Now showing 1 - 10 of 560
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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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Application of laser surface nanotexturing for the reduction of peri-implantitis on biomedical grade 5 Ti-6Al-4V dental abutments

2019 , Uhlmann, E. , Schweitzer, L. , Cunha, A. , Polte, J. , Huth-Herms, K. , Kieburg, H. , Hesse, B.

The annual revenue of dental implants is estimated on 33 billion USD in 2019 and the efforts to keep the teeth functionality and aesthetics is continuously growing over the years. However, loosening of dental implants induced by infection is still a critical and common problem worldwide. In this scenario, the development of new implant manufacturing strategies is of utmost importance. Every surface exposed in the oral cavity, both the tooth and the implant surface, are covered by a layer of salivary proteins, the so-called pellicle. The initial formation of a pellicle is followed by the attachment of bacterial cells onto it. Well-developed biofilms on dental implant surfaces become the main source of pathogenic microbes causing Peri-Implantitis, which is one of the main causes of dental implant failure. The surface topography and chemical composition of an implant are key factors in controlling surface wettability, which directly affects the formation of the biological films. In this sense, ultrafast laser surface nanotexturing rises as a promising advanced technology for controlling implant surface biological properties. Laser-processing parameters such as laser wavelength l, fluence F and number of pulses N are essential for surface texturing. Thus, this paper presents promising results on the influence of different laser induced periodic surface structures (LIPSS) on the composition of the pellicle and the biofilm formation on biomedical grade 5 Ti-6Al-4V dental abutments. Moreover, a biofilm reactor was built and adapted to assess the effect of the LIPSS on the biofilm formation.

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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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Hochleistungsbohrwerkzeuge für CFK

2019 , Uhlmann, E. , Christiansen, G. , Reimers, W. , Brömmelhoff, K.

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Verfügbarkeitssteigerung durch gezielte Datenanalyse

2020 , Uhlmann, E.

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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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Einsatzverhalten von CVD-Diamantdünnschichtwerkzeugen

2019 , Uhlmann, E. , Hinzmann, D.

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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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Cutting force prediction in micro-milling considering the cutting edge micro-geometry

2019 , Uhlmann, E. , Polte, J. , Wiesner, H.M. , Kuche, Y. , Polte, M.

The micro-milling process is used for a wide range of materials and enables the manufacturing of complex geometries with micro-features. One important factor for the tool life is the cutting force Fc, which depends on the applied technology, process parameters and cutting edge micro-geometry. High cutting forces Fc can lead to tool breakage in the transition between the shank and the cutting part of cemented carbide end mills. The prediction of cutting forces Fc in micro-milling processes through cutting force models could potentially decrease the hazard of tool breakage. By including the cutting edge radius rv into the prediction model, additional correction factors can be avoided. Therefore, further knowledge about the applicability of those models for the micro-milling process with chip thickness h < 0.01 mm is needed. In this investigation, the cutting force model of KOTSCHENREUTHER [1], which takes the cutting edge radius rv into account is used for the cutting force prediction in micro-milling. In order to validate this model, an innovative lead free copper alloy CuZn21Si3P is machined. Cemented carbide micro-milling tools with tool diameter D = 1 mm were used. The manufacturing of different cutting edge radii rv was realised with the immersed tumbling process. During milling experiments with a five-axis high precision machine tool the cutting forces Fc were measured. Cutting forces in a range of 6 N < Fc < 26 N were detected. The results show good correlations between the predicted and experimental determined cutting forces Fc. Furthermore, the measured cutting edge radii rv show a high influence on the deviation of the measured and predicted cutting forces Fc.

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Nachbearbeitung additiv gefertigter Titanbauteile - Potentiale des Fliehkraftgleitschleifens

2019 , Uhlmann, E. , Eulitz, A. , Seiffert, K. , Kersting, R. , Schenk, S.

Additive manufactured parts can be post-processed by centrifugal disc finishing as bulk. The choice of suitable media is of high importance for economic post-processing. In this paper, topography and shape changes of machined workpieces are investigated and a multistage process for post-processing additive manufactured Titanium parts is developed.