TY - JOUR A1 - Kuehn, Cornelius A1 - Mehl, Oliver A1 - Laumer, Tobias A1 - Witt, Gerd T1 - Comparison between the optical properties of injection molded and additive manufactured components JF - Procedia CIRP N2 - Fused Layer Manufacturing (FLM) is an additive technology based on polymer material extrusion. Due to variations in temperature during the manufacturing process and the resulting stress between the stacked layers, the final parts show anisotropic mechanical properties. One possible approach for their reduction is the immediate local preheating of the surface via laser radiation. At first, our research examines the influence of laser parameters as wavelength, power, velocity and area of impact for the preheating of the surface. In addition, an overview of possible parameter combinations is given based on the selection of raw materials, its colors, thicknesses and the manufacturing process. Initially, the absorption level of the materials regarding the emitted wavelength is detected using a spectrophotometer. Subsequently, preheating tests are conducted with different laser types while the temperature is determined by a thermal camera. The selected laser type is planned to get mounted on a prototype-machine for further in-situ preheating experiments on FLM parts during the manufacturing process. KW - additive manufacturing KW - FLM-Printing KW - injection molding KW - Laser assisted processes KW - Optical properties KW - Polymers KW - Preheating Y1 - 2018 U6 - https://doi.org/10.1016/j.procir.2018.08.106 VL - 74 SP - 259 EP - 263 PB - Elsevier ER - TY - JOUR A1 - Geißler, Bastian A1 - Laumer, Tobias A1 - Wübbeke, Andrea A1 - Frick, Thomas A1 - Schöppner, Volker A1 - Schmidt, Michael T1 - Analysis of the Weld Seam Morphology of Polypropylene in Laser Transmission Welding JF - Journal of Manufacturing Science and Engineering N2 - Laser transmission welding is a well-known joining technology for welding thermoplastics. Although the process is already used industrially, fundamental process-structure-property relationships are not fully understood and are therefore the subject of current research. One aspect of these mentioned process-structure-property relationships is the interaction between the temperature field during the welding process, the weld seam morphology of semi-crystalline thermoplastics, and the weld seam strength. In this study, the influence of the line energy on the weld seam morphology of polypropylenes is analyzed. For this purpose, the size of spherulites in the weld seam is investigated, as well as different occurring phases of polypropylene (a- and b-phase). It is shown that both the spherulite size of the a-phase and the amount of b-phase increase with increasing line energy. For the explanation and discussion of the results, a temperature-dependent thermal simulation model is used to derive characteristic attributes of the temperature field (maximum temperatures, cooling rates, temperature gradients). Y1 - 2018 U6 - https://doi.org/10.1115/1.4040876 VL - 140 IS - 11 PB - ASME ER - TY - JOUR A1 - Heinl, M. A1 - Laumer, Tobias A1 - Bayer, F. A1 - Hausotte, Tino T1 - Temperature-dependent optical material properties of polymer powders regarding in-situ measurement techniques in additive manufacturing JF - Polymer Testing N2 - Due to the growing number of applications for Additive Manufacturing (AM), an increasing need for enhanced quality control methods exists. Here optical measurement techniques are often used for in-situ monitoring in AM. There is a great potential to standardize and improve applications of optical measurement devices in accordance to the increasing requirements of measuring tasks. Beside the optical material qualifications, especially process-oriented changes in optical effects are of great relevance for in-situ evaluations. The optical modifications may be attributed to aggregate specific phase transitions coming along with variable emitted wavelengths. A measuring setup with two integrations spheres and a heated process chamber have been developed to analyze the optical interactions of laser radiation and visual illumination with the powder. The process oriented analysis for selective laser sintering lead to improved operating conditions in the field of in-situ measurements in combination with an accurate evaluation of the absorption ratio of the examined powder. Y1 - 2018 U6 - https://doi.org/10.1016/j.polymertesting.2018.09.016 VL - 71 IS - October SP - 378 EP - 383 PB - Elsevier ER - TY - THES A1 - Laumer, Tobias T1 - Erzeugung von thermoplastischen Werkstoffverbunden mittels simultanem, intensitätsselektivem Laserstrahlschmelzen N2 - Mittels des entwickelten additiven Fertigungsprozesses des simultanen, intensitätsselektiven Laserstrahlschmelzens lassen sich Werkstoffverbunde bestehend aus unterschiedlichen Polymerwerkstoffen mit hohen Bauteilfestigkeiten realisieren. Die zukünftig realisierbaren Werkstoffverbunde können dabei durch eine örtlich variable Ausnutzung der unterschiedlichen Werkstoffeigenschaften die hinsichtlich lokal definierter Belastungsprofile gestellten Anforderungen an komplexe Multi-Material-Bauteile erfüllen. Dadurch lassen sich neue Anwendungsfelder für die additive Fertigung von Werkstoffverbunden erschließen. Y1 - 2017 UR - https://www.researchgate.net/publication/330440080_Erzeugung_von_thermoplastischen_Werkstoffverbunden_mittels_simultanem_intensitatsselektivem_Laserstrahlschmelzen SN - 978-3-87525-428-0 PB - Meisenbach CY - Bamberg ER - TY - CHAP A1 - Schmidt, Jochen A1 - Fanselow, Stephanie A1 - Wirth, Karl-Ernst A1 - Peukert, Wolfgang A1 - Hiller, Saskia A1 - Laumer, Tobias A1 - Schmidt, Michael ED - Witt, Gerd ED - Wegner, Andreas ED - Sehrt, Jan T1 - Herstellung von Polyolefinstrahlschmelzmaterialien mittels Schmelzeemulgieren zum Einsatz in der additiven Fertigung T2 - Neue Entwicklungen in der Additiven Fertigung N2 - 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. Y1 - 2015 SN - 978-3-662-48472-2 U6 - https://doi.org/10.1007/978-3-662-48473-9_2 SP - 13 EP - 23 PB - Springer CY - Berlin, Heidelberg 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 - Laumer, Tobias T1 - The influence of micro-sized structures on the compound strength of multi-material components built by Simultaneous Laser Beam Melting of Polymers T2 - Proceedings of LPM2016 - the 17th International Symposium on Laser Precision Microfabrication, 2016, Xian, China N2 - Simultaneous laser beam melting (SLBM) allows the direct realization of multi-material components consisting of different polymer materials by a single Additive Manufacturing (AM) process. To achieve a high compound strength between different materials by adhesive bonding, a common boundary zone based on diffusion of the macromolecules is necessary and thus, both materials needs to be compatible regarding their specific adhesion compatibility. However, by SLBM also incompatible polymers can be processed to multi-material parts. If two incompatible polymers are processed, a positive locking between the different materials is necessary to achieve a connection between the materials. The positive locking results of a random mixture process of the different powder materials during the powder deposition process by a two chamber recoater system, which leads to the forming of undercuts of one material in the other during the melting and recrystallization. In this paper, thermoplastic elastomer (TPE) and polypropylene (PP) powders, which are incompatible, are processed to multi-material specimens. By qualifying basic material properties, their influence on the process and especially on the forming of undercuts in the boundary zone is analyzed. To also allow the analysis of the influence of both material and process parameters on the resulting part properties, tensile test specimens are built and their tensile strength is determined. Additionally, cross sections of the boundary zone are prepared and analyzed by microscope images. KW - 3D printing KW - additive manufacturing KW - multi-material parts KW - powder material qualification KW - selective laser beam melting of polymers Y1 - 2016 UR - https://www.researchgate.net/publication/304199990_The_influence_of_micro-sized_structures_on_the_compound_strength_of_multi-material_components_built_by_Simultaneous_Laser_Beam_Melting_of_Polymers ER - TY - JOUR A1 - Blümel, Christina A1 - Sachs, Marius A1 - Laumer, Tobias A1 - Winzer, Bettina A1 - Schmidt, Jochen A1 - Schmidt, Michael A1 - Peukert, Wolfgang A1 - Wirth, Karl-Ernst T1 - Increasing flowability and bulk density of PE-HD powders by a dry particle coating process and impact on LBM processes JF - Rapid Prototyping Journal N2 - Purpose – The purpose of this paper is to demonstrate the processability of cohesive PE-HD particles in laser beam melting processes (LBM) of polymers. Furthermore, we present a characterization method for polymer particles, which can predict the quality of the powder deposition via LBM processes. Design/methodology/approach – This study focuses on the application of dry particle coating processes to increase flowability and bulk density of PE-HD particles. Both has been measured and afterwards validated via powder deposition of PE-HD particles in a LBM machine. Findings – For efficient coating in a dry particle coating process, the PE-HD particles and the attached nanoparticles need to show similar surface chemistry, i.e. both need to behave either hydrophobic or hydrophilic. It is demonstrated that dry particle coating is appropriate to enhance flowability and bulk density of PE-HD particles and hence considerably improves LBM processes and the resulting product quality. Originality/value – At present, in LBM processes mainly polyamide (PA), 12 particles are used, which are so far quite expensive in comparison to, for example, PE-HD particles. This work provides a unique and versatile method for nanoparticulate surface modification which may be applied to a wide variety of materials. After the coating, the particles are applicable for the LBM process. Our results provide a correlation between flowability and bulk density and the resulting product quality. KW - Polymers KW - Bulk density KW - Dry particle coating KW - Flowability KW - Hydrophilic KW - Hydrophobic Y1 - 2015 U6 - https://doi.org/10.1108/RPJ-07-2013-0074 SN - 1758-7670 SN - 1355-2546 VL - 21 IS - 6 SP - 697 EP - 704 PB - Emerald ER - TY - CHAP A1 - Laumer, Tobias A1 - Karg, Michael Cornelius Hermann A1 - Schmidt, Michael T1 - Neue Prozessstrategien zur Herstellung von Multi- Material-Bauteilen und Gradientenwerkstoffen T2 - Zukunft individuell gestalten : Industriekolloquium des Sonderforschungsbereichs 814 - Additive Fertigung ; [Dezember 2012 ; Nürnberg] N2 - Das additive Fertigungsverfahren, dem gemeinhin die größten Potentiale zugesprochen werden, ist das Laserstrahlschmelzen im Pulverbett von Kunststoffen (LSS-K) und von Metallen (LSS-M). Wie bei anderen Techniken der additiven Fertigung werden Bauteile direkt aus CAD-Dateien ohne zusätzliche Werkzeuge bei enormer konstruktiver Freiheit gefertigt. Die resultierenden Werkstoffeigenschaften sind vergleichbar mit konventionelleren Prozessrouten wie etwa dem Spritzgießen thermoplastischer Polymere beziehungsweise auf der Seite der Metalle dem Schmieden oder Gießen. Derzeit wird der Einsatz des LSS zur Fertigung von Endprodukten in kleinen Stückzahlen erschwert von nicht ausreichender Prozessstabilität und, insbesondere bei Kunststoffen, von der eingeschränkten Werkstoffauswahl. Bisher werden für beide Werkstoffklassen Bauteile aus jeweils einem einzigen Ausgangsmaterial hergestellt. Näherungsweise erzeugt LSS also einheitliche Materialeigenschaften über das gesamte Bauteil hinweg. Ein Ansatz, der in den Teilprojekten A5 und B6 des Sonderforschungsbereichs 814 verfolgt wird, ist die Realisierung von Multi-Material-Bauteilen mittels LSS-K beziehungsweise LSS-M. Y1 - 2012 UR - https://www.researchgate.net/publication/338986395_Neue_Prozessstrategien_zur_Herstellung_von_Multi-_Material-Bauteilen_und_Gradientenwerkstoffen SP - 101 EP - 116 CY - Erlangen 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 - Laumer, Tobias T1 - Realization of Multi-material Polymer Parts by Simultaneous Laser Beam Melting JF - Journal of Laser Micro/Nanoengineering (JLMN) N2 - In this paper, first results regarding the realization of multi-material parts by Simultaneous Laser Beam Melting (SLBM) of polymers are presented. This new approach allows the layerwise generation of parts consisting of different polymer materials within one building process. Besides the typical advantages of additive manufacturing technologies, such parts can fulfill different product requirements concomitant and therefore could enlarge the overall field of application. The powder materials used for this paper are polyethylene (PE) and a polyamide based thermoplastic elastomer (TPE). After depositing the powder materials next to each other, infrared-emitters heat the lower melting polymer and a CO2 laser provides the preheating temperature of the higher melting polymer. In the last step, a thulium fibre laser melts the two preheated powders simultaneously.The realized specimens are characterized by cross sections and their tensile strengths are determined. Additionally, the new approach of the simultaneous energy irradiation is investigated using a Finite Element Analysis in order to gain a more profound process understanding. In that sense, the influence of the size of the exposure area on the reachable maximum temperatures inside that area was analyzed by the simulation and compared to experimental studies. KW - additive manufacturing KW - Multi-Material Parts KW - NewMaterials KW - Simultaneous Laser Beam Melting of Polymers Y1 - 2015 U6 - https://doi.org/10.2961/jlmn.2015.02.0006 VL - 10 IS - 2 SP - 140 EP - 147 PB - Japan Laser Processing Society ER - TY - CHAP A1 - Laumer, Tobias A1 - Karg, Michael Cornelius Hermann A1 - Schmidt, Michael T1 - Additive Manufacturing of Gradient and Multimaterial Components T2 - International Conference on Competitive Manufacturing COMA, 2013, Stellenbosch N2 - In the paper first results regarding the realisation of gradient and multi-material parts manufactured by Laser Beam Melting in powder bed of metals and polymers are published. Gradient properties of additively manufactured metal parts can be achieved by varying the composition of alloying components in the powder and adapting process strategies. As an alternative to atomizing pre-alloyed materials, mixtures of different powders are investigated. For realizing multi-material-parts from polymers, at first relevant material properties concerning compatibility have to be analysed. Therefore the paper shows the main requirements for compatibility between different materials and also first results regarding the compatibility of polymer powders and possible combinations for the manufacturing of multi-material components by laser beam melting of polymers. KW - additive manufacturing KW - Laser Beam Melting in Powder Bed KW - New Materials Y1 - 2013 UR - https://www.researchgate.net/publication/318723870_Additive_Manufacturing_of_Gradient_and_Multimaterial_Components ER - TY - CHAP A1 - Laumer, Tobias A1 - Karg, Michael Cornelius Hermann A1 - Schmidt, Michael T1 - Neue Prozessstrategien zur Herstellung von Multi-Material-Bauteilen mit Hilfe des Laserstrahlschmelzens T2 - Industriekolloquium des SFB 814, 2, 2013, Nürnberg Y1 - 2013 UR - https://www.researchgate.net/publication/295861222_Neue_Prozessstrategien_zur_Herstellung_von_Multi-Material-Bauteilen_mit_Hilfe_des_Laserstrahlschmelzens SN - 978-3-931864-59-0 PB - Universität Erlangen-Nürnberg, Lehrstuhl für Kunststofftechnik 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 - JOUR A1 - Kuettner, Andreas A1 - Raths, Max A1 - Fischer, Samuel A1 - Laumer, Tobias T1 - Heat staking of polymer parts generated by fused layer modeling JF - The International Journal of Advanced Manufacturing Technology N2 - 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. KW - Heat staking KW - Additive manufacturing KW - 3D printing KW - Material qualification KW - Polycarbonate (PC) KW - Fused layer modeling (FLM) Y1 - 2023 U6 - https://doi.org/10.1007/s00170-023-11850-y VL - 128 SP - 547 EP - 562 PB - Springer Nature ER - TY - JOUR A1 - Raths, Max A1 - Bauer, Lukas A1 - Kuettner, Andreas A1 - Fischer, Samuel A1 - Laumer, Tobias T1 - Gradual error detection technique for non-destructive assessment of density and tensile strength in fused filament fabrication processes JF - The International Journal of Advanced Manufacturing Technology N2 - Fused filament fabrication (FFF) is a widely used additive manufacturing process for producing functional components and prototypes. The FFF process involves depositing melted material layer-by-layer to build up 3D physical parts. The quality of the final product depends on several factors, including the component density and tensile strength, which are typically determined through destructive testing methods. X-ray microtomography (XCT) can be used to investigate the pore sizes and distribution. These approaches are time-consuming, costly, and wasteful, making it unsuitable for high-volume manufacturing. In this paper, a new method for non-destructive determination of component density and estimation of the tensile strength in FFF processes is proposed. This method involves the use of gradual error detection by sensors and convolutional neural networks. To validate this approach, a series of experiments has been conducted. Component density and tensile strength of the printed specimens with varying extrusion factor were measured using traditional destructive testing methods and XCT. The cumulative error detection method was used to predict the same properties without destroying the specimens. The predicted values were then compared with the measured values, and it was observed that the method accurately predicted the component density and tensile strength of the tested parts. This approach has several advantages over traditional destructive testing methods. The method is faster, cheaper, and more environmentally friendly since it does not require the destruction of the product. Moreover, it facilitates the testing of each individual part instead of assuming the same properties for components from one series. Additionally, it can provide real-time feedback on the quality of the product during the manufacturing process, allowing for adjustments to be made as needed. The advancement of this approach points toward a future trend in non-destructive testing methodologies, potentially revolutionizing quality assurance processes not only for consumer goods but various industries such as electronics or automotive industry. Moreover, its broader applications extend beyond FFF to encompass other additive manufacturing techniques such as selective laser sintering (SLS), or electron beam melting (EBM). A comparison between the old destructive testing methods and this innovative non-destructive approach underscores the possible fundamental change toward more efficient and sustainable manufacturing practices. This approach has the potential to significantly reduce the time and cost associated with traditional destructive testing methods while ensuring the quality of FFF-manufactured products. KW - Error detection KW - Additive manufacturing KW - Fused filament fabrication KW - Artificial neural network KW - Image processing KW - Porosity Y1 - 2024 U6 - https://doi.org/10.1007/s00170-024-13280-w SN - 1433-3015 SN - 0268-3768 N1 - Open Access funding enabled and organized by Projekt DEAL. IS - 131 SP - 4149 EP - 4163 PB - Springer CY - London ER - TY - CHAP A1 - Laumer, Tobias A1 - Stichel, Thomas A1 - Amend, Philipp A1 - Schmidt, Michael A1 - Gachot, A. T1 - Simultaneous Energy Deposition for Laser Beam Melting of Polymers T2 - Proceedings of the Polymer Processing Society 29th Annual Meeting, Nürnberg, 2013 Y1 - 2013 PB - American Institute of Physics CY - New York ER - TY - JOUR A1 - Stichel, Thomas A1 - Frick, Thomas A1 - Laumer, Tobias A1 - Tenner, Felix A1 - Hausotte, Tino A1 - Merklein, Marion A1 - Schmidt, Michael T1 - A Round Robin study for Selective Laser Sintering of polyamide 12: Microstructural origin of the mechanical properties JF - Optics & Laser Technology N2 - The mechanical and microstructural investigation of polymer parts (polyamide 12) fabricated by Selective Laser Sintering as part of a Round Robin initiative is presented. The paper focuses on the microstructural analysis of the Round Robin samples and their evaluation regarding their effect on mechanical properties with respect to each other. Therefore optical microscopy on microtomed samples, X-ray computed tomography and Differential Scanning Calorimetry is used to determine the morphology of residual particle cores and of internal pores. Y1 - 2017 U6 - https://doi.org/10.1016/j.optlastec.2016.09.042 VL - 89 SP - 31 EP - 40 PB - Elsevier ER - TY - JOUR A1 - Launhardt, M. A1 - Wörz, A. A1 - Loderer, A. A1 - Laumer, Tobias A1 - Drummer, Dietmar A1 - Hausotte, Tino A1 - Schmidt, Michael T1 - Detecting surface roughness on SLS parts with various measuring techniques JF - Polymer Testing N2 - Selective Laser Sintering (SLS) is an additive manufacturing technique whereby a laser melts polymer powder layer by layer to generate three-dimensional parts. It enables the fabrication of parts with high degrees of complexity, nearly no geometrical restrictions, and without the necessity of a tool or a mold. Due to the orientation in the building space, the processing parameters, and the powder properties, the resulting parts possess an increased surface roughness. In comparison to other manufacturing techniques, e.g. injection molding, the surface roughness of SLS parts results from partially melted powder particles on the surface layer. The actual surface roughness must thus be characterized with respect to the part's eventual application. At the moment, there is no knowledge regarding which measuring technique is most suitable for detecting and quantifying SLS parts' surface roughness. The scope of this paper is to compare tactile profile measurement methods, as established in industry, to optical measurement techniques such as Focus Variation, Fringe Projection Technique (FPT), and Confocal Laser Scanning Microscope (CLSM). The advantages and disadvantages of each method are presented and, additionally, the effect of tactile measurement on a part's surface is investigated. KW - Selective Laser Sintering (SLS) KW - PA12 KW - Surface roughness KW - Measuring technique Y1 - 2016 SN - 0142-9418 U6 - https://doi.org/10.1016/j.polymertesting.2016.05.022 SN - 1873-2348 VL - 53 SP - 217 EP - 226 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Hupfeld, T. A1 - Laumer, Tobias A1 - Stichel, T. A1 - Schuffenhauer, T. A1 - Heberle, J. A1 - Schmidt, Michael A1 - Barcikowski, S. A1 - Gökce, B. T1 - A new approach to coat PA12 powders with laser-generated nanoparticles for selective laser sintering JF - Procedia CIRP N2 - The modification of selective laser sintering (SLS) powder materials by nanoadditives offers the possibility to adapt the powder properties to the laser sintering process or the resulting part properties. To avoid agglomeration of the nanofiller, a new approach in which surfactant-free laser-generated colloidal nanoparticles are adsorbed onto the polymer surface directly in an aqueous solution is demonstrated. Based on this novel approach, polyamide 12 (PA12) powders are decorated with metal and oxide nanoparticles and processed via SLS. Electron microscopy and confocal laser scanning imaging are utilized to analyze the dispersion of the filler. KW - laser additive manufacturing KW - nanoparticles KW - polymer powders KW - pulsed laser ablation in liquids KW - selective laser sintering Y1 - 2018 U6 - https://doi.org/10.1016/j.procir.2018.08.103 VL - 74 SP - 244 EP - 248 PB - Elsevier ER - TY - JOUR A1 - Laumer, Tobias A1 - Stichel, T. A1 - Nagulin, K. A1 - Schmidt, Michael T1 - Optical analysis of polymer powder materials for Selective Laser Sintering JF - Polymer Testing N2 - This study increases the basic understanding of optical material properties of polymer powders used in selective laser sintering (SLS). Therefore, different polymer powder materials were analyzed regarding their optical material properties with an integration spheres measurement setup. By the measurements a direct connection between the absorption behavior of the solid material and the overall optical material characteristics of the same material in powdery form could be shown. The results were used to develop an advanced explanation model for the optical material properties of powders. At present, existing explanation models only consider the occurring of multiple reflections in the gaps between the particles to explain the overall optical material properties of powder materials. Thus, by also considering the absorption behavior of the single particles, the basic understanding of the beam-matter interaction and their effect on the optical material properties of powder materials can be expanded. KW - Additive manufacturing KW - Selective Laser Sintering KW - Optical material characteristics KW - Integration spheres KW - Material qualification KW - New materials Y1 - 2016 U6 - https://doi.org/10.1016/j.polymertesting.2016.10.010 SN - 1873-2348 SN - 0142-9418 VL - 56 SP - 207 EP - 213 PB - Elsevier Science CY - Amsterdam [u.a.] ER - TY - JOUR A1 - Stichel, T. A1 - Raths, Max A1 - Laumer, Tobias A1 - Roth, Stephan T1 - Multi-Material Deposition of Polymer Powders with Vibrating Nozzles for a New Approach of Laser Sintering JF - Journal of Laser Micro/Nanoengineering (JLMN) N2 - Conventional Selective Laser Sintering of polymers is restricted to the processing of single materials. The fabrication of components consisting of different material regions is a challenge which cannot be realized by standard coating devices basing on blades or rollers. Thus, advanced coating and deposition techniques are needed which enable the precise and reliable control over very small powder quantities in order to prepare arbitrary powder patterns with high accuracy and repeatability. In this report, the delivery of polymer powder by vibrating nozzles inside laser sintering machines is investigated. Therefore, a steel nozzle attached to a piezo actuator is integrated into a machine, whereas the nozzle itself features internal channels which allow the precise control over the powder temperature using heat transfer oil. The setup is used to study the influence of different system configurations on the powder deposition characteristics as resolution and layer surface roughness. The results show that temperature influences the mass flow depending on the material used and that a precise deposition of powder pattern with microscale resolution is possible with optimized parameters. Finally, the multimaterial powder pattern is fused by a new illumination strategy of laser sintering which is called Simultaneous Intensity-Selective Laser Sintering in order to demonstrate the potential of this new approach. Y1 - 2018 U6 - https://doi.org/10.2961/jlmn.2018.02.0002 VL - 13 IS - 2 SP - 55 EP - 62 PB - JLPS-Japan Laser Processing Society ER - TY - CHAP A1 - Laumer, Tobias A1 - Stichel, T. A1 - Sachs, Marius A1 - Amend, Philipp A1 - Schmidt, Michael ED - Bártolo, Paulo T1 - Qualification and modification of new polymer powders for laser beam melting using Ulbricht spheres T2 - High value manufacturing : Advanced research in virtual and rapid prototyping ; Proceedings of the 6th International Conference on Advanced Research and Rapid Prototyping, Leiraia, Portugal, 1-5 October, 2013 N2 - The restricted amount of available materials for Laser Beam Melting (LBM) of polymers is one of the main limitations for expanding the technology. Current qualification methods deal with problems like inadequate powder flowability or high part porosities among others but do not offer a detailed analysis of the important beam-matter-interaction between powder particles and electro-magnetic laser radiation. In this paper, polyethylene powder is qualified for the LBM process and specifically analyzed regarding the optical material properties of the powder for a wavelength of 10.6 μm. By admixing graphite as absorption intensifier the change of the optical material properties and the thereby connected processing parameters are analyzed. Furthermore an explanation approach is given to explain the relation between different transmittances of different powder particles and the optical material properties of the polymer powders. Y1 - 2014 UR - https://www.researchgate.net/publication/286311000_Qualification_and_modification_of_new_polymer_powders_for_laser_beam_melting_using_Ulbricht_spheres SN - 978-1-138-00137-4 SN - 1138001376 SP - 255 EP - 260 PB - CRC Press CY - Boca Raton ER - TY - JOUR A1 - Kuettner, Andreas A1 - Fischer, Samuel A1 - Laumer, Tobias T1 - Mechanical and structural characterization of heat-staked parts realized by selective laser sintering of polyamide 12 JF - The International Journal of Advanced Manufacturing Technology N2 - Heat staking is a joining process in which thermoplastic pins are formed by heat and pressure in a form-fitting and insoluble way. This study evaluates the mechanical performance and microstructure of selective laser sintered (SLS) polyamide 12 (PA 12) components before and after heat staking, compared with conventionally turned reference specimens. The components were characterized using tensile tests, micrographs, microscopy, and micro-CT measurements. For the tests, the forces and temperatures during heat staking were varied to determine the best process parameters. Tensile tests revealed that SLS joints achieved strengths of up to 33.6 MPa, approaching the 39.9 MPa of the turned references. Microstructural analysis showed a marked reduction in porosity due to heat staking. Porosity decreased from 3.9% to 1.56% at a staking force of 300 N and from 4.29% to 0.81% at 1000 N, highlighting the beneficial effect of increased force. These results demonstrate that heat staking parameters significantly influence local densification and mechanical performance, and that, under suitable conditions, SLS components can achieve joint strengths comparable to conventionally manufactured parts. The study shows that the heat staking process parameters have a significant influence on the local microstructure and thus on the mechanical performance and provides a basis for optimizing SLS components for new heat staking applications. KW - Additive manufacturing KW - Heat staking KW - Material qualification KW - Polyamid 12 (PA) KW - Selective laser sintering (SLS) Y1 - 2026 U6 - https://doi.org/10.1007/s00170-025-17319-4 PB - Springer ER -