Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Sensor integration in hybrid additive manufactured parts for real-time monitoring in turbine operations
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Kersting, Robert
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    Brunner-Schwer, Christian
    ;
    Neuwald, Tobias
    Real-time monitoring of operation conditions such as tempeatures and vibrations enables efficiency enhancement for maintenance tasks. In energy industry monitoring of critical components such as turbine blades is essential for the operation safety. But the effective recording of critical process data is a challenging task due to the extreme operating conditions. With a hybrid processing approach combining two additive manufacturing technologies new classes of self-monitoring components become possible allowing data acquisition directly inside the component. Using the example of a turbine blade, the hybrid process chain is described. The turbine blade blank is produced via Laser Powder Bed Fusion (L-PBF) with channels for the integration of high temperature sensors. After integration cavities were closed by Laser Directed Energy Deposition (L-DED) followed by classical milling operations for part finishing. The data acquisition is integrated in state-of-the-art product l ifecycle monitoring (PLM) software to create a digital twin. Evaluation shows that temperature could be successfully monitored at conditions of Π= 550°C.
  • Publication
    Precision finishing of additively manufactured components using the immersed tumbling process
    ( 2021)
    Polte, Julian
    ;
    Polte, Mitchel
    ;
    Hocke, Toni
    ;
    Lahoda, Christian
    ;
    Uhlmann, Eckart
    Additive manufacturing enables the production of highly complex metallic components with highest geometrical flexibility in dedicated lightweight construction. For titanium-aluminium alloys, which are used in particular in the aviation industry, powder bed based processes such as the laser powder bed fusion are established. Nevertheless, laser powder bed fusion is limited with regard to the producible surface roughness in a range of 5 µm ⤠Ra ⤠15 µm. According to the state of the art, the increase of the geometrical accuracy and the reduction of the surface roughness values of the additive manufactured components are realised by different cutting and non-conventional processes. In this investigation, a new approach for the reduction of the surface roughness values by immersed tumbling was realised. Therefore, additively manufactured square bars made of the titanium alloy Ti-5Al-5Mo-5V-3Cr were used as sample geometries. An immersed tumbling machine tool with plan etary kinematics for post-processing was applied and the lapping media QZ, HSC 1/500 and M5/400 were evaluated. In addition, the influence of the rotor speed and the holder as well as the depth of immersion were considered as influencing factors. As target values the surface roughness values as well as the rounded edge radius were examined. Within this investigations the surface roughness values could be reduced by more than 90 %. In addition, a targeted rounding of the edges could be obtained, which removed the excess edge height at the part resulting from the laser powder bed fusion process. As a result the immersed tumbling process shows a great suitability as a finishing process for additively manufactured components and is particularly suitable for automated and serial finishing processes.
  • Publication
    Investigation on laser cladding of rail steel without preheating
    ( 2021)
    Brunner-Schwer, Christian
    ;
    Biegler, Max
    ;
    Rethmeier, Michael
    The contact between train wheels and rail tracks is known to induce material degradation in the form of wear, and rolling contact fatigue in the railhead. Rails with a pearlitic microstructure have proven to provide the best wear resistance under severe wheel-rail interaction in heavy haul applications. High speed laser cladding, a state-of-the-art surface engineering technique, is a promising solution to repair damaged railheads. However, without appropriate preheating or processing strategies, the utilized steel grades lead to martensite formation and cracking during deposition welding. In this study, laser cladding of low-alloy steel at very high speeds was investigated, without preheating the railheads. Process speeds of up to 27 m/min and laser power of 2 kW are used. The clad, heat affected zone and base material are examined for cracks and martensite formation by hardness tests and metallographic inspections. A methodology for process optimization is presented and the specimens are characterized for suitability. Within the resulting narrow HAZ, the hardness could be significantly reduced.
  • Publication
    Micro-milling of a sprue structure in tungsten carbide-based metal matrix composite
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Polte, Mitchel
    ;
    Hein, Christoph
    ;
    Hocke, Toni
    ;
    Jahnke, Christian
    Many industries rely on plastic components manufactured by micro-injection moulding. There is a high potential to further increase the cost-effectiveness by machining the moulds needed for this process from non-ferrous metals and reinforcing the parts of the mould, which experience high loads during the micro-injection moulding. Inserting tungsten carbide particles locally into the surface of these non-ferrous metals is one possibility of reinforcement. The resulting metal-matrix-composites (MMC) exhibit the needed wear resistance, while the ground material can be machined very effectively through micro-milling. In contrast, the Micro-milling of these MMC-materials is challenging and so far not state of the art. Thus, this investigation is concerned with the development and qualification of micro-milling parameters for tungsten carbide-based MMC-materials. Binderless polycrystalline diamond as innovative cutting material was applied for this purpose. The goal of the mil ling parameter development was to optimize the surface roughness and the form accuracy for machining an aluminium bronze workpiece reinforced with tungsten carbide particles through laser injection. Based on an analysis of a wide range of process parameters, an optimised milling strategy was applied to machine a sprue structure from the described MMC-material. Different parameter sets are evaluated by analysing the form accuracy and measuring the surface roughness of machined structures. A surface roughness of Ra = 80 nm and form accuracy of a = 3 µm could be achieved with optimized micro-milling parameters and qualified the developed parameters for industrial applications.
  • Publication
    Tool wear and surface roughness in micro-milling of aluminium and high-alloyed aluminium materials using cutting tools made of binderless carbide
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Wiesner, H.M.
    ;
    Polte, Julian
    ;
    Hein, Christoph
    Micro-milling can be applied for manufacturing in a wide range of materials and complex geometries. This process is especially important for the aerospace industry. High-alloyed aluminium is a common material for aerospace applications with complex micro- and macro-geometry due to its high wear resistance. The costs-effectiveness of producing these parts can be increased by using tools with improved wear behaviour and higher life times. However, wear-resistant tools are often associated with higher tool costs, which reduces the cost-effectivness of the whole production. An innovative solution is offered by the use of a cutting tool made of binderless tungsten carbide. The micro-milling of conventional and high-alloy aluminium with a new cutting material based on a binderless tungsten carbide is analysed in this investigation. The absence of a binding phase leads to an increased hardness and improves the wear behaviour of these tools. Therefore, tools with a tool diamete r of D = 10 mm were manufactured and there machinability was successfully proven. The feasibility of these innovative tools is demonstrated in a series of experiments. The experimental investigations were carried out on the five-axis high precision machine tool PFM 4024-5D PRIMACON GMBH, Peißenberg, Germany, with a workpiece made of TiAl 48-2-2. A surface roughness of Ra = 0.202 µm was detected after a path length due to primary motion lc = 70 m without any noticeable wear marks on the cutting tool. These results show the economic potential for milling tools based on binderless carbide for achieving high precision surfaces while reaching high lifetimes.
  • Publication
    How Pedestrians Perceive Autonomous Buses: Evaluating Visual Signals
    ( 2021)
    Brandenburg, Elisabeth
    ;
    Kozachek, Diana
    ;
    Konkol, Kathrin
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    Woelfel, Christiane
    ;
    Geiger, Andreas
    ;
    Stark, Rainer
    With the deployment of autonomous buses, sophisticated technological systems are entering our daily lives and their signals are becoming a crucial factor in human-machine interaction. The successful implementation of visual signals requires a well-researched human-centred design as a key component for the new transportation system. The autonomous vehicle we investigated in this study uses a variety of these: Icons, LED panels and text. We conducted a user study with 45 participants in a virtual reality environment in which four recurring communication scenarios between an autonomous driving bus and its potential passengers had to be correctly interpreted. For our four scenarios, efficiency and comprehension of each visual signal combination was measured to evaluate performance on different types of visual information. The results show that new visualization concepts such as LED panels lead to highly variable efficiency and comprehension, while text or icons were well ac cepted. In summary, the authors of this paper present the most efficient combinations of visual signals for four reality scenarios.
  • Publication
    Concept for an actuated variable tool electrode for use in sinking EDM
    ( 2021)
    Uhlmann, Eckart
    ;
    Streckenbach, Jan
    ;
    Thißen, Kai
    ;
    Schulte Westhoff, Bela
    ;
    Masoud, Abd Elkarim
    ;
    Maas, Jürgen
    Typically, a large number of individual tool electrodes has to be used in sinking electrical discharge machining (sinking EDM) to successfully machine a single workpiece. Due to non-uniform wear and insufficient flushing of the working gap electrode geometries have a significant effect on the process efficiency. This paper discusses the use of an actuated variable tool electrode for sinking EDM to reduce the number of required tool electrodes and to increase the overall process efficiency. A miniaturised linear actuator was developed to individually move electrode segments to form the target shape for the tool electrode. The coordinated actuation of bundled electrode segments introduces new methods for the active flushing within the working gap, which cannot be implemented in conventional sinking EDM. Intelligent sinking strategies can further improve process efficiency by creating and sinking sub-geometries into the workpiece offering improved flushing conditions compa red to the original geometry.
  • Publication
    Simulating flow behaviour of wet particles within the immersed tumbling process
    ( 2021)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Kuche, Yves
    ;
    Landua, Fabian
    For many production chains, it is mandatory to involve special finishing of the manufactured parts for the chipping of the edges as well as the polishing of surfaces. One commonly used method is the immersed tumbling process, where any workpiece is dragged through a particle filled container. In many cases, the immersed tumbling process operates in environments with added liquids, leading to changes in particle-tool interaction and general flow behaviour of the used particles. Whilst the discrete element method for simulating particles is mainly limited to dry particles, the used software ROCKY DEM from ESSS, Florianópolis, Brasil, comes with a built-in liquid-bridge model to simulate water-covered particles and granulate and furthermore an extension for system couplings with Ansys Fluent of the company ANSYS, INC., Canonsburg, Pennsylvania. The latter can be used to create from both software one three-phase-model with higher amounts of actually simulated water. In thi s study, small amounts of water were added to differently shaped particles using the build-in liquid-bridge model, to analyse and compare the particles flow characteristics in both, wet and dry environments. To gather significant information leading towards precise comparisons, the particles trajectories, velocities and resulting forces against the workpieces can be specifically observed and analysed, whilst this kind of process knowledge could previously never been taken into account without simulation.
  • Publication
    Towards a Framework for Impact Assessment of Research & Technology Organisations
    ( 2021)
    Kidschun, Florian
    ;
    Hecklau, Fabian
    Due to their ability to bridge the gap between knowledge created by basic research and market requirements, Research and Technology Organisations (RTOs) play a major role in countriesâ innovation systems. Their R&D results should lead to innovations, which in turn generate the economic output of public investment in research and development. Moreover, they should support the foundation of new companies and industrial innovations. RTOs can thus be seen as intermediaries between R&D and the industry, while they themselves constitute to a certain extent entrepreneurs and actors in applied R&D that focus on industrial and commercial application right from the start of their activities. Therewith, RTOs pursue to increase the competitiveness of the entire economy. With a growing demand for evaluating their actual contribution in national innovation systems, simply stating the goal of positive impact to stakeholders like governments, the public, investors etc. is not enough; its accomplishment needs to be proven by robust evidence. In this regard, the value of an impact assessment is determined by the strength of the evidence produced and the credibility of the evaluation. RTOâs research activities and their impacts are diverse in nature and occur across many sectors of the economy. To gain transparent insights into relevant and comprehensive performance metrics showing the impact of RTOs from a micro- and macroeconomic perspective, impacts are only appropriate for evaluation if a causal relationship can be drawn back to their origin. While some impacts are primarily economic and suitable for quantitative analysis, others have to be evaluated qualitatively. Regardless of its type, each impact needs to be assessed within a common framework to enable a comprehensive understanding of RTO's impact. Within this contribution, an impact assessment framework is established with the aim to enable the identification of causal relationships between impacts and their origin.
  • Publication
    Time-Sensitive Networking over Metropolitan Area Networks for Remote Industrial Control
    ( 2021)
    Tschöke, Simon
    ;
    Lynker, Frederic
    ;
    Buhr, Hauke
    ;
    Schreiner, Florian
    ;
    Willner, Alexander
    ;
    Vick, Axel
    ;
    Chemnitz, Moritz
    The benefits of the currently evolving IEEE Time-Sensitive Networking (TSN) standard have already been globally recognized. Whereas the application of TSN in a LAN is currently widely and globally tested, TSN in a Metropolitan Area Network (MAN) has not been a major focus until now. The possible benefits of utilizing co-located Edge Clouds in order to support multiple urban production sites with industrial realtime applications open a wide range of new business models. Therefore, we have analyzed the feasibility of transparently using PROFINET over TSN via a Dense Wavelength Division Multiplex (DWDM) link, where a machine park is controlled remotely by an Edge-based virtual Programmable Logic Controller (vPLC). As a result, we are able to setup a TSN connection over a MAN with a one-way delay of about 156.5 J.ms and a jitter of about 12 ns. This work can be extended to allow for dynamically provisioned TSN flows and multi-path Frame Replication and Elimination (FRER) for distributed hard real-time machine control and adoption to Ultra-Reliable Low-Latency Communication (URLLC) 5G campus networks.