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Constructive methods to reduce thermal influences on the accuracy of industrial robots

Procedia Manufacturing 2019年 33卷 19-26页

作者： Christian Mohnke Sascha Reinkober Eckart Uhlmann Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstraße 8-9 10587 Berlin Germany Institute of Machine Tools and Factory Management Pascalstraße 8-9 10587 Berlin Germany

Due to their kinematics and their mobility, industrial robot systems offer a flexible, adaptable basis. An influencing variable, which is particularly relevant for processes with long process times, is the thermal heating and the associated thermal drift of the tool center point. The maximum deviation from the actual nominal position can reach up to 1.5 mm. To counteract these displacements, a cooling strategy or a targeted preheating can be installed. Both possibilities were evaluated under constructive, energetic and economic aspects and implemented on at least one axis of an industrial robot. Furthermore, a structural thermal decoupling and optimized design of the respective components were carried out. The results can help to reduce the influence of thermal heating and the associated thermal drift of the TCP by structural support without using cost-intensive measures with additional hardware and software on external computers for compensating the errors.

关键词： Robot Thermal Error Machining

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Ductile machining of brittle materials for manufacturing micro-optic components 18

Ductile machining of brittle materials for manufacturing mic...

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18th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2018

作者： Uhlmann, E. Oberschmidt, D. Rolon, D.A. Kühne, S. Jagodzinski, M. Malcher, M. 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)9780995775121

Due to the geometry and specification of micro-optic components, these may not be ground or polished, therefore they demand other manufacturing processes such as ultra-precision (UP) machining with defined cutting edge tools. Despite previous studies, the machining of brittle materials remains a challenge for manufacturing those components in UP processes. For example, ductile machining of silicon is extensively studied, however, ductile machining of materials such as Zerodur®, GaP, U.L.E.® and glass is still a challenge to overcome. Therefore, this paper aims at reporting the ductile or part-ductile machining of silicon and Zerodur® pieces in UP processes. Experiments were carried out using UP-shaping and plane turning processes in an UP-machine tool. Moreover, monocrystalline diamond tools were employed. During UP-turning experiments, the process forces were measured. The machining results were obtained by White Light Interferometer (WLI) of the representative machined surfaces. In order to complement the experiments, simulations were performed in finite element software to comprehend the influences of the rake angle on ductile machining of those materials. After the UP-shaping experiments, the depth of cut was determined for each of the mentioned materials together with the main influence of each process parameter. Furthermore, a reduction of parameter ranges for UPturning experiments was accomplished. Using design of Experiments for UP-turning tests, the main influences of process parameters were observed and detailed, together with tool geometry optimization and recommendation for further experiments. The local optimum of process parameters was found as well as the accomplishment of ductile removal during the machining tests. These results and simulation models are going to be further used for a more detailed process description, as analogous tests and optimization of UP processes such as micro-milling. © 2018 CURRAN-CONFERENCE. All rights reserved.

关键词： design of experiments

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Boron-doped CVD diamond micro-end mills for machining titanium 18

Boron-doped CVD diamond micro-end mills for machining titani...

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18th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2018

作者： Uhlmann, E. Polte, M. Polte, J. 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)9780995775121

In industry micro-milling tools made of cemented carbide are widely used. However, these micro-milling tools suffer from fast and random tool breakage during the machining of hard to machine materials. Therefore, in preliminary work micro-milling tools with cutting edges made of boron doped chemical vapour deposition (bdCVD) diamond were developed. In this work new micro-milling tools were successfully applied for machining titanium grade 2. Comprehensive cutting tests were carried out to analyse the influence of the spindle speed n, the feed per tooth ft, and the depth of cut ap on the surface roughness. Further experiments addressed the wear behaviour of the developed micro-milling tools. After a path length lc of 10 m a maximum width of flank wear land VBmax of 29 μm were observed. © 2018 CURRAN-CONFERENCE. All rights reserved.

关键词： Milling (machining)

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Helical electrodes for improved flushing conditions in drilling EDM of MAR-M247 18

Helical electrodes for improved flushing conditions in drill...

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18th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2018

作者： Uhlmann, E. Yabroudi, S. Perfilov, I. Schweitzer, L. 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)9780995775121

The machining of precision holes in difficult to machine materials or alloys with high aspect ratios φ and under consideration of the cost-effectiveness of the overall process is still a challenge. Electro-discharge machining (EDM) is predestined for such purposes. Flushing is one key factor for the precise machining of bore holes with high aspect ratios φ. Nevertheless, the capabilities of the flushing conditions are often underrated regarding an improved process stability, an increased material removal rate VW, a decreased machining time tero, as well as the tool wear ΔIE. Therefore, the present investigation considers the influence of an outer geometry of cylindrical rod tool electrodes to improve the electro-discharge drilling process. Different electrodes made of brass, with helical flutes along the shank, are compared with the basic geometry, a cylindrical rod electrode, with respect to their flushing capabilities. All electrodes have an outside diameter d = 3 mm. It is suggested that the machining process will stabilise and the material removal rate VW will increase due to improved removal efficiency of erosion particles (debris). Through holes with a total depth h = 16 mm have been machined by use of design of Experiments (DoE) approved process parameters in nickel based superalloy MAR-M247. By use of a helical shaped electrode the machining time tero was reduced by 39 % compared to the cylindrical rod electrode. © 2018 CURRAN-CONFERENCE. All rights reserved.

关键词： Electrodes

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Electro-discharge drilling with MP-based carbon fibre electrodes 18

Electro-discharge drilling with MP-based carbon fibre electr...

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18th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2018

作者： Uhlmann, E. Perfilov, I. Yabroudi, S. Schweitzer, L. 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)9780995775121

For the electro-discharge drilling of micro-holes with small diameters D the production and the guidance of the tool electrode are most challenging. For holes with diameters D ≤ 50 μm the required electrodes have to be produced by electro-discharge dressing, which leads to a considerable increase in the production effort as well as the production costs. The small diameters 5 μm ≤ d ≤ 15 μm as well as the good electrical conductivity κ of carbon fibres make it possible to use a single carbon fibre as an electrode for electro-discharge drilling. The paper presents the results of experiments with non-rotating single carbon fibres as tool electrodes for electro-discharge drilling. The process parameters were optimised for the machining of through-holes in a workpiece made of stainless steel 1.4310 with a thickness h = 20 μm and h = 50 μm respectively. © 2018 CURRAN-CONFERENCE. All rights reserved.

关键词： Carbon fibers

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Diamond burnishing for mould and die industry 18

Diamond burnishing for mould and die industry

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18th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2018

作者： Uhlmann, E. Oberschmidt, D. Guhde, S. 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)9780995775121

关键词： Surface roughness

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Wear behaviour of HIPIMS coated micro-milling tools with cutting edge preparation for machining steel moulds 18

Wear behaviour of HIPIMS coated micro-milling tools with cut...

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18th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2018

作者： Uhlmann, E. Kuche, Y. 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)9780995775121

Micro-milling is an appropriate process for the industrial production of precision parts in the mould and die industry. Decisive for a long tool life is the wear resistance, which can be improved by cutting edge preparation technologies and tool coatings. Especially the improvement of the coating technology with the high power impulse magnetron sputtering (HIPIMS) provides improved tool wear behaviour and longer path length lc. Further studies compare two different HIPIMS-coatings of micro-milling tools for machining the mould steel X13NiMnCuAl4-2-1-1. Furthermore, the tool wear could be reduced due to cutting edge preparation using immersed tumbling process. In consequence of the increased cutting edge radii rβ the measured active forces Fa increased slightly. Best results were achieved for micro-milling tools with cutting edge preparation and AlTiN coating. © 2018 CURRAN-CONFERENCE. All rights reserved.

关键词： Coatings

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Pocket milling of composite fibre-reinforced polymer using industrial robot

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Procedia CIRP 2019年 85卷 183-188页

作者： Ever Grisol de Melo Tiago Borsoi Klein Sascha Reinkober Jefferson de Oliveira Gomes Eckart Uhlmann Department of Mechanical Engineering Aeronautics Institute of Technology (ITA) Marechal Eduardo Gomes 50 São José dos Campos 12228-900 Brazil Fraunhofer Institute for Production Systems and Design Technology (IPK) Pascalstraße 8-9 Berlin 10587 Germany

In the recent decades, aerospace and automotive industry are replacing metal materials by carbon fibre-reinforced polymer (CFRP). The mechanical properties of CFRP materials are very attractive due to high mechanical strength and low weight. However, there are technological challenges in the machining process for this type of material. The anisotropy and inhomogeneity of the CFRP cause high wear of the cutting tool, spalling, delamination, fuzzing, fibre pull-out, matrix cracking, thermal degradation and resulting in poor quality of the part. In addition, the requirement for processes that are more flexible within a larger work area makes the use of industrial robot (IR) a promising alternative. The present work evaluated the performance of the IR regarding motion accuracy, which influences machining conditions of composites. The trimming in a pocket milling was carried out using the factional replication of the 3k factorial design, with three levels and three factors. The tool geometry, feed rate fz and spindle speed n were selected as input parameters. In order to evaluate the robotic machining performance, resultant cutting force Fr, surface and dimensional quality were selected as output parameters to be assessed. After obtaining the force results, equations were generated for each cutting tools and Response Surface Methodology (RSM) was applied. The results show that the use of IR is a promising alternative for the CFRP machining of large aeronautical components.

关键词： carbon-fibre-reinforced polymer (CFRP) industrial robot (IR) machining process high speed cutting (HSC)

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Smart Maintenance – dynamic model-based instructions for service operations

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Procedia CIRP 2019年 81卷 1417-1422页

作者： Eckart Uhlmann David Franke Eckhard Hohwieler Fraunhofer-Institute for Production Systems an 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 the increased complexity of machines and plants service technicians have to be more trained to be able to maintain them. In many service operations it is still common to use simple service manuals like checklists. With the strong growth of the information and communication technology it is possible to create interactive and context-sensitive tools to support service technicians during operations. One problem is that these tasks are always in change by new knowledge. To solve this issue a model-based engine is being developed to dynamically generate instruction-tools for service operations for direct machine communication.

关键词： service assistance system human-machine-interaction maintenance model-based

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Manufacturing and replication of sub-10 μm micro-bowls for biomedical sensor systems 18

Manufacturing and replication of sub-10 μm micro-bowls for ...

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18th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2018

作者： Uhlmann, E. Hein, C. Polte, M. Polte, J. Dähne, L. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Germany Surflay Nanotec GmbH Germany

ISBN: (纸本)9780995775121

The technical implementation of a novel biosensor for the highly parallelized screening of biochemical binding reactions depends on the manufacturing of an array of micro-bowls with a diameter dB ≤ 10 μm with an aspect ratio ar ≥ 1. Since the operating principle of the biosensor is based on the stimulation of stationary optical waves in micro-spheres, micro-bowls for the immobilisation of these spheres in a microfluidic environment are necessary. Due to this operating principle, the micro-bowls need to separate the spheres from the fluid flow and ensure the careful adherence of single spheres, coincidently. Moreover, the pathway for the optical accessibility of the micro spheres should be unrestricted. This work presents a process chain for the manufacturing of microfluidic chips with an array of n ≥ 1,000 micro-spheres by ultra-precision milling of mold inserts, the replication by precision injection molding as well as experimental trial results. With regard to manufacturing of the mold inserts, the uniform and burr free ultraprecision milling of large aspect ratio micro posts was investigated within a parametric study. Furthermore, the replication of the micro-bowls was examined by taking the consistent replication of the entire bowl array, the adverse formation of fillets, and the replication of surfaces with optical functions into special account. By the analysis of the microfluidic and optical properties of the replicated structures, the correlation between mold manufacturing, replication, and operating conditions can be performed. © 2018 CURRAN-CONFERENCE. All rights reserved.

关键词： Biosensor Injection molding Micro-bowl Ultraprecision milling

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