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Manufacturing of carbide tools by Selective Laser Melting

Procedia Manufacturing 2018年 21卷 765-773页

作者： Eckart Uhlmann André Bergmann Robert Bolz Fraunhofer Institute for Production Systems and Design Technology (IPK) Pascalstraße 8-9 Berlin 10587 Germany Technische Universität Berlin – Institute for Machine Tools and Factory Management (IWF) Pascalstraße 8-9 Berlin 10587 Germany

Application fields of electrical discharge machining (EDM) are limited due to given process conditions. When producing structures of high aspect ratios or using multi-axis machining, removed particles assemble at the machining zone, leading to process instabilities and increasing tool wear. A promising approach to improve EDM process conditions is the utilization of flushing channels in the tool electrode. However, with increasing complexity of the electrode geometry and the local integration of the mentioned flushing channels, conventional electrode manufacturing reaches its limitations. By applying Selective Laser Melting (SLM), these limitations are eliminated. An additional benefit is the efficient use of material during SLM, where nearly no waste is produced, because remaining powder can be used for the next SLM-process. The appropriate integration of flushing channels, even for complicated electrode geometries, improves process conditions during EDM in a variety of applications, leading to a higher material removal rate V W and reduced tool wear ϑ compared to machining without flushing. Additionally, the number of required tool electrodes can be reduced, as SLM enables an efficient integration and miniaturization of all features in a single electrode, what results in a far more sustainable process chain. Of particular interest in the field of EDM is carbide. Because of its wear resistance and stability, it is an ideal electrode material, which is commonly applied in µEDM. Tungsten carbide-cobalt is representative for this group of materials, which is already used in tool manufacturing. Several tests show a general suitability of carbide tool electrodes made by SLM for EDM-processing. However, the SLM process parameters and the composition of the carbide-cobalt show significant impact to the EDM results. A lower proportion of cobalt leads to reduced material removal rates, whereas the level of tool wear remains at a similar level. In order to benefit from the a

关键词： additive manufacturing selective laser melting electrical discharge machining tungsten carbide

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Concept of Sustainable Data for a Selective Laser Melting Machine

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Procedia Manufacturing 2018年 21卷 655-662页

作者： Eckart Uhlmann Rodrigo Pastl Pontes Abdelhakim Laghmouchi André Bergmann Fraunhofer Institute for Production Systems and Design Technology (IPK) Pascalstraße 8-9 Berlin 10587 Germany Technische Universität Berlin – Institute for Machine Tools and Factory Management (IWF) Pascalstraße 8-9 Berlin 10587 Germany

Due to increased digitalization in the production environment, data, information, and sustainable management approaches should be developed in order to enable production machines for data acquisition, data exchange and data analysis. Especially for additive manufacturing technologies, those approaches are extremely important to detect and avoid failures in the manufacturing process. A critical failure during the manufacturing process could lead to a defective workpiece, wasting resources. Within this context, this work addresses the concept of sustainable data for a selective laser melting machine tool. The selective laser melting process is one of the additive manufacturing technologies that is capable of producing lighter and more complex functional workpieces in comparison to conventional manufacturing technologies. Beyond the use of the machine tool system internal data (e.g. process data, internal sensors), additional information such as energy consumption and data provided using external sensors are required to detect the current condition of production process. In order to observe if the considered data sources are capable of identifying abnormal conditions of the machine tool, failures from five subsystems were inserted during a manufacturing process of a reference workpiece. Four of the five data sources detect failures that influenced the layer quality while they are occurring. Thus, the results could be used to allow the operator to take measures to save energy and resources.

关键词： Production SLM machine data management information analysis

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Wear behaviour of diamond coated micro-milling tools during micro machining 17

Wear behaviour of diamond coated micro-milling tools during ...

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17th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017

作者： Uhlmann, E. Kuche, Y. Oberschmidt, D. Polte, J. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Germany

ISBN: (纸本)9780995775107

Graphite electrodes are used in the die sinking process for manufacturing of micro structured tools in the die and mould fabrication. They are machined using the micro-milling process. During the cutting process graphite grains have strong abrasive effects on the cutting edges and lead to high tool wear. Consequences are short path length lc and geometrical errors. One approach to reduce tool wear is the tool coating with diamond. The diamond coating changes the cutting edge micro geometry which has influences on the process behaviour. In this paper, the wear behaviour of micro-milling tools with diameter D = 0.5 mm and different micro geometries is analysed and discussed. The results show better wear behaviour for prepared and coated tools.

关键词： Coatings

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Modeling approach regarding surface functionalization by force-controlled micro and nano forming 17

Modeling approach regarding surface functionalization by for...

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17th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017

作者： Uhlmann, E. Kühne, S. Jagodzinski, M. Malcher, M. Trevino, R. Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Germany Fraunhofer Institute for Production Systems and Design Technology IPK Germany

ISBN: (纸本)9780995775107

Surface functionalization allows the control of fluidic, tribological, biological or optical properties. Suitable processes are interference lithography (IL), ultra-precision machining and micro and nano forming. The force-controlled forming process enables a reproducible production of structures with an absolute height in the double-digit nanometer range. The deformation is a complex process consisting of controlled and uncontrolled material deposition. Knowledge about the uncontrolled behaviour, however, allows a reproducible production of defined structures. A model approach with regard to machining parameter prediction is presented here. The tool shape is transferred into the surface by plastic penetration of a faceted diamond tool. By means of a superimposed tool movement, linear structures can be generated. Larger areas can be structured by repeating this process. The advantage of the force control in comparison to the displacement control is a defined penetration depth relative to the surface with reproducibility in the single-digit nanometer range. The force-control is carried out gravimetrically (0.05 N -1-1, 30 nm 2neg2) is considered as ideal load. As additional result of these experiments, physical approaches are available, which can later form the basis of a physical model.

关键词： Optical properties

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Measurement of in-mould shear rates by x-ray particle image velocimetry 17

Measurement of in-mould shear rates by x-ray particle image ...

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17th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017

作者： Uhlmann, E. Hein, C. Oberschmidt, D. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Germany

ISBN: (纸本)9780995775107

The manufacturing of large quantities of polymeric optical and micro-optical components becomes more and more important regarding industrial applications as MEMS devices, customer electronics or micro imaging systems. The relevant parameters for the qualification of polymeric micro optics as surface roughness, shape and positional tolerances, refractive index, molecular orientation, injection moulding process induced deviations and their connection to injection moulding parameters are largely known. The manufacturing of micro optics by micro injection moulding and associated with that, micro injection moulding machine tools with highly complex plastification and injection systems is far less understood. In particular, the influence of shear loads and temperature deviation on replication quality has not been fully investigated. The occurring shear rates during injection moulding lead to mechanical damage of the polymer on a molecular level and reduced optical functionality. This work presents an approach for in mould shear rate measurement by the use of a metrological computed tomography system. Using metal powder with a particle size 3 μm ≤ dp ≤ 5 μm as tracer particles, Polyetheretherketon (PEEK) as mould material, a Zeiss Metrotom 800 computer tomography system and a Babyplast injection unit, streamlines of polymer flow could be visualized. In accordance to optical particle image velocimetry (PIV), for each frame a matrix including particle position was calculated. The temporal shift of these positions lead to velocity gradients that allow the calculation of shear-rates. By reproducing relevant elements of injection units and mould structures, this works enables the profound investigation of fluid dynamics regarding micro injection moulding and the correlation between shear loads and polymer characteristics.

关键词： Injection molding

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Distributed Motion Planning for Industrial Random Bin Picking

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Procedia CIRP 2018年 76卷 121-126页

作者： Vojtěch Vonásek Axel Vick Jörg Krüger Czech Technical University in Prague Faculty of Electrical Engineering Technicka 2 166 27 Prague Czech Republic Fraunhofer Institute for Production Systems and Design Technology (IPK) Berlin Germany Department of Industrial Automation Technology Technische Universität Berlin Germany

The task of bin picking is to automatically unload objects from a container using a robotic manipulator. A widely used solution is to organize the objects into a predictable pattern, e.g., a workpiece carrier, in order to simplify all integral subtasks like object recognition, motion planning and grasping. In such a case, motion planning can even be solved offline as it is ensured that the objects are always at the same positions. However, there is a growing demand for non-structured bin picking, where the objects can be placed randomly in the bins. This arises from recent trends of transforming classical factories into smart production facilities allowing small lot sizes at the efficiency of mass production. Due to unknown positions of the objects in the non-structured bin picking scenario, trajectories for the manipulator cannot be precomputed, but they have to be computed online. Sampling-based motion planning methods like Rapidly Exploring Random Tree (RRT) can be used to plan the trajectories. In this paper, we propose a modification of RRT for distributed motion planning aiming to reduce the runtime. The planning task is first simplified by computing several guiding waypoints. The waypoints are distributed to a set of planners running in parallel and each planner computes a short trajectory between two given waypoints. Connecting the waypoints is easier than solving the original task, therefore each planner runs fast. In comparison to other parallel motion planning techniques, the proposed approach does not require any communication among the computational nodes, which is more suitable for cloud-based computing. The proposed work has been verified both in simulation and on a prototype of a bin picking system.

关键词： Industrial Robot Path Planning Cloud Robotics Distributed Control Sampling-based motion planning

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Cutting forces while machining STAVAX ESU with binderless-cBN 17

Cutting forces while machining STAVAX ESU with binderless-cB...

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17th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017

作者： Uhlmann, E. Oberschmidt, D. Polte, J. Polte, M. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Germany

ISBN: (纸本)9780995775107

Binderless-cubic-Boron-Nitride(cBN) from the company SUMITOMO CORPORATION, Itami, Japan, provides the opportunity for direct cutting of steel with ultra-precision quality without additional equipment or coating of the workpiece. This work presents the latest results in the field of ultra-precision machining of hardened stainless steel with binderless-cBN. In this paper the influence of the cutting speed vc, the feed f, the depth of cut ap, and the cooling lubricant on the cutting force Fc is shown for turning the stainless steel STAVAX ESU. The cutting speed, the feed and the depth of cut were varied between 3 m/min ≤ vc ≤ 450 m/min, 0.9 μm ≤ f ≤ 9.7 μm, and 5 μm ≤ ap ≤ 30 μm respectively. As cooling lubricants compressed air and W200SL of the company OPORTET, Duisburg, Germany, with a volumetric flow rate = 1 l/min were used. For measuring the cutting forces Fc the piezoelectric dynamometer MINIDYN 9256C2 from the KISTLER INSTRUMENTE AG, Middlefield, USA, was used. As a result of this work cutting forces Fc ≤ 4.9 N could be observed with an inconstant progression over the varied process parameters.

关键词： Compressed air

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Manufacturing of CVD diamond micro-end mills with electrical discharge machining 17

Manufacturing of CVD diamond micro-end mills with electrical...

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17th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017

作者： Uhlmann, E. Oberschmidt, D. Polte, M. Polte, J. Schimmelpfennig, T.-M. Börnstein, J. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Germany

ISBN: (纸本)9780995775107

At state of the art micro-milling tools made of cemented carbide are widely used in industry. Nevertheless, these micro-milling tools suffer from fast and random tool breakage while cutting. To improve the wear behaviour of micro-milling tools new cutting materials have to be established. In this work electrical discharge machining (EDM) for manufacturing of micro-milling tools with cutting edges made of boron doped chemical vapour deposition (bdCVD) diamond were investigated. Wire-EDM and die-sinking-EDM were compared regarding the characteristics of the micro-tool's cutting edges. It could be concluded that the wire-EDM process is suitable for manufacturing of micro-milling tools with cutting edges made of bdCVD diamond. With respect to the elaborated technologies for the wire-EDM process a cutting edge radius rβ = 3.9 μm and for the die-sinking-EDM process a cutting edge radius rβ = 5.4 μm could be measured.

关键词： Milling (machining)

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Liquid covered micro-milling 17

Liquid covered micro-milling

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17th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017

作者： Uhlmann, E. Oberschmidt, D. Polte, M. Polte, J. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Germany

ISBN: (纸本)9780995775107

Micro-milling tools made of cemented carbide suffer from fast tool wear and random tool breakage during the machining process. The cutting material cemented carbide is composed of a hard material phase made of tungsten carbide and a binder phase made of cobalt. An allotropical crystal lattice transformation of the binder phase at a temperature υ = 420 °C leads to increased tool wear. Commonly minimum quantity lubrication (MQL) is used as cooling lubricant technology in micro-milling. In this work a new liquid covered cooling lubricant (LCCL) technology and the commonly used MQL technology were compared regarding tool wear of cemented carbide tools for machining the steel STAVAX ESU. In the LCCL technology the cutting process is completely covered with cutting lubricant. It could be concluded that the new LCCL technology offers a high potential to reduce the tool wear in micro-milling of steel with cemented carbide micro-milling tools.

关键词： Wear of materials

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Dry-EDM milling of micro-scale features with high speed rotating tungsten tube electrodes 17

Dry-EDM milling of micro-scale features with high speed rota...

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17th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2017

作者： Uhlmann, E. Perfilov, I. Schimmelpfennig, T.-M. Schweitzer, L. Yabroudi, S. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Germany

ISBN: (纸本)9780995775107

Micro electrical discharge milling is an alternative to die-sinking EDM for the machining of three-dimensional micro-structures or cavities with free-form surfaces. An important advantage provided by micro-EDM milling for this purpose is the possibility to use simple pin or tube electrodes with diameters de ≤ 500 μm. This reduces the manufacturing costs of the workpiece and decreases the setup time for positioning electrodes. The high density of conventional dielectric fluids and the resulting small working gap cause a severe contamination of the working gap with particles and as a consequence short-circuits and process instability. The use of gaseous dielectrics, like compressed air, leads to enhancements in the flushing conditions and the cooling of the tool and workpiece electrodes. The gas is injected through the tube electrode under high pressure, resulting in high flow velocities and a removal of melted material from the working gap. A new spindle with a maximum rotation speed of n ≤ 400,000 rpm was developed by the institute for Machine Tools and Factory Management IWF of the Technische Universität Berlin for the realization of micro dry-EDM milling with tube electrodes. The high speed rotation of the tool electrode stabilizes the process and increases the material removal rate due to better flushing conditions. This paper presents the equipment and machining results of dry-EDM milling of simple micro-scale features.

关键词： Electrodes

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