@inproceedings{22199, abstract = {{Powder ageing effects due to thermal load usually lead to a limited recyclability of unmolten polyamide 12 powders in the laser sintering process. In this work, the recycling optimized material PA 2221 is analyzed regarding its ageing behavior along a series of more than ten build/refresh cycles using a refresh ratio of about 30%. Thereby, the melt viscosity is measured before and after every cycle and the “steady-state” condition is determined accordingly. In addition, the material properties of parts manufactured with PA 2221 are discussed dependent on different process parameters and compared to parts made of standard PA 2200 material with a refresh rate of about 50%. These parameters include the mechanical properties as well as for example the impact strength and geometrical properties as function of layer thickness and testing temperature. As a result, the optimal process conditions and achievable material properties for PA 2221 can be derived from this work.}}, author = {{Josupeit, Stefan and Tutzschky, S. and Gessler, M. and Schmid, Hans-Joachim}}, booktitle = {{Proceedings of the Rapid Tech 2015}}, isbn = {{978-3-662-48473-9}}, pages = {{63--78}}, publisher = {{Springer Vieweg}}, title = {{{Powder ageing and material properties of laser sintered polyamide 12 using low refresh rates}}}, doi = {{10.1007/978-3-662-48473-9_5}}, year = {{2015}}, } @article{22394, abstract = {{Purpose – The purpose of this paper is to present Design Rules for additive manufacturing and a method for their development. Design/methodology/approach – First, a process-independent method for the development of Design Rules was worked out. Therefore, geometrical standard elements and attributes that characterize the elements’ shapes have been defined. Next, the standard elements have been manufactured with different attribute values with Laser Sintering, Laser Melting and Fused Deposition Modeling, and their geometrical quality was examined. From the results, Design Rules for additive manufacturing were derived and summarized in a catalogue. Findings – Due to the process independent method, Design Rules were developed that apply for the different considered additive manufacturing technologies equally. These Design Rules are completely function-independent and easily transferable to individual part designs. Research limitations/implications – The developed Design Rules can only apply for the considered boundary conditions. To extend the Design Rules’ validity, their applicability should be proven for other boundary conditions. Practical implications – The developed Design Rules practically support the design of technical parts. Additionally they can be used for training and teaching in the field of “design for additive manufacturing”. Originality/value – The developed Design Rules constitute a first step toward general Design Rules for Additive Manufacturing. Thus, they might form a suitable basis for further scientific approaches, and the Design Rules can be used to set up teaching documentations for lessons and seminars.}}, author = {{dell'Aere, Guido and Zimmer, Detmar}}, isbn = {{1355-2546}}, journal = {{Rapid Prototyping Journal}}, number = {{6}}, pages = {{662--670}}, publisher = {{Emerald Group Publishing Limited}}, title = {{{On design for Additive Manufacturing - evaluating geometrical limitations}}}, doi = {{10.1108/RPJ-06-2013-0060}}, volume = {{21}}, year = {{2015}}, } @inproceedings{22395, author = {{Lieneke, Tobias and Adam, Guido and Leuders, Stefan and Knoop, Frederick and Josupeit, Stefan and Delfs, Patrick and Funke, Nils and Zimmer, Detmar}}, booktitle = {{Proceedings of the Rapid Tech 2015}}, title = {{{Entwicklung einer Methode zur systematischen Erarbeitung von Maßtoleranzen für additive Fertigungsverfahren}}}, year = {{2015}}, } @inproceedings{22396, abstract = {{Additive manufacturing offers many technical and economical benefits. In order to profit from these benefits, it is necessary to consider the manufacturing limits and restrictions. This applies in particular to the geometrical accuracy. Therefore, the achievable geometrical accuracy needs to be investigated, which enables the determination of realistic tolerances. Thus, two different aims are considered. The first aim is the determination of dimensional tolerances that can be stated if additive manufacturing is used under normal workshop conditions. Within the second aim, relevant process parameters and manufacturing influences will be optimized in order to reduce dimensional deviations. To achieve both aims a method was developed first. This method identifies relevant influential factors on the geometrical accuracy for the processes Fused Deposition Modeling (FDM), Laser Sintering (LS) and Laser Melting (LM). Factors were selected that are expected to affect the geometrical accuracy mainly. The first investigations deal with measuring linear dimensions on a designed test specimen and the derivation of achievable dimensional tolerances. This paper will present both, the developed method and the first results of the experimental investigations.}}, author = {{Lieneke, Tobias and Adam, Guido and Leuders, Stefan and Knoop, Frederick and Josupeit, Stefan and Delfs, Patrick and Funke, Nils and Zimmer, Detmar}}, booktitle = {{26th Annual International Solid Freeform Fabrication Symposium}}, pages = {{371--384}}, title = {{{Systematical determination of tolerances for additive manufacturing by measuring linear dimensions}}}, doi = {{https://www.researchgate.net/publication/316827402_Systematical_Determination_of_Tolerances_for_Additive_Manufacturing_by_Measuring_Linear_Dimensions}}, volume = {{26}}, year = {{2015}}, } @phdthesis{22397, author = {{Adam, Guido}}, isbn = {{978-3-8440-3474-5}}, publisher = {{Shaker Verlag}}, title = {{{Systematische Erarbeitung von Konstruktionsregeln für die additiven Fertigungsverfahren Lasersintern, Laserschmelzen und Fused Deposition Modeling}}}, year = {{2015}}, } @inproceedings{22398, author = {{Adam, Guido}}, booktitle = {{Inside 3D Printing Conference and Expo}}, title = {{{On tolerances for additive manufacturing}}}, year = {{2015}}, } @inproceedings{22399, author = {{Lieneke, Tobias}}, booktitle = {{Rapid Tech 2015}}, title = {{{Entwicklung einer Methode zur systematischen Erarbeitung von Maßtoleranzen für additive Fertigungsverfahren}}}, year = {{2015}}, } @inproceedings{22400, author = {{Lieneke, Tobias}}, booktitle = {{26th Annual International Solid Freeform Fabrication Symposium}}, title = {{{Systematical determination of dimensional tolerances for additive manufacturing }}}, volume = {{26}}, year = {{2015}}, } @inproceedings{21683, abstract = {{Purpose – This paper aims to present a methodology to help end-users to find appropriate part candidates for the use of the additive manufacturing (AM) technology. These shall be capable of bringing AM into their businesses. The concept furthermore includes approaches for redesigning current available parts and helps to estimate the economic implications of the use of the technology. Design/methodology/approach – The approach starts to discuss general economic aspects for the successful use of AM. While describing the introduction of new technologies into existing businesses, the importance of an appropriate part selection for AM is pointed out. A methodology for a part selection process is presented, and the different criteria are developed. An approach for a redesign of the selected parts, including the gathering of requirements, is given based on different sample parts. A variation of criteria to include measures for product piracy is highlighted. Findings – The methodology has proven applicability in several research and industry projects in aerospace applications. Independent part selections from experts analyzed within a project of the European Space Agency had a 90 per cent overlap with the results. It allows companies with only basic AM knowledge to start a part screening for applicable AM candidates in their own company with a reasonable effort. Originality/value – The methodology for the redesign process helps to identify the main functions of the products targeted and the relevant environment, so one can benefit from the various advantages that AM has to offer. The selection methodology helps to ask the right questions and to reduce the effort.}}, author = {{Lindemann, C. and Jahnke, U. and Reiher, T. and Koch, R.}}, booktitle = {{Rapid Prototyping Journal}}, isbn = {{1355-2546}}, number = {{2}}, pages = {{216--227}}, publisher = {{Emerald}}, title = {{{Towards a sustainable and economic selection of part candidates for Additive Manufacturing}}}, doi = {{https://doi.org/10.1108/RPJ-12-2014-0179}}, volume = {{21}}, year = {{2015}}, } @inproceedings{21684, abstract = {{Additive Manufacturing offers a high potential in aerospace industry due to its freedom of design and the ability to manufacture complex and lightweight parts. The low number of units, high quality standards and fast response time are special challenges that have to be met especially in the Maintenance, Repair and Overhaul sector. Thus, companies have to decide at which point it is economic to apply Additive Manufacturing. However, companies lack experience on this new technology. This is why a tool is required that takes into account the above mentioned crucial points and supports the decision process. The paper analyzes aviation’s characteristics with regard to Additive Manufacturing. The structure of current MRO repair workflows is investigated to identify a feasible application for Additive Manufacturing. Additionally the supply chain will be examined to indicate the benefit which the technology can generate in this highly demanding field. The findings are integrated into a methodology that supports the decision whether to apply Additive Manufacturing on the basis of costs, time and quality.}}, author = {{Deppe, G. and Lindemann, C. and Koch, R.}}, booktitle = {{26th Annual International Solid Freeform Fabrication Symposium}}, pages = {{1560--1563}}, title = {{{Developement of an economic decision support for the application of Additive Manufacturing in aerospace}}}, doi = {{http://utw10945.utweb.utexas.edu/sites/default/files/2015/2015-125-Deppe.pdf}}, volume = {{26}}, year = {{2015}}, } @inproceedings{21685, abstract = {{Presently the implications Additive Manufacturing (AM) on intellectual properties are discussed in public. Here AM is often mentioned as a driver for product piracy as it allows to produce and to copy objects with any geometries. Imitators need a lot of information to copy an object accurately. As reverse engineering has been identified as the most important information source for product imitators, AM can also help to reduce the threat of product piracy when correctly applied in the product development. Due to the layer wise production process that allows the manufacturing of very complex shapes and geometries, the reverse-engineering process can be complicated by far. By this, quite contrary to the public opinion, AM can increase the needed effort of imitators and strongly reduce the economic efficiency of product piracy. This paper will show different protection measures and a methodological approach of how to apply these measures to a product. Beside the protective effect some measures allow a traceability of parts over the product’s lifecycle and thus support the quality management of AM processes and additively produced parts. }}, author = {{Jahnke, U. and Büsching, J. and Reiher, T. and Koch, R.}}, booktitle = {{26th Annual International Solid Freeform Fabrication Symposium}}, pages = {{1601--1611}}, title = {{{Protection measures against product piracy and application by the use of AM}}}, doi = {{http://utw10945.utweb.utexas.edu/sites/default/files/2015/2015-128-Jahnke.pdf}}, volume = {{26}}, year = {{2015}}, } @inproceedings{21686, abstract = {{Additive Manufacturing (AM) offers high potential due to its freedom of design for structural parts. Especially in combination with FE-based topology optimization an optimal use of material and thus significant weight reductions can be expected. However, the application of AM is hampered by different additional manufacturing processes along the entire production chain and data handling induced restrictions.Disadvantages emerge from a lack of adjustment of the entire design process for AM. First the optimization algorithms are not targeted to the opportunities and restrictions of AM –represented by design rules – like the design of support structures. Secondly, the CAD software is not adjusted to AM in particular. Creating freeform shaped surfaces based on the optimization results is significantly less convenient than building defined blocks or turning parts following the needs of conventional machining. The indispensable subsequent interpretation of optimization results regarding the design rules and the possibilities of CAD-tools counteracts optimal results. This paper considers different approaches for a Topology Optimization (TO)-shape regaining on different sample parts including telecommunication satellite parts. An innovative design methodology is presented getting crucial for creating high quality designs. }}, author = {{Reiher, T. and Koch, R.}}, booktitle = {{26th Annual International Solid Freeform Fabrication Symposium}}, pages = {{1092--1103}}, title = {{{FE-Optimization and data handling for Additive Manufacturing of structural parts}}}, doi = {{http://utw10945.utweb.utexas.edu/sites/default/files/2015/2015-90-Reiher.pdf}}, volume = {{26}}, year = {{2015}}, } @inproceedings{21700, author = {{Jahnke, U. and Lindemann, C.}}, booktitle = {{Inside 3D Printing Conference and Expo}}, title = {{{Sustainable Part Selection for the Use of Additive Manufacturing in Companies Focussing on Prevention of Product Piracy}}}, year = {{2015}}, } @inproceedings{21701, abstract = {{The aerospace sector is characterized by long product life cycles and a need for lightweight design. Additive manufacturing is a technology that produces parts layer by layer and thus enables the manufacturing of any complex parts at nearly no extra costs. A topology optimization enhances the part’s performance for their special purpose. The results are often complex bionic structures that cannot be produced with conventional manufacturing technologies. The paper analyzes how the high potential of this technology can be applied to aerospace parts. A topology optimization will be conducted for an aircraft part explaining the crucial points and a life cycle analysis examines the achieved sustainable improvements for the aircraft’s life cycle.}}, author = {{Deppe, G. and Reiher, T. and Koch, R.}}, booktitle = {{International Conference Production Engineering and Management 2015}}, isbn = {{9783941645110}}, pages = {{219--230}}, title = {{{Exploring the cost and lifetime benefits of a topology optimized aerospace part applying additive manufacturing}}}, doi = {{https://www.th-owl.de/elsa/download/335/336/PEM_Tagung_zusammen2015.pdf}}, volume = {{5}}, year = {{2015}}, } @inproceedings{21703, author = {{Lindemann, C. and Reiher, T. and Koch, R.}}, booktitle = {{Paris Space Week}}, title = {{{Guidelines for a sustainable and economic selection of part candidates for space applications using additive manufacturing}}}, year = {{2015}}, } @inproceedings{22031, author = {{Knoop, F. and Schöppner, Volker}}, booktitle = {{ASPE Spring Topical Meeting}}, pages = {{26--31}}, title = {{{Analysis and Optimization of the Dimensional Accuracy for FDM Parts manufactured with ABS-M30}}}, doi = {{https://www.researchgate.net/publication/283735736_Analysis_and_optimization_of_the_dimensional_accuracy_for_FDM_parts_manufactured_with_ABS-M30}}, year = {{2015}}, } @inproceedings{22044, abstract = {{Fused Deposition Modeling (FDM) is an Additive Manufacturing (AM) technology which is used for prototypes, single-part production and also small batch productions. For use as a final product, it is important that the parts have good mechanical properties, high dimensional accuracy and smooth surfaces. The knowledge of the mechanical properties is very important for the design engineer when it comes to the component design. End-use products out of the FDM process have to resist applied forces. In this paper, investigations were conducted with the polymer Polyamide 12 (FDM Nylon 12) from Stratasys Inc. This polymer can be processed with three different tip sizes resulting in different layer thicknesses from 178 µm to 330 µm. Thus, the mechanical properties were determined for these layer thicknesses and for different orientations on the build platform. In addition to the mechanical properties the thermal properties (e.g. with a DSC analysis) are also investigated.}}, author = {{Knoop, F. and Schöppner, Volker}}, booktitle = {{26th Annual International Solid Freeform Fabrication Symposium}}, pages = {{935--948}}, title = {{{Mechanical and Thermal Properties of FDM Parts manufactured with Polyamide 12}}}, doi = {{http://utw10945.utweb.utexas.edu/sites/default/files/2015/2015-77-Knoop.pdf}}, volume = {{26}}, year = {{2015}}, } @inproceedings{22176, abstract = {{One barrier of laser sintering (LS) to become the main process for Direct Manufacturing (DM) is the surface quality of LS parts. Hence, the property which has to be improved is the rough surfaces of LS parts due to the layered structure. Another additional effect is the incomplete melting of powder particles on the surface due to the high process temperature. In this paper we demonstrate our approach of a theoretical model for the topography of LS part surfaces. We investigated the surface roughness as a function of surface orientation. Considering that the model involves further variables as layer thickness, particle density and particle size distribution to describe the topography precisely. Experimental results were used to optimize and check the results of the model.}}, author = {{Delfs, Patrick and Herale, A.A. and Li, Z. and Schmid, Hans-Joachim}}, booktitle = {{25th Annual International Solid Freeform Fabrication Symposium}}, pages = {{1250--1258}}, title = {{{Simulation of the Surface Topography on Laser Sintered Polymer Parts}}}, doi = {{http://utw10945.utweb.utexas.edu/sites/default/files/2014-098-Delfs.pdf}}, volume = {{25}}, year = {{2014}}, } @inproceedings{22177, abstract = {{An uneven temperature distribution and varying cooling rates at different positions within the part cake are two of the most important challenges regarding the part quality and reproducibility of the polymer laser sintering process. In the presented work, a temperature measurement system is implemented within an EOSINT P395 laser sintering system. It allows the determination of a three dimensional temperature distribution and history during the full build and cooling process. The influence of important job parameters, for example the packing density, job height and layer thickness, can be figured out. In combination with a finite element simulation of the cooling process, the temperature measurement will be the basis for optimized process controls.}}, author = {{Josupeit, Stefan and Schmid, Hans-Joachim}}, booktitle = {{25th Annual International Solid Freeform Fabrication Symposium}}, pages = {{49--58}}, title = {{{Three-dimensional in-process temperature measurement of laser sintered part cakes}}}, doi = {{http://utw10945.utweb.utexas.edu/sites/default/files/2014-006-Josupeit.pdf}}, volume = {{25}}, year = {{2014}}, } @inproceedings{22184, abstract = {{Polymer laser sintering is one of the most important additive manufacturing technologies for the tool-less production of three-dimensional prototypes and end-use parts. In this process, parts are manufactured layerwise out of a polymer powder by laser exposure. After the building process, these parts are located within a loose bulk powder cake. Due to long process times and high process temperatures, this powder ages thermally, which reduces the recyclability of the material. As a result, mixtures of used and virgin powder ("refreshed" powder) with a mixture ratio of approximately 50% are commonly used in the industry. The goal of this work is to determine the exact influence of different powder ages on resulting part quality characteristics, especially the mechanical behavior and the surface quality. Therefore, refreshed powder with different qualities adjusted by the melt volume rate (MVR) was processed along a defined process quality chain. To analyze the part qualities, mechanical tensile and profilometer tests were performed. The focus is on an application-oriented test set-up to ensure the usability of the results in the industry. The material used is polyamide 12 (PA 2200) processed on an EOSINT P395 laser sintering system from EOS GmbH, Krailling, Germany.}}, author = {{Josupeit, Stefan and Rüsenberg, Stefan and Rupp, N. and Gessler, Monika and Schmid, Hans-Joachim}}, booktitle = {{72nd Annual Technical Conference of the Society of Plastics Engineers (ANTEC 2014)}}, isbn = {{978-1-634-39708-7}}, number = {{3}}, pages = {{2383--2385}}, title = {{{Thermal ageing of polyamide 12 used for polymer laser sintering - influence on part quality characteristics}}}, doi = {{https://www.researchgate.net/publication/283135483_Thermal_ageing_of_polyamide_12_used_for_polymer_laser_sintering_-_Influence_on_part_quality_characteristics}}, volume = {{72}}, year = {{2014}}, }