Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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  • Publication
    Edge Computing Software für den Zerspanungsprozess
    ( 2023)
    Uhlmann, Eckart
    ;
    Hocke, Toni
    ;
    Heper, Martin
    ;
    Polte, Mitchel
    In aktuellen Forschungsprojekten entwickeln Forscher des Instituts für Werkzeugmaschinen und Fabrikbetrieb (IWF) Open-Source-Software für Edge Devices. Für die Auslegung der Fertigungsprozesse wird neben den ingenieurwissenschaftlichen Themen auch exemplarisch die Auslegung einer entwickelten Auswerteelektronik inklusive der Softwarebereitstellung adressiert. Der interdisziplinäre Ansatz, einschließlich der Softwarebereitstellung, wird exemplarisch an einem DFG-Projekt zur Prozessüberwachung bei der Ultrapräzisionsdrehbearbeitung diskutiert.
  • Publication
    Echtzeit-Energieüberwachung in der Funkenerosion
    ( 2023)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Yabroudi, Sami
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    Thißen, Kai
    ;
    Penske, Wilhelm
    Ein großes Optimierungspotenzial der Funkenerosion liegt in den Energien der einzelnen Entladungen verborgen. Eine vektorielle Bestimmung der Entladedauern und die darauf basierende Energieberechnung sowie Klassifizierung erlauben es, die Entladeenergien, Entladungsarten und -dauern in Echtzeit zu überwachen und zu analysieren. Möglich wird dies durch ein Multiprocessing-Erzeuger-Verbraucher-Schema, welches überdies eine Visualisierung und Auswertung der Messdaten erlaubt.
  • Publication
    Novel Advances in Machine Tools, Tool Electrodes and Processes for High-Performance and High-Precision EDM
    ( 2022)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Yabroudi, Sami
    High-performance electrical discharge machining (EDM) is a key technology for manufacturing high-precision components in a broad range of industrially relevant applications. Formation of debris in the working gap leads to arcing and short-circuits on the surface as well as related inaccuracies and process instabilities. Despite decades of research in the field of EDM excessive tool wear and limited process performance are still challenging. In order to overcome highly complex state-of-the-art challenges, dedicated processes, machine tools, peripheral systems, software, tool electrodes and technologies for the application of alternative dielectric fluids have been developed. Within this work novel advances in the development of a sophisticated dry EDM machine tool, including generator and process control technology based on open architecture, open source software, and commonly available machine tool components, are presented. Solutions for challenges regarding remaining debris and gas bubbles as well as related arc discharge and short-circuit pulses in sinking EDM are presented by new flushing methods, technologies and devices. A new system for inverted pressure flushing of a dielectric fluid in ED-drilling enables a highly efficient removal of debris and gas bubbles through the interior channels of the tool electrode. A new multi-luidic spindle system for EDM provides the ability to use performance- and material-related application of gaseous, near-dry and liquid dielectric fluids sequentially within a single machining process. Recent advances in tool electrode design, tool electrode material application, modification and production have led to essential process improvements. A helical tool electrode design significantly improved flushing conditions and related material removal rate in ED-drilling. Modification of ED-drilling tool electrode surfaces by thermal oxidation of copper reveals a promising approach to minimize ineffective discharges. Application of a specific mesophase-pitch carbon fiber with a diameter of df = 10 µm using a new process and handling technology enabled drilling holes with a diameter of dh = 25 µm. Next to the shown advances in EDM, efficient development of new process technologies could be enabled by using a specially adapted natural analogue algorithm software tool.
  • Publication
    High-Performance Electro-Discharge Drilling with a Novel Type of Oxidized Tool Electrode
    ( 2022)
    Uhlmann, Eckart
    ;
    Polte, Julian
    ;
    Streckenbach, Jan
    ;
    Dinh, Ngoc Chuong
    ;
    Yabroudi, Sami
    ;
    Polte, Mitchel
    ;
    Börnstein, Julian
    Electro-discharge drilling is a key technology for manufacturing sophisticated nozzles in a broad range of automotive and aerospace applications. The formation of debris in the working gap leads to arcs and short circuits on the lateral surface when state-of-the-art tool electrodes are used. As a result, limited drilling depth, increased linear tool wear, and the conicity of boreholes are still challenges. In this work, a new approach for the passivation of the lateral surface of copper tool electrodes by oxidation is shown. The comparison with state-of-the-art tool electrodes showed a reduction in the erosion duration by 48% for machining hardened steel. Promising improvements could be achieved by the thermal oxidation of the tool electrodes with the aim of increasing the electrical resistivity of the lateral surface of the tool electrode. However, due to the loss of strength, the high oxide layer thickness, and the partial delamination of the oxide layer, further comprehensive investigations on the influence of the oxidation temperature need to be conducted. Future adjustments with lower oxidation temperatures will be carried out.
  • Publication
    Comparing the performance of a nested to a continuous evolution strategy with covariance matrix adaption for optimization of drilling EDM
    ( 2022)
    Uhlmann, Eckart
    ;
    Streckenbach, Jan
    ;
    Polte, Mitchel
    ;
    Osmanovic, M.
    ;
    Schick, F.
    Electrical discharge machining (EDM) is a complex manufacturing process where the correlation of the individual process parameters is not fully known. When introducing new materials or complex, individual geometries in EDM, a satisfactory vector of parameters for the process must be found. This challenge is often encountered in the aerospace industry as well as in mold and tool making. One previously successful method to tackle this challenge is the stochastic optimization procedure Evolutionary Strategy (ES). Utilizing an appropriately chosen objective function, the search for a suitable vector of input parameters may be formulated as a mathematical minimization problem over the parameter space. The ES with a covariance matrix adaption (CMA) was utilized to sample from this parameter space in a stochastic manner. Examining the impact of the CMA within an ES is a promising way to gain better insight into the performance of ES. For this purpose, a vector of input parameters was optimized for a drilling EDM process with a comma and a nested comma ES with CMA. It was found that the comma ES led to a reduction in erosion duration tero of 38 % compared to the initially chosen parameters and the nested comma ES led to a reduction in erosion duration tero of 27 % compared to the same initial parameters. The additional information stored in the covariance matrix enables the ES to find a local optimum of the parameter vector faster and more consistently. This fact is verified by use of visualizations of the covariance matrix on a two-dimensional subspace. From these findings it can be concluded, that for the application of the ES to the optimization of EDM processes the CMA should be performed continuously over all generations as opposed to resetting this matrix after a number of generations.
  • Publication
    Investigation of additive manufactured tungsten carbide-cobalt tool electrodes for sinking EDM
    ( 2022)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Hörl, Robert
    ;
    Braun, Thomas
    ;
    Bolz, Robert
    Increasing product complexity and continuous developments in related tool and mould making industry require ongoing advances in manufacturing processes like electrical discharge machining (EDM). To meet the increasing requirements, the development of adapted EDM processes and tool designs is necessary. Additive manufacturing (AM) enables the manufacturing of complex tool electrode geometries with interior flushing channels for EDM processes with very few restrictions regarding the design. This accounts even for tungsten carbide-cobalt (WC-Co), which is a suitable material for EDM tool electrodes with various advantages, e.g. thermal and mechanical stability. This paper shows first results of additive manufactured WC-Co tool electrodes for the use in sinking EDM and the related development process.
  • Publication
    Simulativer Vergleich tubularer Peltierelemente
    ( 2022)
    Binninger, Roland
    ;
    Pernau, Hans-Fridtjof
    ;
    Schäfer-Welsen, Olaf
    ;
    Triebel, Florian
    ;
    Polte, Mitchel
    ;
    Uhlmann, Eckart
    Der Einsatz von Peltierelementen bietet in der Temperierung von Prozessen und Bauteilen einen großen Vorteil gegenüber der in technischen Anwendungen üblicherweise eingesetzten Fluidkühlung. Sie pumpen Wärme rein elektrisch und stellen Temperaturen sehr schnell sowie präzise ein. Für eine neuartige, thermoelektrisch temperierte Motorspindel wurden in Kooperation zwischen dem Fraunhofer-Institut für Physikalische Messtechnik IPM und dem Institut für Werkzeugmaschinen und Fabrikbetrieb IWF der Technischen Universität Berlin zwei unterschiedliche Ansätze tubularer Peltierelemente simulativ verglichen. Die Ergebnisse zeigen, dass es mit beiden Konzepten möglich ist, induzierte Wärmeströme am Lagersitz abzu­führen, um diesen auf eine vorgegebene Temperatur zu regeln.
  • 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
    Characterization and investigation of binderless nanopolycrystalline diamond turning tools for precision machining
    ( 2022)
    Uhlmann, Eckart
    ;
    Sturm, Heinz
    ;
    Polte, Mitchel
    ;
    Hocke, T.
    ;
    Polte, C.
    ;
    Polte, Julian
    Cemented carbide is used in a wide range of industrial applications as a wear-resistant material, e.g. in mould making and forming industry. At state of the art, the machining of cemented carbide is severely limited because of the hardness, high strength and the resulting wear resistance of the material. Due to the brittle-hard character cemented carbide materials suffer from surface cracks during the machining. The brittle-hard character and the related phenomena result in high tool wear. A promising approach for the machining of cemented carbide is the use of the novel cutting material binderless nanopolycrystalline diamond (NPD) with a dedicated cutting edge design. Within this work, laser machined tools with a corner radius of rε = 400 µm are fully characterized, investigated by Raman spectroscopy regarding the condition of the diamond and applied for first cutting experiments. Cutting investigations were carried out using specimens with a tungsten carbide content of cC = 88 %, a cobalt content of cCo= 12 % and a grain size of dg= 0.5 µm. Prior to these investigations, the condition of the diamonds and possible changes due to the lasered cutting edges were examined by Raman spectroscopy. During the cutting investigations, the brittle-ductile transition as well as the minimum chip thickness were identified by scratching tests. It could be shown that a hydrostatic stress state can be used to achieve ductile chip formation using cemented carbide as workpiece material.
  • Publication
    Zirconium dioxide-reinforced aluminium oxide ceramic for micro-milling of graphite
    ( 2022)
    Uhlmann, Eckart
    ;
    Polte, Mitchel
    ;
    Polte, Julian
    ;
    Hocke, T.
    ;
    Wendt, M.
    Tool and mould making is one of the most important sectors for production of complex parts with highest economic efficiency. Particularly the milling process is a key technology for the manufacturing of tool electrodes for electrical discharge machining (EDM). Beside copper, graphite is the most industrial relevant tool electrode material for sinking-EDM. According to the state of the art the machining of graphite results in high tool wear in consequence of strong chemical and abrasive effects. Currently, uncoated and cost intensive diamond coated cemented carbide tools are used for industrial applications. High tool costs and short tool life have a negative impact on the economic efficiency of the manufacturing process and increase the overall production costs. To reduce the production costs, the needs for innovative cutting materials and dedicated manufacturing processes are high. The zirconium dioxide-reinforced aluminium oxide ceramic used in this investigation shows a great potential because of the high hardness H, the missing binder phase and the covalent bond. The aim of this investigation is the examination of the application behaviour of ceramic cutting tools during the machining process of graphite. Therefore, dedicated milling tests in partial and full cut were carried out. For evaluation of the application behaviour of the ceramic tools, the surface quality of the machined graphite depending on the wear of the tools was considered. The results show that a minimum surface roughness of Ra = 0.80 µm and average surface roughness of Rz = 6.55 µm could be achieved in first milling tests. Due to a strong sharpening effect of the cutting edge during the machining, the possibility was provided to produce complex components with highest precision and without chipping behaviour. The machining of graphite using ceramic milling tools shows extensive advantages compared to conventional milling tools, which may positively affect the economic efficiency of machining graphite in the future.