Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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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.

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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.

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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.

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Replication of Functional Surfaces Micro-Structured by EDM

2022 , Uhlmann, Eckart , Polte, Mitchel , Ludwig, Jonas , Bolz, Robert

Functional surfaces are applied in a broad range of industries ranging from automotive over aerospace to medical technology. In this paper, the manufacturing of molds micro-structured by sinking electrical discharge machining (sEDM) and the surface replication on polycarbonat (PC) is discussed. The presented analysis shows the ability to replicate hydrophobic and hydrophilic effects on PC samples from micro-structured molds fabricated by sEDM.

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Echtzeit-Energieüberwachung in der Funkenerosion

2023 , Uhlmann, Eckart , Polte, Mitchel , Yabroudi, Sami , 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.

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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.

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Precision Finishing of Additive Manufactured Ti-Al-components Using Diamond Slide Burnishing

2022 , Polte, Julian , Polte, Mitchel , Lahoda, Christian , Uhlmann, Eckart

Due to the increasing importance of lightweight design in terms of resource management, titanium aluminium (Ti-AI) alloys are gaining more and more significance. To fully exploit light weight design potentials additive manufacturing (AM) has the ability to shift state of the art product design towards maximised resource efficiency and physically minimized weight. Next to material standardization and qualification processes, major limitations for mass scale industrialization of additive manufacturing are high surface roughness values in a range of 5 μm ≤ Ra ≤ 15 urn and remaining tensile residual stress states. A promising approach to overcome these challenges shows a process chain consisting of near-net-shape laser powder bed fusion (LPBF) and subsequent finishing using a dedicate diamond slide burnishing (DSB) process [1]. Within this work plastic deformation induced by DSB and the effects on the workpiece material properties were investigated.

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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.

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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.

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Fundamental study on embedded displacement sensor arrays for ultrasonic-assisted ultraprecision machining

2022 , Uhlmann, Eckart , Polte, Mitchel , Bulla, Benjamin , Dambon, Olaf , Dicke, Clemens , Hocke, T. , Thißen, Kai , Heper, M.

Ultraprecision machining is a key technology for manufacturing complex steel moulds with dimensional accuracies in sub-micrometer range for mass production of optical components using micro-injection moulding. According to the state of the art, during the machining of carbide-forming metals, such as steel alloys, used single crystal diamond tools suffer from excessive tool wear. In order to overcome this technological und economical limitation, ultrasonic-assisted ultraprecision machining is applied successfully in a broad range of industrial and scientifically applications. Based on the reduction of the contact time between the tool and the workpiece excessive chemical and related tribological tool wear can be avoided. Nevertheless, the cutting speed is strictly limited to deceed critical contact times. Therefore, the monitoring of the tool vibration characteristic and thus the process control is a major challenge and of current industrial and scientifically interest. To overcome these challenges a method for in-situ measurement of the ultrasonic vibration is currently being developed and first results are shown. Using the sophisticated ultrasonic system, developed by SON-X GMBH, Aachen, Germany, up to a frequency fUS= 100 kHz the application of a dedicated eddy current sensor enabled the determination of the real path lines and the exact position of the cutting edge during the whole process with a displacement amplitude AD= 1 µm. The results were subsequently verified by laser vibrometer measurements. As a result of the investigation, an elliptical path movement of the cutting edge in the longitude direction AD,y= ± 1.0 µm and in z-direction AD,z= ± 0.34 µm could be determined using a frequency fUS= 100 kHz. Based on this new measurement method, the vibration characteristic can be specifically varied and adapted to the application. In addition, a comprehensive scientifical knowledge of the process can be gained and used to improve tool wear models.

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