Komplexität ist eine der größten Engineering-Herausforderungen des 21. Jahrhunderts. Themen wie das „Internet der Dinge“ (IoT) und „Industrie 4.0“ beschleunigen diesen Trend. Die modellgetriebene Entwicklung leistet einen entscheidenden Beitrag, um diesen Herausforderungen erfolgreich begegnen zu können. Die Autoren geben einen fundierten Einstieg und praxisorientierten Überblick über die Modellierung von Software für eingebettete Systeme von den Anforderungen über die Architektur bis zum Design, der Codegenerierung und dem Testen. Für jede Phase werden Paradigmen, Methoden, Techniken und Werkzeuge beschrieben und ihre praktische Anwendung in den Vordergrund gestellt. Darüber hinaus wird auf die Integration von Werkzeugen, funktionale Sicherheit und Metamodellierung eingegangen sowie die Einführung eines modellbasierten Ansatzes in einer Organisation und die Notwendigkeit zum lebenslangen Lernen erläutert. Der Leser erfährt in diesem Buch, wie ein modellbasiertes Vorgehen nutzbringend in der Praxis für die Softwareentwicklung eingesetzt wird. Das Vorgehen wird unabhängig von Modellierungswerkzeugen vorgestellt. Zahlreiche Beispiele – exemplarisch auch auf Basis konkreter Werkzeuge – helfen bei der praktischen Umsetzung. Y1 - 2018 SN - 978-3-86490-524-7 PB - dpunkt.Verlag CY - Heidelberg ER -