TY - JOUR A1 - Laumer, Tobias A1 - Stichel, Thomas A1 - Riedlbauer, Daniel A1 - Amend, Philipp A1 - Mergheim, Julia A1 - Schmidt, Michael T1 - Realization of multi-material polymer parts by simultaneous laser beam melting JF - Journal of Laser Micro / Nanoengineering 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 UR - https://www.researchgate.net/publication/274250254_Realization_of_multi-material_polymer_parts_by_simultaneous_laser_beam_melting VL - 10 IS - 2 PB - Japan Laser Processing Society ER - TY - JOUR A1 - Laumer, Tobias A1 - Stichel, Thomas A1 - Amend, Philipp A1 - Schmidt, Michael T1 - Simultaneous laser beam melting of multimaterial polymer parts JF - Journal of Laser Applications N2 - By simultaneous laser beam melting (SLBM), parts consisting of different polymer powders can be additively manufactured within one building process. Besides the advantages of conventional LBM, e.g., not needing additional tools and being able to realize parts with almost any geometry, different product requirements can be achieved within a single part. Product requirements may be different chemical resistances or haptic material properties. Therefore, SLBM enlarges the application field for additive manufacturing in general. In the process, two different materials are deposited on the building platform and preheated a few degrees below the melting temperature of the lower melting polymer by infrared emitters. Afterward, a CO2 laser (λ = 10.6 μm) provides the energy for the temperature difference between the preheating temperatures of both materials. Finally, a digital light processing chip is used to achieve simultaneous and flexible energy deposition for melting both preheated polymers. By illuminating the chip with a laser, parts of the beam can be flexibly guided onto the powder bed or into a beam trap. As laser, a single mode thulium laser (λ = 1.94 μm) is used. After melting the layer, a new layer is deposited and the process starts anew. In this paper, polypropylene and polyamide 12 are used as materials. After analyzing the material and melting behavior during the process by a high-resolution thermal imaging system, the parts are qualified regarding their material compatibility at the boundary zone and porosity by cross sections. KW - additive manufacturing KW - material qualification KW - Multi-Material Parts KW - new processes Y1 - 2015 U6 - https://doi.org/10.2351/1.4906303 SN - 1938-1387 SN - 1042-346X VL - 27 IS - S2 PB - Laser Institute of America 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 - Laumer, Tobias A1 - Stichel, Thomas A1 - Bock, Thomas A1 - Amend, Philipp A1 - Schmidt, Michael T1 - Characterization of temperature-dependent optical material properties of polymer powders T2 - AIP Conference Proceedings N2 - 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. KW - laser beam melting KW - material qualification KW - Optical Material Properties KW - Polymers Y1 - 2014 U6 - https://doi.org/10.1063/1.4918508 IS - 1 PB - AIP Publishing 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 - 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 - 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 - 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 -