@inproceedings{22202, abstract = {{Structural parts for aviation have very high demands on the development and production process. Therefore, the entire process must be considered in order to produce high-quality AM metal parts. In this case study, a conventional part was selected to be optimized for AM. The process presented includes component selection, design improvement with a novel approach for topology optimization based on the AMendate algorithm as basis of MSC Apex Generative Design,component production on a SLM 250 HL and post-processing including heat treatment and surface smoothing. With the topology optimization a weight reduction of ~60 % could be realized, whereby the stress distribution is more homogeneous. Furthermore, the challenges of support optimization and post-processing have to be addressed, in order to produce competitive parts.}}, author = {{Klippstein, Sven Helge and Duchting, Anne and Reiher, Thomas and Hengsbach, F. and Menge, Dennis and Schmid, Hans-Joachim}}, booktitle = {{30th Annual International Solid Freeform Fabrication Symposium}}, pages = {{1932--1945}}, title = {{{Devolopment, Production and post-processing of a topology optimized aircraft bracket }}}, volume = {{30}}, year = {{2019}}, } @inproceedings{22183, abstract = {{Function integration is a key issue for an efficient and economic usage of Additive Manufacturing. An efficient heat transfer by topology optimized structures is a rarely considered approach which will be outlined with an exemplary electronic housing which has been newly designed. A commercial projector unit, whose electrical components in total produce 38 W, shall be integrated in the closed housing and passively cooled by natural convection. Topology optimized structures shall be generated in the inner part of the housing to transfer the heat homogenously from the projector components to the housing wall while simultaneously minimizing the mass. At the outside of the housing walls, lattice and rib structures are applied to increase the effective surface for heat transfer by natural convection and radiation. Furthermore, the housing geometry is optimized regarding a minimization of support structures to reduce the post-processing effort. Finally, the housing shall be built of AlSi10Mg by SLM.}}, author = {{Menge, Dennis and Delfs, Patrick and Töws, Marcel and Schmid, Hans-Joachim}}, booktitle = {{29th Annual International Solid Freeform Fabrication Symposium}}, pages = {{687--697}}, title = {{{Topology Optimized Heat Transfer Using the Example of an Electronic Housing}}}, volume = {{29}}, year = {{2018}}, } @article{22196, abstract = {{The influence of selective laser sintering (SLS) parameters on PA12 part properties is well known, but research on other materials is rare. One alternative material is a thermoplastic elastomer (TPE) called PrimePart ST that is more elastic and shows a distinct SLS processing behavior. It undergoes a three-dimensional temperature distribution during the SLS process within the TPE part cake. To examine this further, a temperature measurement system that allows temperature measurements inside the part cake is applied to TPE in the present work. Position-dependent temperature histories are directly correlated with the color and mechanical properties of built parts and are in very good agreement with artificial heat treatment in a furnace. Furthermore, it is clearly shown that the yellowish discoloration of parts in different intensities is not only temperature dependent but also influenced by the residual oxygen content in the process atmosphere. Nevertheless, the discoloration has no influence on the mechanical part properties.}}, author = {{Kummert, Christina and Josupeit, Stefan and Schmid, Hans-Joachim}}, journal = {{Journal of Minerals, Metals and Materials Society}}, number = {{3}}, pages = {{425--430}}, publisher = {{Springer}}, title = {{{Thermoplastic Elastomer Part Color as Function of Temperature Histories and Oxygen Atmosphere During Selective Laser Sinterung}}}, doi = {{10.1007/s11837-017-2658-2}}, volume = {{70}}, year = {{2018}}, } @misc{29824, abstract = {{ Zusammenfassung: Bei einem Verfahren und einer Vor- richtung zur Bestimmung von Nanopartikeleigenschaften ei- nes nanopartikelbeladenen Aerosols (17), mit einer Test- kammer (1) zur Bestimmung der Nanopartikeleigenschaften des Aerosols (17), wobei die Testkammer (1) einen Aero- soleinlass (9) zum Einleiten des Aerosols (17) und ein Hül- lenluftstromeinlass (10) zur Einleitung eines Hüllenluftstroms (16) aufweist, die Oberseite (2) und die Unterseite (3) der Testkammer (1) jeweils eine flächige Elektrode (4, 5) auf- weist, so dass zwei im Abstand zueinander angeordnete Elektroden (4, 5) bereitstehen, zwischen denen ein elektri- sches Feld (6) erzeugbar ist, soll ein kompaktes Messgerät für die Vermessung der Eigenschaften von Aerosolnanopar- tikeln zur Verfügung gestellt werden, bei dem es ermöglicht wird, im selben Gerät die zweidimensionale Verteilung be- züglich des aerodynamischen und des volumenäquivalen- ten Durchmessers zu bestimmen, wodurch eine Lösung ge- schaffen wird, die es ermöglicht Aussagen über die Größe, die Masse, die Form und die geometrische Struktur einer Partikel zu treffen. Dies wird dadurch erreicht, dass der Inhalt der Testkammer (1) in Rotation versetzt wird, wobei die Ro- tationsachse (18) parallel zum elektrischen Feld (6) verläuft.}}, author = {{Schmid, Hans-Joachim and Rasche, David}}, title = {{{Bestimmung von Nanopartikeleigenschaften eines Aerosols}}}, year = {{2018}}, } @phdthesis{42128, author = {{Pieper, Sven}}, isbn = {{978-3-8440-5879-6}}, pages = {{135}}, publisher = {{Shaker Verlag}}, title = {{{Confinement Induced Segregation Effects in Suspension Rheology}}}, volume = {{5}}, year = {{2018}}, } @phdthesis{42130, author = {{Grimm, Philipp}}, pages = {{201}}, title = {{{Entwicklung einer Prozesskette zum flüssig-flüssig Phasentransfer nanoskaliger Partikeln}}}, year = {{2018}}, } @phdthesis{42131, author = {{Dörmann, Michael}}, pages = {{175}}, title = {{{Zur Modellierung von Kapillarbrücken zwischen nanoskaligen Partikeln}}}, year = {{2018}}, } @inbook{23759, author = {{Menge, Dennis and Josupeit, Stefan and Delfs, Patrick and Schmid, Hans-Joachim}}, booktitle = {{Additive Fertigung von Bauteilen und Strukturen}}, editor = {{Richard, Hans Albert and Schramm, Britta and Zipsner, Thomas}}, isbn = {{9783658177799}}, pages = {{105--120}}, publisher = {{Springer Vieweg}}, title = {{{Herstellbarkeit und mechanische Charakterisierung von lasergesinterten Gitterstrukturen}}}, doi = {{10.1007/978-3-658-17780-5}}, year = {{2017}}, } @article{22195, abstract = {{Polymer laser sintering (LS) is an important additive manufacturing (AM) technology. Individual and complex parts are directly produced from CAD data without the need of specific tools. The raw material is a polymer powder, which is deposited layerwise and melted selectively with a laser. Built parts are embedded in residual unmolten powder, the so-called part cake, which undergoes thermal ageing effects due to the exposure to high temperatures for long times during the manufacturing process. Hence, the recyclability of the unmolten powder is limited. This article focuses on a fundamental analysis of the ageing kinetics dependent on time, temperature, and oxygen content in the gas atmosphere. A model is developed and applied to measured, position-dependent process temperature histories to successfully predict the ageing distribution within a part cake. The results can be used to optimize the thermal process management in LS and to develop new efficient powder recycling methods. }}, author = {{Josupeit, Stefan and Schmid, Hans-Joachim}}, journal = {{Journal of Applied Polymer Science}}, number = {{42}}, publisher = {{Wiley}}, title = {{{Experimental analysis and modeling of local ageing effects during laser sintering of polyamide 12 in regard to individual thermal histories}}}, doi = {{10.1002/app.45435}}, volume = {{134}}, year = {{2017}}, } @inproceedings{22421, author = {{Lieneke, Tobias and Adam, Guido and Josupeit, Stefan and Delfs, Patrick and Zimmer, Detmar}}, booktitle = {{Proceedings of the 14th Rapid.Tech Conference}}, isbn = {{978-3-446-45460-6}}, pages = {{327--344}}, publisher = {{Hanser Verlag}}, title = {{{Maßtoleranzen für die additive Fertigung: Experimentelle Untersuchungen für das Lasersintern}}}, doi = {{10.3139/9783446454606.024 }}, year = {{2017}}, } @phdthesis{21950, author = {{Jesinghausen, Steffen}}, isbn = {{ 978-3-8440-5600-6}}, pages = {{182}}, publisher = {{Shaker}}, title = {{{Rheo-PIV nichtkolloidaler Suspensionen: Strukturelle Untersuchungen der Strömungsentwicklung in Schlitzdüsen mit Fokus auf Wandgleiten}}}, volume = {{3}}, year = {{2017}}, } @inproceedings{22180, abstract = {{The implementation of lattice structures into additive manufactured parts is an important method to decrease part weight maintaining a high specific payload. However, the manufacturability of lattice structures and mechanical properties for polymer laser sintering are quite unknown yet. To examine the manufacturability, sandwich structures with different cell types, cell sizes and lattice bar widths were designed, manufactured and evaluated. A decisive criterion is for example a sufficient powder removal. In a second step, manufacturable structures were analyzed using four-point-bending tests. Experimental data is compared to the density of the lattice structures and allows for a direct comparison of different cell types with varied geometrical attributes. The results of this work are guidelines for the design and dimensioning of laser sintered lattice structures.}}, author = {{Josupeit, Stefan and Delfs, Patrick and Menge, Dennis and Schmid, Hans-Joachim}}, booktitle = {{27th Annual International Solid Freeform Fabrication Symposium }}, pages = {{2077--2086}}, title = {{{Manufacturability and Mechanical Characterization of Laser Sintered Lattice Structures}}}, doi = {{http://utw10945.utweb.utexas.edu/sites/default/files/2016/166-Josupeit.pdf}}, volume = {{27}}, year = {{2016}}, } @article{22185, abstract = {{The layered structure of Additive Manufacturing processes results in a stair- stepping effect of the surface topographies. In general, the impact of this effect strongly depends on the build angle of a surface, whereas the overall surface roughness is additionally caused by the resolution of the specific AM process. The aim of this work is the prediction of the surface quality in dependence of the building orientation of a part. These results can finally be used to optimize the orientation to get a desired surface quality. As not all parts of the component surface are equally important, a preselection of areas can be used to improve the overall surface quality of relevant areas. The model uses the digital AMF format of a part. Each triangle is assigned with a roughness value and by testing different orientations the best one can be found. This approach needs a database for the surface qualities. This must be done separately for each Additive Manufacturing process and is shown exemplarily with a surface topography simulation for the laser sintering process.}}, author = {{Delfs, Patrick and Tows, Marcel and Schmid, Hans-Joachim}}, isbn = {{2214-8604}}, journal = {{Additive Manufacturing}}, number = {{12, Part B}}, pages = {{214--320}}, publisher = {{Elsevier}}, title = {{{Optimized build orientation of additive manufactured parts for improved surface quality and build time}}}, doi = {{10.1016/j.addma.2016.06.003}}, volume = {{2}}, year = {{2016}}, } @inproceedings{22190, author = {{Delfs, Patrick and Schmid, Hans-Joachim}}, booktitle = {{Fraunhofer Direct Digital Manufacturing Conference}}, isbn = {{978-3-8396-1001-5}}, pages = {{411--414}}, title = {{{Extended Analysis of the Surface Topography of Laser Sintered Polymer Parts }}}, doi = {{https://www.bookshop.fraunhofer.de/buch/fraunhofer-direct-digital-manufacturing-conference-ddmc-2016/245111#}}, volume = {{3}}, year = {{2016}}, } @inproceedings{22194, author = {{Josupeit, Stefan and Schmid, Hans-Joachim}}, booktitle = {{International Congress on Particle Technology (PARTEC) }}, title = {{{Thermal properties of polyamide 12 powder for application in laser sintering}}}, year = {{2016}}, } @inproceedings{22200, abstract = {{In the polymer laser sinter process, part quality depends on many influencing factors along the process chain. For application of the technology in series production and an integration of laser sintered parts into a technical environment, the dimensional accuracy of parts has to be taken into account. Therefore, occuring deviatons and their scattering have to be reduced and homogenized based on process parameters and build job layout. In this work, the dimensional accuracy of laser sintered parts is analyzed for varied parameter values. Influences of different process and geometrical build job parameters on dimensional deviatons are figured out. The experimental results allow an evaluation of more and less important influences. Finally, measures are deduced to reduce and homogenize dimensional deviations.}}, author = {{Josupeit, Stefan and Delfs, Patrick and Lieneke, Tobias and Adam, Guido and Gessler, Monika and Pfisterer, H. and Schmid, Hans-Joachim}}, booktitle = {{Rapid Tech - International Trade Show & Conference for Additive Manufacturing }}, isbn = {{978-3-446-45060-8}}, pages = {{107--120}}, title = {{{Dimensional accuracy of polymer laser sintered parts: Influences and measures}}}, doi = {{10.3139/9783446450608.009}}, year = {{2016}}, } @inproceedings{22408, author = {{Josupeit, Stefan and Delfs, Patrick and Lieneke, Tobias and Schmid, Hans-Joachim}}, booktitle = {{27th Annual International Solid Freeform Fabrication Symposium }}, title = {{{Influences on the dimensional Accuracy of Laser Sintered Parts along the Process Chain}}}, year = {{2016}}, } @article{21947, abstract = {{Wall slip is a long-known phenomenon in the field of rheology. Nevertheless, the origin and the evolution are not completely clear yet. Regarding suspensions, the effect becomes even more complicated, because different mechanisms like pure slip or slip due to particle migration have to be taken into account. Furthermore, suspensions themselves show many flow anomalies and the isolation of slip is complicated. In order to develop working physical models, further insight is necessary. In this work, we measured experimentally the wall slip velocities of different highly filled suspensions in a rectangular slit die directly with respect to the particle concentration and the particle size. The slip velocities were obtained using a particle image velocimetry (PIV) system. The suspensions consisting of a castor oil–cinnamon oil blend and PMMA particles were matched in terms of refractive indexes to appear transparent. Hereby, possible optical path lengths larger than 15 mm were achieved. The slip velocities were found to be in a quadratic relation to the wall shear stress. Furthermore, the overall flow rate as well as the particle concentration has a direct influence on the slip. Concerning the shear stress, there seem to be two regions of slip with different physical characteristics. Furthermore, we estimated the slip layer thickness directly from the velocity profiles and propose a new interpretation. The PIV technique is used to investigate the viscosity and implicit the concentration profile in the slit die. It is shown that the particle migration process is quite fast.}}, author = {{Jesinghausen, Steffen and Weiffen, Rene and Schmid, Hans-Joachim}}, issn = {{0723-4864}}, journal = {{Experiments in Fluids}}, keywords = {{Rheology, Wall Slip, Slip, apparent slip, suspension}}, title = {{{Direct measurement of wall slip and slip layer thickness of non-Brownian hard-sphere suspensions in rectangular channel flows}}}, doi = {{10.1007/s00348-016-2241-6}}, year = {{2016}}, } @phdthesis{40488, author = {{Schiller, Sascha}}, isbn = {{978-3-8440-4342-6}}, publisher = {{Shaker Verlag}}, title = {{{Zur Feinstaubabscheidung aus Holzfeuerungsanlagen mit precoatierten Oberflächenfiltern}}}, year = {{2016}}, } @article{25140, author = {{Pieper, Sven and Schmid, Hans-Joachim}}, issn = {{0377-0257}}, journal = {{Journal of Non-Newtonian Fluid Mechanics}}, pages = {{1--7}}, title = {{{Layer-formation of non-colloidal suspensions in a parallel plate rheometer under steady shear}}}, doi = {{10.1016/j.jnnfm.2016.04.004}}, year = {{2016}}, }