Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Numerical investigation into cleanability of support structures produced by powder bed fusion technology
    ( 2022)
    Campana, Giampaolo
    ;
    Uhlmann, Eckart
    ;
    Mele, Mattia
    ;
    Raffaelli, Luca
    ;
    Bergmann, André
    ;
    Kochan, Jaroslaw
    ;
    Polte, Julian
    Purpose: Support structures used in laser powder bed fusion are often difficult to clean from unsintered powder at the end of the process. This issue can be significantly reduced through a proper design of these auxiliary structures. This paper aims to investigate preliminary the airflow within differently oriented support structures and to provide design guidelines to enhance their cleanability, especially the depowdering of them. Design/methodology/approach: This study investigates the cleanability of support structures in powder bed fusion technology. Digital models of cleaning operations were designed through computer-aided engineering systems. Simulations of the airflow running into the powder entrapped within the thin walls of auxiliary supports were implemented by computational fluid dynamics. This approach was applied to a set of randomly generated geometrical configurations to determine the air turbulence intensity depending on their design. Findings: The resul ts, which are based on the assumption that a relationship exists between turbulence and powder removal effectiveness, demonstrated that the maximum cleanability is obtainable through specific relative rotations between consecutive support structures. Furthermore, it was possible to highlight the considerable influence of the auxiliary structures next to the fluid inlet. These relevant findings establish optimal design rules for the cleanability of parts manufactured by powder bed fusion processes. Originality/value: This study presents a preliminary investigation into the cleanability of support structures in laser powder bed fusion, which has not been addressed by previous literature. The results allow for a better understanding of the fluid dynamics during cleaning operations. New guidelines to enhance the cleanability of support structures are provided based on the results of simulations.
  • Publication
    Application of additive manufactured tungsten carbide-cobalt electrodes with interior flushing channels in S-EDM
    ( 2020)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Bolz, Robert
    ;
    Yabroudi, Sami
    ;
    Streckenbach, Jan
    ;
    Bergmann, André
    Application fields of electrical discharge machining (EDM) are limited due to given process conditions. Manufacturing of parts with high aspect ratios and the application of multi-axis machining are limited due to process instabilities caused by removed particles. A promising approach to improve EDM process conditions, especially in sinking EDM (S-EDM), is the utilization of flushing channels in the tool electrode. However, with increasing complexity of the tool electrode geometry and the local integration of these flushing channels, conventional tool electrode manufacturing by cutting is limited. In contrast to that, the machining process selective laser melting (SLM) does not have such limitations. The appropriate integration of flushing channels, even for complex electrode geometries, improves process conditions during EDM in a variety of applications. This leads to a higher material removal rate and reduced tool wear compared to machining without flushing. Additionally, the number of required tool electrodes can be reduced, as SLM enables an efficient integration and miniaturization of all features in a single electrode. Because of its wear resistance and stability, tungsten carbide is an ideal tool electrode material, which is commonly applied in drilling EDM. After identifying suitable process parameters for roughing EDM with additively manufactured tungsten carbide cobalt tool electrodes, different forms of flushing channels were analysed in order to establish a fast process with minimum tool electrode wear. The results concerning material removal rate and the relative tool wear could be improved by applying internal flushing, though the tool wear stayed at a worse level compared to conventional tool electrode materials.
  • Publication
    Concept of sustainable data for a selective laser melting machine
    ( 2018)
    Uhlmann, Eckart
    ;
    Pastl Pontes, Rodrigo
    ;
    Laghmouchi, Abdelhakim
    ;
    Bergmann, André
    Due to increased digitalization in the production environment, data, information, and sustainable management approaches should be developed in order to enable production machines for data acquisition, data exchange and data analysis. Especially for additive manufacturing technologies, those approaches are extremely important to detect and avoid failures in the manufacturing process. A critical failure during the manufacturing process could lead to a defective workpiece, wasting resources. Within this context, this work addresses the concept of sustainable data for a selective laser melting machine tool. The selective laser melting process is one of the additive manufacturing technologies that is capable of producing lighter and more complex functional workpieces in comparison to conventional manufacturing technologies. Beyond the use of the machine tool system internal data (e.g. process data, internal sensors), additional information such as energy consumption and data provided using external sensors are required to detect the current condition of production process. In order to observe if the considered data sources are capable of identifying abnormal conditions of the machine tool, failures from five subsystems were inserted during a manufacturing process of a reference workpiece. Four of the five data sources detect failures that influenced the layer quality while they are occurring. Thus, the results could be used to allow the operator to take measures to save energy and resources.
  • Publication
    Application of additive manufactured tungsten carbide tool electrodes in EDM
    ( 2018)
    Uhlmann, Eckart
    ;
    Bergmann, André
    ;
    Bolz, Robert
    ;
    Gridin, Witalij
    Application fields of electrical discharge machining (EDM) are limited due to given process conditions. When producing structures of high aspect ratios or using multi-axis machining, removed particles assemble at the machining zone, leading to process instabilities. A promising approach to improve EDM process conditions is the utilization of flushing channels in the tool electrode. However, with increasing complexity of the electrode geometry and the local integration of the mentioned flushing channels, conventional electrode manufacturing reaches its limitations. By applying Selective Laser Melting (SLM), these limitations are eliminated. The appropriate integration of flushing channels, even for complicated electrode geometries, improves process conditions during EDM in a variety of applications, leading to a higher material removal rate VW and reduced tool wear TH compared to machining without flushing. Additionally, the number of required tool electrodes can be reduced, as SLM enables an efficient integration and miniaturization of all features in a single electrode. Of particular interest in the field of EDM is carbide. Because of its wear resistance and stability, it is an ideal electrode material, which is commonly applied in mEDM. Tungsten carbide-cobalt is representative for this group of materials, which is already used in tool manufacturing. Several tests show a general suitability of carbide tool electrodes made by SLM for EDM-processing. However, the SLM process parameters and the composition of the carbide-cobalt show significant impact to the EDM results. A lower proportion of cobalt leads to reduced material removal rates VW and rising tool wear.
  • Publication
    Manufacturing of carbide tools by Selective Laser Melting
    ( 2018)
    Uhlmann, Eckart
    ;
    Bergmann, André
    ;
    Bolz, Robert
    Application fields of electrical discharge machining (EDM) are limited due to given process conditions. When producing structures of high aspect ratios or using multi-axis machining, removed particles assemble at the machining zone, leading to process instabilities and increasing tool wear. A promising approach to improve EDM process conditions is the utilization of flushing channels in the tool electrode. However, with increasing complexity of the electrode geometry and the local integration of the mentioned flushing channels, conventional electrode manufacturing reaches its limitations. By applying Selective Laser Melting (SLM), these limitations are eliminated. An additional benefit is the efficient use of material during SLM, where nearly no waste is produced, because remaining powder can be used for the next SLM-process. The appropriate integration of flushing channels, even for complicated electrode geometries, improves process conditions during EDM in a variety of applications, leading to a higher material removal rate VW and reduced tool wear TH compared to machining without flushing. Additionally, the number of required tool electrodes can be reduced, as SLM enables an efficient integration and miniaturization of all features in a single electrode, what results in a far more sustainable process chain. Of particular interest in the field of EDM is carbide. Because of its wear resistance and stability, it is an ideal electrode material, which is commonly applied in µEDM. Tungsten carbide-cobalt is representative for this group of materials, which is already used in tool manufacturing. Several tests show a general suitability of carbide tool electrodes made by SLM for EDM-processing. However, the SLM process parameters and the composition of the carbide-cobalt show significant impact to the EDM results. A lower proportion of cobalt leads to reduced material removal rates, whereas the level of tool wear remains at a similar level. In order to benefit from the advantages of additive manufactured carbide tool electrodes, this investigation aims at decreasing waste of material and the number of required tool electrodes.
  • Publication
    Contribution to a database of Ti-6Al-4V components manufactured with selective laser melting process
    ( 2017)
    Uhlmann, Eckart
    ;
    Bergmann, André
    ;
    Gridin, Witalij
    ;
    Rolon, Daniel Alexandre
    In summary, the components manufactured additively through SLM proved to have characteristics similar to conventionally manufactured parts in high temperatures. Especially when testing the material properties with temperatures higher than 300 °C. This assumption is not only supported by a quantitative analysis of the material properties, but also by characterizing the microstructure of the SLM samples. Moreover, a database is constituted, which can help to design and plan components built using SLM through extensive simulations. Future works, should study the different possibilities of constructing the tensile test samples. Moreover, studies could focus on other types of super alloys such as Inconel 718, which is often employed in the same context as Ti-6Al-4V.
  • Publication
    High level process map for Selective Laser Melting
    ( 2016)
    Uhlmann, Eckart
    ;
    Pastl Pontes, Rodrigo
    ;
    Bergmann, André