Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Effects on the distortion of Inconel 718 components along a hybrid laser-based additive manufacturing process chain using laser powder bed fusion and laser metal deposition
    ( 2021)
    Uhlmann, E.
    ;
    Düchting, J.
    ;
    Petrat, T.
    ;
    Krohmer, E.
    ;
    Graf, B.
    ;
    Rethmeier, M.
    The combination of laser powder bed fusion (LPBF), 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 additive manufacturing times for large metallic parts. For the industrial application of the LPBF-LMD hybrid process chain, it is necessary to investigate the influence of the LMD process on the LPBF substrate. In addition, the build plate material also has a significant impact on the occurrence of distortion along the additive manufacturing process chain. In the literature, steel build plates are often used in laser-based additive manufacturing processes of Inconel 718, since a good metallurgical bonding can be assured whilst reducing costs in the production and restoration of the build plates. This paper examines the distortion caused by LMD material deposition and the influence of the build plate material along the hybrid additive manufacturing process chain. Twin cantilevers are manufactured by LPBF and an additional layer is subsequently deposited with LMD. The distortion is measured in the as-built condition as well as after heat treatment. The effect of different LMD hatch strategies on the distortion is determined. The experiments are conducted using the nickel-base alloy Inconel 718. The results show a significant influence of LMD path strategies on distortion, with shorter tool paths leading to less distortion. The remaining distortion after heat treatment is considerably dependent on the material of the build plate.
  • Publication
    Thermal and technological aspects of double face grinding of Al2O3 ceramic materials
    ( 2019)
    Deja, M.
    ;
    List, M.
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    Lichtschlag, L.
    ;
    Uhlmann, E.
    Double face grinding with planetary kinematics is a process to manufacture workpieces with plan parallel functional surfaces, such as bearing rings or sealing shims. In order to increase the economic efficiency of this process, it has to be advanced permanently. The temperature in the contact zone of most grinding processes has a huge influence on the process efficiency and the workpiece qualities. In contrast to most grinding processes these influences are unknown in double face grinding with planetary kinematics. The application of standard measuring equipment is only possible with high effort due to the inaccessibility of the working space during the machining process. Furthermore, measurement of the workpieces temperature in the considered machining system is not reported. Due to that fact, the intensive cooling has so far been the only method to avoid the occurrence of thermal defects especially in case of brittle ceramic materials. The influence of the mean cutting speed, the tools' cutting performance and the coolant flow on the temperature change of the workpieces made of Al2O3 ceramic materials was investigated with the use of a newly developed method. The first empirical approach to predict the change in temperature of the ceramic workpieces while processing is proposed. The developed measuring method can be used for obtaining experimental temperature data in other processes, such as polishing and lapping for which only theoretical models exist.
  • Publication
    Ecological and functional optimization of the pretreatment process for plasma based coatings of cutting tools
    ( 2019)
    Uhlmann, E.
    ;
    Riemer, H.
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    An, S.
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    Fröhlich, M.
    ;
    Paschke, H.
    ;
    Petersen, M.
    Increasing demands in machining of high-tech materials and dry machining lead to higher thermal and mechanical loads on cutting tools. In response to these challenges, enhanced coating solutions are applied to increase performance and life of cutting tools. However, during the production process the cemented carbide substrates are contaminated with grinding oils and residues of organic material. For the subsequent physical vapor deposition (PVD) coating process an intensive and high-quality cleaning process is necessary. In this contribution, plasma electrolytic polishing (PEP) is used as a novel alternative to conventional ecologically harmful cleaning baths. Apart from the ecological advantage, the surface of the substrate can be optimized with regard to the coating adhesion. To examine the performance of the different cleaning processes, machining tests were performed at the IWF to evaluate the layer adhesion and tool life of the tools.
  • Publication
    CVD-Diamantwerkzeuge mit SiC-Zwischenschicht
    ( 2019)
    Uhlmann, E.
    ;
    Barth, E.
    ;
    Gäbler, J.
    ;
    Höfer, M.
    Der Cobalt-(Co)-Anteil in Hartmetallen diffundiert während des Diamantbeschichtungsprozesses in die Diamantschicht und mindert deren Haftfähigkeit. Siliciumcarbid-(SiC)-Zwischenschichten können als Diffusionsbarriere für Cobalt dienen und die konventionelle Ätzvorbehandlung der Substrate ersetzen. Im Rahmen einer Forschungsarbeit werden Beschichtungsprozesse mit SiC-Zwischenschicht entwickelt, diese Schichtsysteme auf verschiedene Substrate aufgebracht und durch Zerspanungsuntersuchungen bewertet.
  • Publication
  • Publication
    Reconfiguring machine tool behavior via smart building block systems
    ( 2019)
    Uhlmann, E.
    ;
    Peukert, B.
    The reconfigurability of manufacturing systems is conventionally increased by utilizing concepts of modularization and platforms. At this moment, the actual reconfigurability is often limited to a priori designed reconfiguration variants for the production within single part families. There is only a little research on reconfiguring the mechanical behavior of machine tool frames. This paper presents an innovative approach for reconfiguring the mechanical behavior based on smart building block systems. Topologically optimized polyhedral building blocks are mechanically bolted to form different machine tool frame configurations. A high grade of modularization allows for the assembly of individualized topologies for different manufacturing scenarios "as needed when needed". The increase in reconfigurability results from the high geometric flexibility of the proposed building block system. However, successful implementation relies on quick and robust simulation approaches for calculating the machine tool frame characteristics before the actual assembly process. Within this paper, a time-efficient approach based on the sub-structuring methodology is utilized. The presented approach consists of forming superelements by performing a GUYAN reduction on the building blocks to extract the stiffness behavior. A Component Mode Synthesis is used to extract modal information. The ANSYS Parametric Design Language is then used to automatically couple the modules according to a customized descriptive machine tool language. A simple joint model is implemented and experimentally fitted with a two-block configuration. The two-block configuration is then extrapolated to a full machine tool frame portal. An example of changing the modal characteristics of this machine tool frame portal is presented in the form of numerical results.
  • Publication
    Ultrasonic assisted peripheral milling of fiber reinforced plastics in consideration of clamping and cutting edge geometry
    ( 2019)
    Uhlmann, E.
    ;
    Protz, F.
    In the field of machining fiber reinforced plastics (FRP) with defined cutting edges, there is still a high demand for research and development, especially, when various fiber types are embedded. Thus, when machining glass fiber reinforced plastics, the application of uncoated tools from tungsten carbide is often state of the art. This material is subject to excessive wear during machining FRP, which negatively affects the process performance and makes a regular tool change necessary. This is caused by a high abrasiveness of the fibers and by vibrations of the FRP components, which affects the cutting edge. One approach to reduce the process forces and therefore reduce tool wear is to superimpose the tool movement with a longitudinal high-frequency movement in ultrasonic range. Many studies showed that this technology is able to generate advantages in drilling and face milling processes. Primarily it reduces tool wear and improves machining quality. This study shows that positive effects also occur during peripheral milling of FRP, especially when using an unstable clamping. In this case, ultrasonic assistance can reduce the machining forces significantly. Additionally, it is shown that the shape and the state of wear of the cutting edge affects the impact of ultrasonic assistance in this application case.
  • Publication
    Elektromechanisches Glattwalzen von Stahllegierungen
    ( 2019)
    Uhlmann, E.
    ;
    Thom, S.
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    Prasol, L.
    ;
    Haberbosch, K.
    ;
    Drieux, S.
  • Publication
    Modelling of Abrasive Water Jet Cutting with Controlled Depth for Near-Net-Shape Fabrication
    ( 2019)
    Uhlmann, E.
    ;
    Männel, C.
    Near-net-shape fabrication of difficult to machine materials is a promising application for the abrasive water jet technology. An effective implementation can be achieved by controlling the kerf depth and cutting off defined material fragments. A model for controlled cutting is introduced to make the machining process design more effective for different materials. An empirical model was combined with the process' physical behavior, allowing the prediction of the kerf geometry using a minimum number of predictors and thus initial trials. The model tested with metal matrix composites, reveals the capability of transferring knowledge to new materials using few initial trials.