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 - 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 - 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 - 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 - 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 -