Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Framework of an experimental setup to enable an adaptive process control based on surrogate modelling
    ( 2022)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Bösing, Manuel
    ;
    Schuler, Niklas
    Numerical simulations can help to reduce the necessity of experimental studies. Nevertheless, these simulations are costly in terms of their computational effort resulting in significant expenditure of time and hence prevent a flexible adaption to continuously changing process conditions in real time. To address this shortcoming, the paper describes a framework for the application of surrogate models to enable an adaptive process control in real time. Following, an experimental setup to validate the general framework is designed for a laser metal deposition process. In particular, the component distortion shall be simulated and the results are then used to train the surrogate models. By measuring the final component distortion the quality of the surrogate models can be assessed.
  • Publication
    Residual stresses in additive manufactured precision cemented carbide parts
    ( 2022)
    Polte, Julian
    ;
    Polte, Mitchel
    ;
    Hocke, T.
    ;
    Blankenburg, Malte
    ;
    Lahoda, Christian
    ;
    Uhlmann, Eckart
    Due to the good strength properties and high hardness, components made of cemented carbide are used in various industrial sectors as key components, e.g. mould making and matrices. Precision cemented carbide parts are mainly machined by milling and electrical discharge machining (EDM). Nevertheless, long machining times and excessive tool wear are remaining challenges at the state of the art. A promising approach to overcome these challenges is the machining of precise cemented carbide parts using a process chain consisting of near-net-shape laser powder bed fusion (LPBF) and subsequent finishing using a dedicate diamond slide burnishing process. Within previous investigations a geometrical accuracy of ag ≤ 10 µm and a reduction of the surface roughness by Ra = 89 % could be achieved. Within this work plastic deformation induced by the diamond slide burnishing and the effects on the material properties in the surface area were investigated, e.g. residual stresses. For this purpose, the lattice distortion of the metallic cobalt phase was measured by X-ray diffraction using high-energy synchrotron radiation. In addition, the height profile of the residual stresses was also recorded in distances of d = 3 µm to obtain information about the depth effect of the diamond slide burnishing process. Based on the investigations an increase of the residual compressive stresses could be obtained. This shows a particularly positive effect especially for additively manufactured components, as these often show a slight porosity and higher surface roughness as conventional manufactured components. In this way, crack propagation can be prevented and the fatigue strength can be increased.
  • Publication
    Additive manufacturing of precision cemented carbide parts
    ( 2021)
    Polte, Julian
    ;
    Polte, Mitchel
    ;
    Lahoda, Christian
    ;
    Hocke, Toni
    ;
    Uhlmann, Eckart
    Cemented carbide parts are commonly used as wear resistance components in a broad range of industry, e.g. for forming, mould making and matrices. At state of the art the machining of precision cemented carbide components by milling is strongly limited due to excessive tool wear and long machining times. Promising approaches for precision machining of cemented carbide components are dedicated cutting tool coatings, new cutting materials like binderless polycrystalline diamond and ultrasonic-assisted machining. Nevertheless, for all these approaches the components need to be machined of monolithic materials. The new approach addresses an innovative manufacturing process chain composed of near net shape Additive Manufacturing followed by a precision finishing process. Within this investigations for the manufacturing of precision cemented carbide parts, cemented carbide with a cobalt content of 17 % and a grain size in a range of 23 µm ⤠gs ⤠40 µm were used. As Addit ive Manufacturing technology laser powder bed fusion was used. Diamond slide burnishing and immersed tumbling were investigated as finishing technologies. Based on the investigations, a dedicated process chain for the manufacturing of precision cemented carbide parts could be realised. The findings show that the developed process chain composed of near net shape Additive Manufacturing and the finishing process diamond slide burnishing enables the manufacturing of precision cemented carbide parts with a geometrical accuracy of ag ⤠10 µm. Due to the finishing process the initial surface roughness after Additive Manufacturing could reduce by Ra = 89 %.
  • Publication
    Effects on part density for a highly productive manufacturing of WC-Co via laser powder bed fusion
    ( 2021)
    Polte, Julian
    ;
    Neuwald, Tobias
    ;
    Gordei, Anzhelika
    ;
    Kersting, Robert
    ;
    Uhlmann, Eckart
    The additive manufacturing of parts made from difficult-to-weld materials through the usage of preheating temperatures of up to Î0 ⤠500 °C is enabled by newest L-PBF machine tools, such as the RenAM 500Q HT from the company RENISHAW PLC, Wottun-under-Edge, UK. This work aims to delevop processing parameters for the dense and crack-free manufacturing of tungsten-carbide cobalt (WC-Co) via this off-the-shelf machine tool. Therefore the laserpower and scanning speed were varied between 80 W ⤠PL ⤠350 W and 140 mm/s ⤠vS ⤠650 mm/s respectively. Furthermore the influence of a continuous and pulsed laser mode was analysed. A focus was set on the identification of parameters that enable a highly productive manufacturing while maintaining a high part density. A parameter set for relative density rel. > 94 % and a buildup rate v = 0.59 mm3/s was developed.
  • Publication
    Heat treatment of SLM-LMD hybrid components
    ( 2019)
    Uhlmann, Eckart
    ;
    Düchting, Jan
    ;
    Petrat, Torsten
    ;
    Graf, Benjamin
    ;
    Rethmeier, Michael
    Additive manufacturing is no longer just used for the production of prototypes but already found its way into the industrial production. However, the fabrication of massive metallic parts with high geometrical complexity is still too time-consuming to be economically viable. The combination of the powder bed-based selective laser melting process (SLM), known for its geometrical freedom and accuracy, and the nozzle-based laser metal deposition process (LMD), known for its high build-up rates, has great potential to reduce the process duration. For the industrial application of the SLM-LMD hybrid process chain it is necessary to investigate the interaction of the processes and its effect on the material properties to guarantee part quality and prevent component failure. Therefore, hybrid components are manufactured and examined before and after the heat treatment regarding the microstructure and the hardness in the SLM-LMD transition zone. The experiments are conducted using the nickel-based alloy Inconel 718.
  • Publication
    Use of Digital Twins in Additive Manufacturing Development and Production
    ( 2019)
    Bergmann, André
    ;
    Lindow, Kai
    The megatrend of the digitization of the industry is picking up speed. Today, the digital twin is an important component in the strategic positioning of a manufacturing company. The Gartner Report predicts that more than 50% of large industrial companies will be using the digital twin and that the effectiveness of the companies can be increased by up to 10% by 2021. For this, it is necessary on the one hand that the products are equipped with sensors, in order to be able to provide the data for the digital twin. On the other hand, it is also necessary to be capable to evaluate the data unambiguously with regard to the products and to be able to initiate appropriate measures to control them. In addition, insights can be gained into the improvement of subsequent product generations and their production. The virtual representation of the product over its lifecycle requires a coupling with the real environment, in which lifecycle data are recorded via sensory systems and continuously imported into the virtual environment. Thus, the information and actual properties in the digital twin are mapped to the real conditions and the product condition in a dynamic data model. For this, it is necessary to integrate the information into the data systems of the product development and manufacturing processes. Based on this data, the behavior can be virtually tested, analyzed and predicted before actual production and use. This enables the engineer and manufacturer to further develop the product at reduced costs as early as the design phase. The virtual validation is significantly extended by the collected database in the digital twin. For companies, this means a reduction of costs by reducing material and time expenditures as well as process times - for example, with increased utilization time. On the basis of this study, a product example will be used to show which framework conditions are necessary for the use of the digital twin and which effects can be achieved in product development. It is also estimated to what extent the quality of the product and the process can be improved. In the area of additive manufacturing, for example, the question arises how quality data can be used either to control the machine parameters of the printing process in a targeted manner (feedback-to-planning) so that the desired product quality is achieved, or to adapt the product models before manufacturing (feedback-to-engineering) so that the desired product quality can be produced with existing parameters. The data alone is of little use to the companies. In addition to methodological and organizational issues, it is also necessary at the technological level to prepare the data for the various lifecycle phases of the product development process. This is where automated data evaluation in the form of AI comes in. Algorithms allow data evaluation by identifying patterns and deviations and consequently interpreting them for feedback-to-planning and feedback-to-engineering.
  • Publication
    3D laser metal deposition in an additive manufacturing process chain
    ( 2017)
    Graf, Benjamin
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Laser metal deposition (LMD) is an established technology for two-dimensional surface coatings. It offers high deposition rates, high material flexibility and the possibility to deposit material on existing components. Due to these features, LMD has been increasingly applied for additive manufacturing of 3D structures in recent years. Compared to previous coating applications, additive manufacturing of 3D structures leads to new challenges regarding LMD process knowledge. In this paper, the process chain for LMD as additive manufacturing technology is described. The experiments are conducted using titanium alloy Ti-6Al-4V and Inconel 718. Only the LMD nozzle is used to create a shielding gas atmosphere. This ensures high geometric flexibility, although issues with the restricted size and quality of the shielding gas atmosphere arise. In the first step, the influence of process parameters on the geometric dimensions of single weld beads is analysed based on design of experiments and statistical evaluation. The results allow adjusting the weld bead dimensions for the specific component geometry. In the second step, features of a 3D build-up strategy for high dimensional accuracy are discussed. For this purpose, cylindrical specimens consisting of more than 200 layers are built. Welding of multiple layers on top of each other leads to heat accumulation. Consequently, the molten pool is increased and weld bead height and width are changed. Furthermore, cooling times are prolonged. The build-up strategy has to be adjusted to deal with these issues. Process parameters, travel paths and cooling breaks between layers are varied. Temperatures during the deposition process are measured with pyrometer and thermography. The specimens are analysed with metallurgic cross sections, x-ray and tensile test. Tensile tests show that mechanical properties in the as-deposited condition are close to wrought material. The results are used to design guidelines for a LMD build-up strategy for complex components. As reality test, parts of a gas turbine burner and a turbine blade are manufactured according to these build-up strategies. Build-up rate, net-shape and microstructure of these demonstrative components are evaluated. This paper is relevant for industrial or scientific users of LMD, who are interested in the feasibility of this technology for additive manufacturing.
  • Publication
    Laser-Pulver-Auftragschweißen zum additiven Aufbau komplexer Formen
    ( 2015)
    Petrat, Torsten
    ;
    Graf, Benjamin
    ;
    Gumenyuk, Andrey
    ;
    Rethmeier, Michael
    Das Laser-Pulver-Auftragschweißen als additives Fertigungsverfahren ermöglicht einen endformnahen Aufbau von Bauteilen. Ein Zielkonflikt besteht zwischen der Forderung nach hoher Aufbaurate und hoher Endformnähe, welcher von der Schweißraupengröße wesentlich beeinflusst wird. In dieser Veröffentlichung wird das Laser-Pulver-Auftragschweißen eingesetzt, um komplexe Formen additiv aufzubauen. Am Beispiel eines Tannenbaumprofiles werden unterschiedliche Einflussfaktoren dargestellt. Dazu gehören die Raupengeometrie, die Überlappung einzelner Raupen, die Verwendung unterschiedlicher Aufbaustrategien und die Teilung des Gesamtkörpers in Teilkörper. Der Zielkonflikt wird durch die Herstellung von Probekörpern mit unterschiedlichen Steigungswinkeln an den Seitenflächen verdeutlicht. Die Ergebnisse zeigen eine verbesserte Endformnähe in Bereichen flacher Steigung beim Einsatz kleiner Schweißraupen. Im Vergleich dazu erlauben die Schweißparameter der großen Raupen eine 5-fach höhere Aufbaurate. Bei einer Raupenüberlappung kleiner und großer Raupengeometrien innerhalb einer Lage treten Anbindungsfehler auf. Strategien zur Behebung dieses Fehlers durch Anpassung der Schweißreihenfolge werden in dieser Veröffentlichung aufgezeigt. Diese Erfahrungen werden genutzt, um einen Gesamtkörper aus Teilkörpern unterschiedlicher Raupengeometrien zu fertigen.