Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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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.

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Niobcarbid statt Wolframcarbid Alternativer Schneidstoff in der Drehbearbeitung

2019 , Kropidlowski, K. , Uhlmann, E. , Woydt, M. , Theiler, G. , Gradt, T.

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Application of niobium carbide based cutting materials for peripheral milling of CFRP

2019 , Uhlmann, E. , Meier, P. , Hinzmann, D.

Due to its inherent material properties, the implementation of niobium carbide (NbC) as hard phase in cutting materials represents a promising alternative to machining. Recent investigations show equivalent tool life in metal cutting compared with cemented carbides based on tungsten carbide (WC). Besides metal cutting, the machining of high-performance composite materials poses an increasing importance due to its growing demand in the automotive and aeronautical sector. NbC and its wear resistance against abrasion can be suitable for this specific application. Additionally, the low density of NbC indicates an advantageous dynamic behaviour. Thus, this study focuses on the milling of carbon fiber reinforced plastics (CFRP). Complex tool geometries are implemented in a peripheral milling strategy. The machining trials are conducted with uncoated NbC-based cutting materials in CFRP with varying cutting speeds vc. The utilized NbC compositions (NbC-10TiC)-6Ni7.5VC and (NbC-15TiC7N3)-5Ni7.5WC2.5Mo2C embedded in a Nickel (Ni) matrix were applied and compared towards their performance with an industrial available cemented carbide (WC-Co). As tool life criteria, a tool diameter reduction of Dd = 0.1 mm and a cutting path of lc = 10.000 mm were defined. Apart from tool life performance, the workpiece quality was assessed. An inferior performance was identified with (NbC-10TiC)-6Ni7.5VC in terms of tool life compared to WC-Co, which can be attributed to microstructure issues. Yet, (NbC-15TiC7N3)-5Ni7.5WC2.5Mo2C shows a competitive performance in machining with an achieved cutting path lc identical to WC-Co. It can be stated, that NbC-Ni systems can accomplish an equivalent performance in comparison to WC-Co when machining CFRP.

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Interaction of tool and workpiece in ultrasonic-assisted grinding of high performance ceramics

2019 , Uhlmann, E. , Bruckhoff, J.

Ultrasonic assisted grinding processes promise high potential for economical machining of brittle hard materials and improved workpiece qualities. Especially in machining of high performance ceramics as well as ceramic matrix composites (CMC) a significant decrease of process forces and increased material removal rates can be achieved. In previous publications the fundamental effect mechanisms related to ultrasonic assistance in grinding processes were described. However, implicit knowledge about the influence of the tool specifications and geometry on the maximum achievable ultrasonic amplitude is lacking. Furthermore, knowledge about the behavior of the high-frequency tool motions during tool engagement could simplify the design of ultrasonic assisted grinding processes. A targeted utilization of ultrasonic effects can be result in lower process forces, less tool wear and shorter machining times which lead consequently to more sustainable processes. The presented work provides results of the interactions of tool design, tool contact conditions and workpiece in the ultrasonic assisted machining of ceramics with mounted points.

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Verfügbarkeitssteigerung durch gezielte Datenanalyse

2020 , Uhlmann, E.

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Increasing the productivity and quality of flute grinding processes through the use of layered grinding wheels

2019 , Uhlmann, E. , Schroer, N. , Muthulingam, A. , Gulzow, B.

Due to the increasing relevance of resource efficiency, the production of cutting tools is exposed to increasing demands in regard to productivity and quality. Flute grinding is of particular significance within the various grinding operations used in tool manufacturing. Apart from the rake face, the flute grinding process determines the quality of the cutting edges. However, the grinding wheels typically used for flute grinding are not designed to take the complex contact conditions of this process into account. This paper presents a method for designing application-oriented grinding wheels to improve the productivity and the quality of grinding processes. Firstly, a model is presented which is used to simulate the contact conditions. The results show the significance of the grinding wheel edge in flute grinding. Based on that, grinding wheels with different layers over its width were developed to compensate the varying and complex contact conditions. To verify this approach technological experiments were carried out.

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Belt grinding of cast iron without cooling lubricant

2019 , Uhlmann, E. , Buelter, M.

In times of industrial globalization, the demand for more specialized and diverse product portfolios is leading to a shortage of resources. Against this background, the need for adaptable and resource-saving production processes is increasing. Belt grinding can hereby make a major contribution as one of the last steps in the production value chain. Thanks to its flexible tool system consisting of a contact element and an abrasive belt, this process can be applied to an extremely wide range of machining tasks. Recently, the great potential of diamond abrasive belts in machining high performance materials, such as Inconel, has been demonstrated. In comparison to conventional abrasive belts advantages arise over an increased tool life and higher productivity. By an appropriate choice of process parameters, it is possible to dispense with cooling lubricants due to the thermal conductivity of diamond. Consequently, the absence of expensive lubricant management periphery systems reduces health and environmental risks. The present work provides first insights into the possibilities of machining mass materials such as cast iron with diamond abrasive belts.

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3-Achs-Portalfräsmaschine als Demonstrator für ein modulares Werkzeugmaschinengestell

2019 , Uhlmann, E. , Polte, M. , Blumberg, J. , Peukert, B.

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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.

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Mikrofräsbearbeitung von MMC-Werkstoffschichten unter Einsatz von binderlosem PKD. Analyse des Einflusses der Prozessparameter auf den Mikrofräsprozess

2019 , Hein, C. , Uhlmann, E. , Polte, J. , Wiesner, H.M. , Jahnke, C. , Polte, M.

Micro-injection moulding is a key technology for the cost-effective production of plastic parts. The commonly used moulds are made of hardened steel and machined by micro-milling with coated cemented carbide tools. Today, these tools suffer from random tool breakage and excessive wear. One solution of this problem is to produce injection moulds made of non-ferrous metals and enhance them by applying a tungsten carbide matrix on the surface. Thus, this investigation addresses the micro-milling process of the resulting Metal-Matrix-Composites. Furthermore, the feasibility of binderless polycrystalline diamond as an innovative cutting material could be shown for this purpose

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