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iCAT 2016: Proceedings of the 6th International Conference on Additive Technologies, ISBN:978-961-285-537-6

Journal of Sensors, 2016, ISSN:1687-725X, ISSN:1687-7268

Essentials, ISBN:3-658-12288-9, ISBN:978-3-658-12288-1

Selective Laser Sintering (SLS) is close to be accepted as a production technique (Additive Manufacturing). However, one problem limiting employment of SLS for additive manufacturing in a wide-ranging industrial scope is the narrow variety of applicable polymers. The commonly applied SLS powder to date is polyamide 12 (PA 12). PA 12 or ccompounds of PA 12 (dry blends) are approximately 90 % of complete industrial consumption. The remaining small quantity is distributed on polyamide 11 (PA11) and some other ‘exotic’ polymers (TPU, PEBA, P(E)EK). Industry is awaiting commodity polymers like polypropylene (PP) or polyethylene (PE) crucial to open new market segments. But several approaches launching those polymers failed. But what are the reasons for the difficulties in developing new SLS powders? The contribution is to answer this and highlights the combination of intrinsic and extrinsic polymer properties necessary to generate a polymer powder promising for SLS application. Particle shape, powder distribution, thermal, rheological and optical requirements must be considered and only a particularly controlled property combination leads to successful SLS implementation. Thermal behavior, particle shape and –distribution is discussed in detail, although the other properties can’t be disregarded for providing new commercially successful SLS powder finally.

High Value Manufacturing : Proceedings of the 6th International Conference on Advanced Research in Virtual and Rapid Prototyping, Leiria, Portugal, 1-5 October, 2013, ISBN:978-1-315-81741-5, ISBN:978-1-138-00137-4

Polymer processing using Additive Manufacturing Technologies (AM) has experienced a remarkable growth during the last years. The application range has been expanding rapidly, particularly driven by the so-called consumer 3D printing sector. However, for applications demanding higher requirements in terms of thermo-mechanical properties and dimensional accuracy the long established AM technologies such as Selective Laser Sintering (SLS) do not depict a comparable development. The higher process complexity hinders the number of materials that can be currently processed and the interactions between the different physics involved have not been fully investigated. In case of thermoplastic materials the crystallization kinetics coupled to the shrinkage strain development strongly influences the stability of the process. Thus, the current investigation presents a transient Finite Element simulation of the warpage effect during the SLS process of a new developed polyolefin (co-polypropylene) coupling the thermal, mechanical and phase change equations that control the process. A thermal characterization of the material was performed by means of DSC, integrating the Nakamura model with the classical Hoffmann-Lauritzen theory. The viscoelastic behavior was measured using a plate-plate rheometer at different degrees of undercooling and a phase change-temperature superposition principle was implemented. Additionally, for validation porpoises the warpage development of the first sintered layers was captured employing an optical device. The simulation results depict a good agreement with experimental measurements of deformation, describing the high sensitivity of the geometrical accuracy of the sintered parts related to the processing conditions.

Rapid Prototyping Journal, 21 (2), ISSN:1355-2546

DDMC 2014 : Fraunhofer Direct Digital Manufacturing Conference : proceedings, ISBN:978-3-8396-9128-1

Additive Manufacturing technologies are known to allow the production of parts with an extreme degree of complexity, enabling design and functional part optimization. So far the development of processing parameters and analyze of corresponding materials focuses on dense materials for maximized material properties. However, AM processes like Selective Laser Melting, allow also the generation of materials with some degree of porosity affecting their mechanical properties. A DOE was set up for SLM processed SS 17-4PH / AISI-630 material with porosity between 0% and about 26% in order to analyze mechanical properties. The results presented show that the porosity significantly affects material ductility and hardness, offering the possibility to design a material according to the required mechanical behavior of the parts produced. Therefore, this AM enabling features allows a multi-property component design by appropriate local parameter setting.

RTejournal, 7, ISSN:1614-0923