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22nd International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2022

作者： Uhlmann, E. Polte, M. Bulla, B. Dambon, O. Dicke, C. Hocke, T. Thißen, K. Heper, M. Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Berlin Germany Fraunhofer Institute for Production Systems and Design Technology IPK Berlin Germany Son-x GmbH Aachen Germany

ISBN: (纸本)9781998999118

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. © European Soci

关键词： Vibration analysis

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Cooling Capacity of Oil-in-Water Emulsion under wet Machining Conditions 19

Cooling Capacity of Oil-in-Water Emulsion under wet Machinin...

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19th CIRP Conference on Modeling of Machining Operations, CMMO 2023

作者： Nabbout, Kaissar Sommerfeld, Martin Barth, Enrico Uhlmann, Eckart Bock-Marbach, Benjamin Kuhnert, Jörg Institute of Process Engineering Otto-von-Guericke-University Magdeburg Universitätsplatz 2 Magdeburg39106 Germany Technische Universität Berlin Pascalstr. 8-9 Berlin10587 Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstr. 8-9 Berlin10587 Germany Fraunhofer Institute for Industrial Mathematics ITWM Fraunhofer-Platz 1 Kaiserslautern67633 Germany

Many industrial machining operations are carried out under wet machining conditions. Modelling and simulating fluid-structure-interactions and conjugate heat transfer are still a challenge nowadays. In this paper, temperature dependent heat transfer coefficients (HTC) h(T) are experimentally estimated for wet machining-like conditions in a jet cooling experiment. The transient temperature is thereby used to solve an Inverse Heat Transfer Problem for HTC function estimation. Determined HTC are applied as input in related jet cooling simulation using the Finite-Pointset-Method (FPM) to validate the modeling approach. Additionally, wet cutting simulations numerically highlight the influence of determined HTC h(T) on turning. © 2023 Elsevier B.V.. All rights reserved.

关键词： Cooling

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Micro-texture dependent temperature distribution of CVD diamond thick film cutting tools during turning of Ti-6Al-4V 6th

Micro-texture dependent temperature distribution of CVD diam...

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6th CIRP Conference on Surface Integrity, CSI 2022

作者： Uhlmann, E. Schröter, D. Gärtner, E. Pascalstr. 8-9 Berlin10587 Germany Fraunhofer Institute For Production Systems And Design Technology Ipk Pascalstr. 8-9 Berlin10587 Germany Fraunhofer Institute For Machine Tools And Forming Technology Iwu Reichenhainer Str. 88 Chemnitz09126 Germany

Machining titanium alloys such as Ti-6Al-4V results in a high thermomechanical load on cutting tools and consequently short tool lifes. With respect to a necessary reduction of the resulting cutting tool temperatures, ultrashort pulse (USP) laser fabricated micro-textured rake faces offer direct supply of cooling lubricant into the cutting zone and lead to a reduced heat induction. As a result, micro-textured CVD diamond thick film cutting tools are also capable of machining high-performance materials due to reduced contact temperatures. In the scope of the research, the resulting temperature distribution for micro-textured rake faces will be compared under both dry and wet process conditions. Measurements show a reduction of the resulting cutting tool temperatures of ΔÏ't = 27.9 % using micro-textured cutting tools compared to non-textured cutting tools. A validated simulation provides valuable information about the contact temperatures enabling a specific development of the micro-texture geometry. As a result, a reduction of the contact temperature between chip and rake face by ΔÏ'T = 24.7 % was possible. © 2022 The Authors.

关键词： Turning

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DEM Simulation of Abrasive Brushing Processes on Additively Manufactured Workpieces

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Procedia CIRP 2025年 133卷 203-208页

作者： Anton Hoyer Eckart Uhlmann Institute for Machine Tools and Factory Management (IWF) Technische Universität Berlin Pascalstr. 8-9 10587 Berlin Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstr. 8-9 10587 Berlin Germany

Brushing with bonded abrasives is a finishing process mainly used for deburring, edge rounding, and surface roughness reduction. The brushing tools consist of flexible polymer filaments embedded with abrasive grains, allowing them to adapt to complex workpiece shapes. However, interactions between filaments lead to complex motion, chipping, and wear behaviors, making it difficult to predict work results. The discrete element method (DEM) has been shown to be effective in simulating process forces, contact areas, and filament interactions on flat workpieces. Consequently, this article focuses on processing geometrically complex workpieces, particularly additively manufactured turbine fan blades (Ni-Cr-Co), using round brushes with bonded silicon carbide. First, a vectorized iterative method is introduced to generate artificial filament patterns, enhancing DEM simulation accuracy compared to state-of-the-art filament pattern models. Subsequently, dry brushing experiments are carried out on a fan blade feature demonstrator, aiming to achieve homogeneous roughness reduction. The qualitative analysis of the contact surface suggests that results from DEM simulations can reduce the need for costly technological investigations and prototypes.

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Simulation of ultrasonic-assisted grinding for improved efficiency in hard-to-machine materials: A direct approach to analyze material removal mechanisms

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Procedia CIRP 2025年 133卷 209-214页

作者： Eckart Uhlmann Bernhard Gülzow Xinyu Zhang Technische Universität Berlin Institute for Machine Tools and Factory Management (IWF) Pascalstr. 8-9 10587 Berlin Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstr. 8-9 10587 Berlin Germany

The application of ultrasonic superposition is utilized in industrial manufacturing to enhance the chip formation mechanisms, particularly when machining hard-to-machine materials. The institute for Machine Tools and Factory Management (IWF) systematically investigates the interactions between tool and workpiece during ultrasonic-assisted grinding of high-performance ceramics. To gain an in-depth understanding of the microscopic engagement conditions, these conditions are analyzed by simulation. For this purpose, a Python simulation tool based on a geometrical-kinematic modeling approach was developed to analyze the ultrasonic-assisted circumferential longitudinal grinding process. It was demonstrated that ultrasonic assistance leads to smaller and more uniform chip thicknesses which reduce grinding forces and minimizes tool wear. Also, it promotes brittle chip formation mechanisms and improves the efficiency of the grinding process compared to conventional machining. For further investigation, the simulation model was adapted to the transverse face grinding process. In this context, not only the circumferential surface but also the face surface of the grinding tool is engaged with the workpiece. Additionally, the penetration of the workpiece is no longer tangential with the rotational movement but perpendicular to the tool movement. Analogous to the results of the analysis of the circumferential longitudinal grinding process, the influences of ultrasonic excitation on the engagement conditions, particularly the resulting chip thickness and surface topography for the adapted process kinematics were determined and are presented in this paper.

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Impact of illumination technique on the detectability of irregularities in high-resolution images of visual in-situ process monitoring in Laser Powder Bed Fusion 13

Impact of illumination technique on the detectability of irr...

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13th CIRP Conference on Photonic Technologies, LANE 2024

作者： Merz, Benjamin Schmidt, Jonathan Poka, Konstantin Mohr, Gunther Polte, Julian Hilgenberg, Kai Bundesanstalt für Materialforschung Und-prüfung Unter den Eichen 87 Berlin12205 Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Pascalstraße 8-9 Berlin10587 Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstraße 8-9 Berlin10587 Germany

The layerwise geometry build-up of additive manufacturing (AM) enables the possibility of in-situ process monitoring. The objective is the detection of irregularities during the build cycle, ensuring component quality and process stability. Focus of this work is the visual in-situ monitoring of the process of powder bed fusion with laser beam of metals (PBF-LB/M). Current state of the art visual monitoring systems for PBF-LB/M are limited by low resolution, allowing the detection of gross flaws. In this work a 65 Mpixel high-resolution monochrome camera is integrated into a commercial PBF-LB/M machine enabling a spatial resolution of approx. 17.2 μm/Pixel. The observed inhomogeneities are clustered into directly detectable irregularities, and indirectly detectable irregularities that can be inferred from the surface. In parallel, two different illumination techniques are realized in the process chamber and compared. The impact of the distinct illumination technique, direct light and dark field, on the identification of irregularities is evaluated. © 2024 The Authors.

关键词： Laser beams

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Comparing the performance of a nested to a continuous evolution strategy with covariance matrix adaption for optimization of drilling EDM 15

Comparing the performance of a nested to a continuous evolut...

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15th CIRP Conference on Intelligent Computation in Manufacturing Engineering, CIRP ICME 2021

作者： Uhlmann, E. Streckenbach, J. Polte, M. Osmanovic, M. Schick, F. Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Pascalstr. 8-9 10587 Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstr. 8-9 10587 Germany

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. © 2022 The Authors. Published by Elsevier B.V.

关键词： Optimization

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Validation of different tungsten carbide-cobalt grades as tool electrode material for sinking EDM 15

Validation of different tungsten carbide-cobalt grades as to...

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15th CIRP Conference on Intelligent Computation in Manufacturing Engineering, CIRP ICME 2021

作者： Uhlmann, Eckart Bolz, Robert Polte, Mitchel Börnstein, Julian Technische Universität Berlin Institute for Machine Tools and Factory Management IWF Pascalstrasse 8-9 Berlin10587 Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstrasse 8-9 Berlin10587 Germany

In sinking electrical discharge machining (EDM), tool electrode wear is crucial for an economical production. The tool electrode wear affects the process efficiency and determines the number of required tool electrodes for a specific machining process. Therefore, the relative tool wear, describing the relation of removed material volume between tool and workpiece electrode, needs to be minimised. The tool wear characteristics in sinking EDM depend strongly on EDM processing parameters and the applied electrode materials. Especially in micro-EDM, a significant increase of relative tool wear is representative. Because of its thermophysical properties tungsten carbide-cobalt (WC-Co) is a suitable material for the application as sinking EDM tool electrode. The economical production of WC-Co form electrodes for EDM sinking is enabled by recent advancements in precision milling of hard materials. Due to non-existent research on which composition of WC-Co is most advantageous for the application as sinking EDM tool electrode material, previous investigations have been intensified to describe correlations between material properties, EDM processing parameters and EDM processing results concerning material removal rate and relative tool wear. Therefore, various WC-Co grades with differing grain size and cobalt content were analysed in sinking EDM experimental studies. It was observed that the factor grain size showed an ambiguous effect concerning the process results. An increasing cobalt content led to a reduction of relative tool wear, which can be explained by the microstructure of the cobalt binder phase with its higher electrical conductivity. The WC-Co grades with beneficial EDM processing results have been further investigated in EDM parameter studies with differing tool electrode geometries. The experimental results concerning relative tool wear, with a minimum of 3 % for macro- and 5 % for micro-sized geometries, proved the suitability of specific WC-Co compositions

关键词： Electrodes

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Sensor integration in hybrid additive manufactured parts for real-time monitoring in turbine operations 21

Sensor integration in hybrid additive manufactured parts for...

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21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021

作者： Uhlmann, E. Polte, J. Kersting, R. Brunner-Schwer, C. Neuwald, T. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools Factory Management IWF Technische Universität Berlin Germany

ISBN: (纸本)9780995775190

Real-time monitoring of operation conditions such as tempeatures and vibrations enables efficiency enhancement for maintenance tasks. In energy industry monitoring of critical components such as turbine blades is essential for the operation safety. But the effective recording of critical process data is a challenging task due to the extreme operating conditions. With a hybrid processing approach combining two additive manufacturing technologies new classes of self-monitoring components become possible allowing data acquisition directly inside the component. Using the example of a turbine blade, the hybrid process chain is described. The turbine blade blank is produced via Laser Powder Bed Fusion (L-PBF) with channels for the integration of high temperature sensors. After integration cavities were closed by Laser Directed Energy Deposition (L-DED) followed by classical milling operations for part finishing. The data acquisition is integrated in state-of-the-art product lifecycle monitoring (PLM) software to create a digital twin. Evaluation shows that temperature could be successfully monitored at conditions of Θ = 550°C. © 2021 Proceedings of the 21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021. All rights reserved.

关键词： Turbomachine blades

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Improved surface generation of multi-material objects in computed tomography using local histograms 21

Improved surface generation of multi-material objects in com...

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21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021

作者： Uhlmann, E. Hein, C. Kayser, N. Duerre, G. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Machine Tools Factory Management IWF Technical University Berlin Germany

ISBN: (纸本)9780995775190

During the last decade industrial computed tomography (iCT) has become one of the most important metrological procedures for internal inspection, where it sees wide-spread use in injection molding and additive manufacturing. Evaluating the CT volume data of multi-material objects represents a major technical challenge. Due to artifacts caused by beam hardening, an over-segmentation of strongly absorbing materials occurs, severely limiting the accuracy of dimensional measurements. The goal of the project presented is the development of an innovative artifact-reduced multi-material segmentation. This is applied to and tested on various complex reconstructed CT data sets. Global approaches show high signal-to-noise-ratio (SNR) but are not able to compensate for local deviations. For smaller volumes the data sets become more consistent, but the SNR decreases due to the reduced data volume. Thus, a more localized approach for the volume image data has the potential to provide results of higher accuracy. With this newly presented algorithm it is now possible to perform segmentation of all materials, while eliminating over-segmentation errors as well as local noise artifacts almost completely for all tested datasets. © 2021 Proceedings of the 21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021. All rights reserved.

关键词： Injection molding

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