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 - 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 - 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 -