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 - Stichel, Thomas A1 - Laumer, Tobias A1 - Amend, Philipp A1 - Wittmann, Peter T1 - Selective deposition of polymer powder by vibrating nozzles for laser beam melting T2 - Proceedings of Laser in Manfacturing Conference 2015, June 22, 2015 - June 25, 2015, Munich, Germany N2 - In this report, the delivery of polyamide 12 (PA 12) powder and powder layer preparation by vibrating steel nozzles is investigated and discussed with respect to its application for laser beam melting. Therefore, a setup was realized which includes a steel nozzle attached to a piezo actor as well as a positioning system. In order t o investigate the mass flow characteristics in dependency on the applied vibration state, a weighing cell is used enabling time-resolved mass flow measurements. Moreover, single-layer patterns consisting of colored and uncolored polyamide 12 were created and characterized regarding surface homogeneity and selectivity before as well as after the melting of the powder layers by a hot plate. KW - laser beam melting KW - multi-material KW - polyamide 12 KW - vibrating nozzle Y1 - 2015 UR - https://www.wlt.de/lim/Proceedings/Stick/PDF/Contribution241_final.pdf 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 - Osmanlic, Fuad A1 - Wudy, Katrin A1 - Laumer, Tobias A1 - Schmidt, Michael A1 - Drummer, Dietmar A1 - Körner, Carolin T1 - Modeling of Laser Beam Absorption in a Polymer Powder Bed JF - Polymers N2 - In order to understand the absorption characteristic, a ray trace model is developed by taking into account the reflection, absorption and refraction. The ray paths are resolved on a sub-powder grid. For validation, the simulation results are compared to analytic solutions of the irradiation of the laser beam onto a plain surface. In addition, the absorptance, reflectance and transmittance of PA12 powder layers measured by an integration sphere setup are compared with the numerical results of our model. It is shown that the effective penetration depth can be lower than the penetration depth in bulk material for polymer powders and, therefore, can increase the energy density at the powder bed surface. The implications for modeling of the selective laser sintering (SLS) process and the processability of fine powder distributions and high powder bed densities are discussed. KW - additive manufacturing KW - laser absorption KW - PA12 KW - polyamide 12 KW - powder bed Y1 - 2018 U6 - https://doi.org/10.3390/polym10070784 VL - 10 IS - 7 SP - 1 EP - 11 PB - MDPI ER -