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
    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.
  • 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
    Thermal and technological aspects of double face grinding of Al2O3 ceramic materials
    ( 2019)
    Deja, M.
    ;
    List, M.
    ;
    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
    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.
    ;
    Prasol, L.
    ;
    Haberbosch, K.
    ;
    Drieux, S.
  • Publication
    Pocket milling of composite fibre-reinforced polymer using industrial robot
    ( 2019)
    Melo, E.G. de
    ;
    Klein, T.B.
    ;
    Reinkober, S.
    ;
    Gomes, J.D.O.
    ;
    Uhlmann, E.
    In the recent decades, aerospace and automotive industry are replacing metal materials by carbon fibre-reinforced polymer (CFRP). The mechanical properties of CFRP materials are very attractive due to high mechanical strength and low weight. However, there are technological challenges in the machining process for this type of material. The anisotropy and inhomogeneity of the CFRP cause high wear of the cutting tool, spalling, delamination, fuzzing, fibre pull-out, matrix cracking, thermal degradation and resulting in poor quality of the part. In addition, the requirement for processes that are more flexible within a larger work area makes the use of industrial robot (IR) a promising alternative. The present work evaluated the performance of the IR regarding motion accuracy, which influences machining conditions of composites. The trimming in a pocket milling was carried out using the factional replication of the 3k factorial design, with three levels and three factors. The tool geometry, feed rate fz and spindle speed n were selected as input parameters. In order to evaluate the robotic machining performance, resultant cutting force Fr, surface and dimensional quality were selected as output parameters to be assessed. After obtaining the force results, equations were generated for each cutting tools and Response Surface Methodology (RSM) was applied. The results show that the use of IR is a promising alternative for the CFRP machining of large aeronautical components.
  • Publication
    Mikrostrukturierte CVD-Diamant-Werkzeuge
    ( 2019)
    Bachmann, H.
    ;
    Meier, P.
    ;
    Uhlmann, E.
    ;
    Schröter, D.
  • Publication
    Tool wear modelling using micro tool diameter reduction for micro-end-milling of tool steel H13
    ( 2019)
    Manso, C.S.
    ;
    Thom, S.
    ;
    Uhlmann, E.
    ;
    Assis, C.L.F de
    ;
    Conte, E.G del
    Micro components have been demanded increasingly due to the global trend of miniaturization of products and devices. Micro milling is one of the most promising processes for micro-scale production and differs from conventional milling due to the size effect introducing phenomena like the minimum chip thickness, making the prediction of micro milling process hard. Among challenges in micro milling, tool life and tool wear can be highlighted. Understanding tool wear and modelling in micro milling is challenging and essential to maintaining the quality and geometric tolerances of workpieces. This work investigates how to model the diameter reduction of a tool caused by tool wear for micro milling of H13 tool steel. Machining experiments were carried out in order to obtain cutting parameters affecting tool wear by considering the diameter reduction. Dry full slot milling with TiAlN (titanium aluminium nitride)-coated micro tools of diameter d = 400 mm was performed. Three levels of feed per tooth (fz = 2 mm, 4 mm and 5 mm) and two spindle speed levels (n = 30,000 rpm and 46,000 rpm) were used and evaluated over a cutting length of lc = 1182 mm. The results show that lower levels of feed per tooth and spindle speed lead to higher tool wear with a total diameter reduction over 22%. The magnitude of the cutting parameters affecting tool wear was determined by ANOVA (analysis of variance), and the model validation meets the statistical requirements with a coefficient of determination R2 = 83.5% showing the feasibility of the approach to predict tool wear using diameter reduction modelling in micro milling.