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

作者： Uhlmann, E. Sturm, H. Polte, M. Hocke, T. Polte, C. Polte, J. Institute for Machine Tools and Factory Management IWF Technische Universität Berlin Pascalstr. 8-9 Berlin10587 Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstr. 8-9 Berlin10587 Germany Unter den Eichen 87 Berlin12205 Germany

ISBN: (纸本)9781998999118

Cemented carbide is used in a wide range of industrial applications as a wear-resistant material, e.g. in mould making and forming industry. At state of the art, the machining of cemented carbide is severely limited because of the hardness, high strength and the resulting wear resistance of the material. Due to the brittle-hard character cemented carbide materials suffer from surface cracks during the machining. The brittle-hard character and the related phenomena result in high tool wear. A promising approach for the machining of cemented carbide is the use of the novel cutting material binderless nanopolycrystalline diamond (NPD) with a dedicated cutting edge design. Within this work, laser machined tools with a corner radius of r?= 400 µm are fully characterized, investigated by Raman spectroscopy regarding the condition of the diamond and applied for first cutting experiments. Cutting investigations were carried out using specimens with a tungsten carbide content of cC = 88 %, a cobalt content of cCo= 12 % and a grain size of dg= 0.5 µm. Prior to these investigations, the condition of the diamonds and possible changes due to the lasered cutting edges were examined by Raman spectroscopy. During the cutting investigations, the brittle-ductile transition as well as the minimum chip thickness were identified by scratching tests. It could be shown that a hydrostatic stress state can be used to achieve ductile chip formation using cemented carbide as workpiece material. © European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022. All rights reserved.

关键词： Tungsten carbide

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Numerical study on the temperature characteristic of material absorptivity and its significance in high-power laser beam welding 13

Numerical study on the temperature characteristic of materia...

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13th CIRP Conference on Photonic Technologies, LANE 2024

作者： Putra, Stephen Nugraha Meng, Xiangmeng Yang, Fan Bachmann, Marcel Rethmeier, Michael Bundesanstalt for Materialforschung und -Pröfung Unter den Eichen 87 Berlin12205 Germany Technical University Berlin Institute for Machine Tools and Factory Management Pascalstraße 8-9 Berlin10587 Germany Fraunhofer Institute for Production Systems and Design Technology Pascalstraße 8-9 Berlin10587 Germany

The absorptivity of metallic materials plays an important role in high-power laser beam welding. It affects the amount of absorbed laser power leading to the heating and melting of the surfaces to be joined and is highly dependent on the temperature. Nonetheless, this key characteristic is often ignored in numerical simulations and an empirical parameter determined by trial-And-error approaches is rather implemented to calibrate the results. In the present work, the temperature dependence of laser absorption is included in a three-dimensional multiphase numerical model considering the coupled fluid flow and heat transfer. The calculated laser absorption is determined by the temperature-dependent material properties, laser characteristics, and incident angle of the laser beam. It is found that the temperature dependence of the laser absorption is crucial for accurately determining the keyhole and weld pool geometries, which is validated by experimental measurements using 304 austenitic steel. © 2024 The Authors.

关键词： Laser beam welding

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Green incremental learning - Energy efficient ramp-up for AI-enhanced part recognition in reverse logistics

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Procedia CIRP 2023年 116卷 414-419页

作者： Marian Schlüter Robert Schimanek Paul Koch Clemens Briese Vivek Chavan Pinar Bilge Franz Dietrich Jörg Krüger Fraunhofer Institute for Production and Design Technology (IPK) Pascalstr. 8-9 Berlin 10587 Germany Technical University Berlin Institute for Machine Tools and Factory Management Pascalstraße 8-9 10587 Berlin Germany

Artificial Intelligence (AI) has made significant progress in supporting circular economy and reverse logistics by learning from diverse data to predict, e.g., routes or to assist workers in sorting. However, it remains an open question how AI can be integrated and trained into such operational processes, where little to no data has been collected previously. Traditionally, AI models would only be rated by their accuracy. This paper aims to introduce the concept of green incremental learning, i.e. rating AI models not only for their accuracy but to evaluate energy efficiency as well. A ramp-up of a data-driven AI system for part recognition is explored under consideration of energy efficiency. Therefore, we combine online and incremental learning, working with growing data sets to simulate a ramp-up phase. We present experiments of incremental learning on business and image data, partially supported by regular joint training steps. We start local CPU-based machine learning and prediction on business data from the first sample. Finally, we compare incremental learning to traditional batch learning and show energy-saving potential of up to 62 % without a significant drop in accuracy.

关键词： Circular economy reverse logistics incremental learning computer vision machine learning

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Concept for an actuated variable tool electrode for use in sinking EDM 21

Concept for an actuated variable tool electrode for use in s...

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

作者： Uhlmann, E. Streckenbach, J. Thißen, K. Schulte Westhoff, B. Masoud, A. Maas, J. Fraunhofer Institute for Production Systems and Design Technology IPK Germany Institute for Machine Tools Factory Management IWF Technische Universität Berlin Germany Mechatronic Systems Lab. Technische Universität Berlin Germany

ISBN: (纸本)9780995775190

Typically, a large number of individual tool electrodes has to be used in sinking electrical discharge machining (sinking EDM) to successfully machine a single workpiece. Due to non-uniform wear and insufficient flushing of the working gap electrode geometries have a significant effect on the process efficiency. This paper discusses the use of an actuated variable tool electrode for sinking EDM to reduce the number of required tool electrodes and to increase the overall process efficiency. A miniaturised linear actuator was developed to individually move electrode segments to form the target shape for the tool electrode. The coordinated actuation of bundled electrode segments introduces new methods for the active flushing within the working gap, which cannot be implemented in conventional sinking EDM. Intelligent sinking strategies can further improve process efficiency by creating and sinking sub-geometries into the workpiece offering improved flushing conditions compared to the original geometry. © 2021 Proceedings of the 21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021. All rights reserved.

关键词： Electrodes

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Towards High-Payload Admittance Control for Manual Guidance with Environmental Contact

arXiv

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arXiv 2022年

作者： Haninger, Kevin Radke, Marcel Vick, Axel Krüger, Jörg The Department of Automation The Fraunhofer Institute for Production Systems and Design Technology Germany

Force control enables hands-on teaching and physical collaboration, with the potential to improve ergonomics and flexibility of automation. Established methods for the design of compliance, impedance control, and collision response can achieve free-space stability and acceptable peak contact force on lightweight, lower payload robots. Scaling collaboration to higher payloads can allow new applications, but introduces challenges due to the more significant payload dynamics and the use of higher-payload industrial robots. To achieve high-payload manual guidance with contact, this paper proposes and validates new mechatronic design methods: standard admittance control is extended with damping feedback, compliant structures are integrated to the environment, and a contact response method which allows continuous admittance control is proposed. These methods are compared with respect to free-space stability, contact stability, and peak contact force. The resulting methods are then applied to realize two contact-rich tasks on a 16 kg payload (peg in hole and slot assembly) and free-space co-manipulation of a 50 kg payload. © 2022, CC BY.

关键词： Industrial robots

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Constructive compensation of the thermal behaviour for industrial robots 13

Constructive compensation of the thermal behaviour for indus...

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13th International DAAAM Baltic Conference and 29th International Baltic Conference, BALTMATTRIB 2021

作者： Uhlmann, Eckart Polte, Julian Mohnke, Christian Fraunhofer Institute for Production Systems Design Technology IPK Pascalstraße 8-9 Berlin10587 Germany Institute of Machine Tools and Factory Management Pascalstraße 8-9 Berlin10587 Germany

Industrial robot systems offer a flexible, adaptable basis due to their kinematics and their mobility 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 ΔAPt = 1.5 mm. Currently, there are no procedures and methods established in practice which compensate the effects of thermal drift without expensive calibration measures and system downtime. In these investigations a system was developed which allows the reduction of thermally induced displacement by using controlled heating elements. The aim is to keep the entire robot system at a permanent, balanced temperature level. The heating elements are adapted to the geometry of the respective axis and heat the material to a temperature ϑ close to the steady state. A comparison of the drift through the heating system with the error occurring in normal operation shows that the drift of the heating system is comparable with the drift of normal heating. With the heating mats, a thermally induced error of ΔAPt = 0.234 mm can be generated within t = 20 min. While normal heating requires up to t = 600 min. The achieved error deviation of the drift of the self-heating to the heated variants is with ΔAP = 0.04 mm only minimal. The results can help to reduce the influence of thermal heating and the associated thermal drift of the TCP without using cost-intensive measures with additional hardware and software on external computers for compensating the errors. © 2021 DAAAM International. All rights reserved.

关键词： Industrial robots

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Biological transformation: Principles to enhance holistic production systems

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Procedia CIRP 2022年 110卷 293-298页

作者： Annika Lange Thomas Knothe Holger Kohl Günther Seliger Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstraße 8-9 10587 Berlin Germany Technische Universität Berlin Pascalstraße 8-9 10587 Berlin Germany

In today’s production systems, the digital transformation is fully in progress. But the next evolution step can be seen on the horizon, biological transformation. This means the application of biomimetics principles with the aim of low-effort, resource-saving, reversible and adapted economies. Because of their aim regarding minimization of resource consumption and stability orientation even in turbulent environments, biomimetics principles can contribute to the major challenges of production systems, climate change, environmental protection, as well as the turbulences as generated by globalization and individualization in this paper it is described how biological transformation can contribute to extend and improve holistic production systems. For this purpose, traditional principles of holistic production systems are reflected with the ones coming from digitization and biomimetics.

关键词： Holistic production systems biological transformation characteristics transformation

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Holistic Concept towards a Reference Architecture Model for Predictive Maintenance 54

Holistic Concept towards a Reference Architecture Model for ...

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54th CIRP Conference on Manufacturing Ssystems, CMS 2021

作者： Uhlmann, Eckart Polte, Julian Koutrakis, Nikolaos-Stefanos Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstraße 8-9 Berlin10587 Germany Technische Universität Berlin Pascalstraße 8-9 Berlin10587 Germany

In the era of digital transformation of factories, one of the most challenging applications of the Industrial Internet of Things (IIoT) is predictive maintenance. This paper presents a holistic concept for predictive maintenance together with a reference architecture that includes data acquisition on the sensor level, edge computing and digital twin applications. For that purpose, condition-based maintenance, lifecycle monitoring and digital assistance systems are integrated to develop application-specific digital twins based on the proposed architecture, integrating heterogenous data sources in order to enhance the accuracy of the machine learning models. The concept is illustrated through an experimental use case. © 2021 The Author(s).

关键词： Data acquisition

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Novel Advances in Machine Tools, Tool Electrodes and Processes for High-Performance and High-Precision EDM 15

Novel Advances in Machine Tools, Tool Electrodes and Process...

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

作者： Uhlmann, Eckart Polte, Mitchel Yabroudi, Sami Technische Universität Berlin Institute for Machine Tools and Factory Management Pascalstrasse 8-9 Berlin10587 Germany Fraunhofer Institute for Production Systems and Design Technology Pascalstrasse 8-9 Berlin10587 Germany

High-performance electrical discharge machining (EDM) is a key technology for manufacturing high-precision components in a broad range of industrially relevant applications. Formation of debris in the working gap leads to arcing and short-circuits on the surface as well as related inaccuracies and process instabilities. Despite decades of research in the field of EDM excessive tool wear and limited process performance are still challenging. In order to overcome highly complex state-of-the-art challenges, dedicated processes, machine tools, peripheral systems, software, tool electrodes and technologies for the application of alternative dielectric fluids have been developed. Within this work novel advances in the development of a sophisticated dry EDM machine tool, including generator and process control technology based on open architecture, open source software, and commonly available machine tool components, are presented. Solutions for challenges regarding remaining debris and gas bubbles as well as related arc discharge and short-circuit pulses in sinking EDM are presented by new flushing methods, technologies and devices. A new system for inverted pressure flushing of a dielectric fluid in ED-drilling enables a highly efficient removal of debris and gas bubbles through the interior channels of the tool electrode. A new multi-luidic spindle system for EDM provides the ability to use performance- and material-related application of gaseous, near-dry and liquid dielectric fluids sequentially within a single machining process. Recent advances in tool electrode design, tool electrode material application, modification and production have led to essential process improvements. A helical tool electrode design significantly improved flushing conditions and related material removal rate in ED-drilling. Modification of ED-drilling tool electrode surfaces by thermal oxidation of copper reveals a promising approach to minimize ineffective discharges. Application of a speci

关键词： Debris

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Two-colour thermography for measurement of temperature distribution in laser beam welding

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Procedia CIRP 2024年 124卷 468-471页

作者： A. Gumenyuk N. Bakir M. Rethmeier Bundesanstalt für Materialforschung und -prüfung (BAM) Unter den Eichen 87 12205 Berlin Germany Technische Universität Berlin Pascalstrasse 8-9 10587 Berlin Germany Fraunhofer Institute for Production Systems and Design Technology IPK Pascalstrasse 8-9 10587 Berlin Germany

Solidification cracking is a frequently observed phenomenon in laser beam welding of austenitic stainless steels and other metallic alloys. Characterisation of cracking susceptibility requires knowledge of the precise and spatially resolved temperature distribution near the solidification front in the welding process. Thermography is a standard tool that provides a qualitative estimate of the 2D temperature field. The general disadvantage of this method is its dependence on the emission characteristics of the measured object. For welding applications, these can vary significantly in the temperature range above and below the melting temperature. For this purpose, we have developed a thermography-based measurement technique using a SWIR camera system in combination with two narrow bandpass filters that use the principle of two-wavelength pyrometry to estimate absolute temperature values. This technique was used to determine the temperature distributions and gradients near the solidification front of laser-welded austenitic steel. The results were validated by other measurements.

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