Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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Nachhaltige Reinigung und Präparation

2024 , Uhlmann, Eckart , Polte, Julian , Burgdorf, Philipp , Reder, Waldemar

In der Fertigungstechnik lautet aktuell die Devise, innovative Wege für mehr Nachhaltigkeit zu entdecken. Für industrielle Reinigungsprozesse ist das CO2-Strahlen auf dem Vormarsch - im Beitrag wird beschrieben, warum.

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DEM simulation of centrifugal disc finishing

2022 , Uhlmann, Eckart , Polte, Julian , Kuche, Yves , Landua, Fabian

The finishing of small components with complex geometries is a major industrial challenge. One process that is suitable for targeted post-processing is centrifugal disc finishing with wet and dry media. In this process, the workpieces float as bulk material together with the abrasive particles in a container and are completely surrounded by the abrasive medium. As shown in previous studies, the Discrete Element Method (DEM) is suitable for investigations of grinding processes with specified workpiece motions. To simulate unpredictable workpiece motion, a new approach is being tested in which the workpieces themselves are treated as particles. Within this research paper, results for the post-processing of centrifugal disc finishing with the software ROCKY DEM are presented. The investigation results show good correlation between the numerical determined pressures and the analysis results of the rounded workpiece edges on test components made of mould-steel X13NiMnCuAl4-2-1-1.

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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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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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Semi-automatic process control for efficient refurbishment of turbine blades

2023-06-16 , Uhlmann, Eckart , Polte, Julian , Mühlich, Christopher , Mönchinger, Stephan , Ebrahimi, Puya

The refurbishment of turbine blades requires the precise removal of damaged surface coatings. In manufacturing companies, this usually involves time-consuming activities such as detecting residual coatings and adapting process settings to varying turbine blade geometries. The use of automated systems therefore opens up opportunities to improve the efficiency of turbine blade refurbishment processes by replacing manual tasks. This paper presents an conceptual approach for a semi-automatic decoating process of turbine blades that integrates abrasive blasting technology into a closed loop process control system. The experimental setup consists of a robot for guiding the turbine blade in a blast machine and a nozzle system for local removal of residual coatings using abrasive material. Based on image processing the residual coatings of a turbine blade are labeled by a neural network and mapped to a 3D model of the turbine blade, which is used by a software control system to coordinate the decoating process. Using a prototype setup this paper investigates the applicability of the proposed approach and evaluates its feasibility.

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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.

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Numerical investigation into cleanability of support structures produced by powder bed fusion technology

2022 , Campana, Giampaolo , Uhlmann, Eckart , Mele, Mattia , Raffaelli, Luca , Bergmann, André , Kochan, Jaroslaw , Polte, Julian

Purpose: Support structures used in laser powder bed fusion are often difficult to clean from unsintered powder at the end of the process. This issue can be significantly reduced through a proper design of these auxiliary structures. This paper aims to investigate preliminary the airflow within differently oriented support structures and to provide design guidelines to enhance their cleanability, especially the depowdering of them. Design/methodology/approach: This study investigates the cleanability of support structures in powder bed fusion technology. Digital models of cleaning operations were designed through computer-aided engineering systems. Simulations of the airflow running into the powder entrapped within the thin walls of auxiliary supports were implemented by computational fluid dynamics. This approach was applied to a set of randomly generated geometrical configurations to determine the air turbulence intensity depending on their design. Findings: The resul ts, which are based on the assumption that a relationship exists between turbulence and powder removal effectiveness, demonstrated that the maximum cleanability is obtainable through specific relative rotations between consecutive support structures. Furthermore, it was possible to highlight the considerable influence of the auxiliary structures next to the fluid inlet. These relevant findings establish optimal design rules for the cleanability of parts manufactured by powder bed fusion processes. Originality/value: This study presents a preliminary investigation into the cleanability of support structures in laser powder bed fusion, which has not been addressed by previous literature. The results allow for a better understanding of the fluid dynamics during cleaning operations. New guidelines to enhance the cleanability of support structures are provided based on the results of simulations.

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Smarte Überwachung elektrischer Großantriebe

2023 , Geisert, Claudio , Polte, Julian , Uhlmann, Eckart , Rauch, Hartmut , Brach, Karsten

Die Nutzung von Digitalisierungstechnologien im Kontext von Industrie 4.0 bietet insbesondere für den gesamten Bereich der Wartung und Instandhaltung von elektrischen Großantrieben großes Potenzial zur Schaffung innovativer Serviceangebote. Durch erweiterte Sensorik im elektrischen Antrieb und Intelligenz in der Verarbeitung und Analyse von Daten im Betrieb von Anlagen, kann eine vorausschauende Instandhaltungsstrategie eingeführt werden, die eine höhere Verfügbarkeit der Anlagen ermöglicht und gleichzeitig den Aufwand für Instandhaltungseinsätze reduziert. Um diese Potenziale im Servicegeschäft elektrischer Großantriebe zu erschließen, wird in diesem Beitrag ein hypothesengetriebener Ansatz zur Zustandsüberwachung beschrieben.

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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.

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Flexible Automatisierung mit Virtuellen Agenten

2022 , Uhlmann, Eckart , Polte, Julian , Mühlich, Christopher , Lindow, Kai

The process automation of hybrid assembly systems presents companies with the challenge of integrating people and machines into a collaborative system while taking socio-economic aspects into account. The transfer of biological principles to the design of production processes, in combination with Industry 4.0, enables the development of self-organizing systems. Inspired by this, a decentralized platform solution for flexible automation is presented in order to use human skills to increase productivity in a targeted manner.

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