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The Line-less Mobile Assembly System Simultaneous Scheduling and Location Problem

Procedia CIRP 2022年 106卷 203-208页

作者： A.F. Buckhorst M.K.B. do Canto R.H. Schmitt Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology (IPT) Steinbachstrasse 17 52074 Aachen Germany

Line-less Mobile Assembly Systems (LMAS) operations management requires a global planning approach to benefit from the paradigm’s beneficial resilience and flexibility. LMAS’s unique property is the spatio-temporal assessment of assembly stations by mobile multipurpose resources. In mixed-integer programming (MIP), the simultaneous scheduling location problem (ScheLoc) combines two essential objectives desired for LMAS global planning and control: Finding optimal machine locations on the shop floor and finding optimal schedules for each of these machines subject to production and location constraints. However, recent ScheLoc formulations do not map the LMAS properties entirely and only respect either a single machine location for planar regions (P-ScheLoc) or parallel machines’ locations for discrete regions (D-ScheLoc). Therefore, this paper deduces the LMAS ScheLoc problem extending recent mixed-integer programs to customized production orders and spatio-temporal station assessment with individual capabilities by mobile robots for discrete environments. The model’s objective is to minimize the makespan respecting scheduling-specific, location-specific, and joining constraints. Since LMAS ScheLoc is computationally heavy, we propose the necessary criteria for input datasets. If they are not fulfilled, a solution’s existence for a given problem is precluded. Further, we present an upper bound estimate for the makespan C Make estimate for practical implementations. The analysis is executed based on an industrial sewage pump assembly use case. Test datasets exhibit different flexibility levels ultimately highlight LMAS ScheLoc’s benefits.

关键词： Line-less Mobile Assembly Systems Simultaneous Scheduling Location Flexibility in Assembly Mixed-Integer Linear Program

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Transition to a resilient and sustainable energy supply system: Decision support for manufacturing companies

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Procedia CIRP 2023年 120卷 589-594页

作者： Kilian Dickel Max Juraschek Christoph Herrmann Institute of Machine Tools and Production Technology Chair of Sustainable Manufacturing and Life Cycle Engineering Technische Universität Braunschweig Langer Kamp 19b 38106 Braunschweig Germany Fraunhofer Institute for Surface Engineering and Thin Films IST Bienroder Weg 54E 38108 Braunschweig Germany

Recent developments show that not only material supply chains but also energy supply systems can be hit by strong disruptive forces. This brings new challenges and highlights the importance of a resilient energy supply to the manufacturing industry. These challenges can be solved by implementation of technical solutions and a change of energy supply system designs. However, manifold options available to a company require a methodological approach to rapidly identify the potentially most suitable variants under individual circumstances for a specific factory. This paper introduces a simplified methodology for the first planning steps in the transition towards a resilient energy supply system of production sites. For this purpose, relevant resilience factors are identified and selected for energy supply systems of a factory. With a structured procedure, different technical system combinations are created and evaluated in respect to implementation effort and their potential impact on the resilience factors. Simultaneously, different disruptive scenarios are ranked based on likelihood and expected severity. The impact of these combinations on the energy load profile of the factory is evaluated and the results are presented based on the suitability of each energy supply system alternative in respect to the different disruptive scenarios. This provides information on the potentially most favorable options to the relevant stakeholders for further implementation. To demonstrate the applicability of the developed methodology, a case study on a battery cell factory is presented. The production of batteries is a fast-growing industry with a high relevance for the transition towards a sustainable economy while the battery production itself requires high amounts of electricity and heat at different temperature levels. Alternative supply scenarios besides the unidirectional consumption of fossil fuels are needed in in terms of sustainability and to increase resilience.

关键词： Resilience Resilient Factory Systems Flexible Energy Supply Renewable Energy

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Evaluation of the influence of different milling parameters and tool wear on the rim zone of a 5-axis milled large gear

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Procedia CIRP 2022年 108卷 43-48页

作者： Christoph Zachert René Greschert Daniel Schraknepper Jens Brimmers Thomas Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology (IPT) Steinbachstraße 17 52074 Aachen Germany

Machining of gears by 5-axis milling allows additional degrees of freedom in gear design compared to conventional hobbing processes. Changes in the machining technology influence the surface integrity and, thus, the service life of the machined gears. For this reason, different machining parameters were investigated regarding their effects on the surface layer and subsequently on service life. In this paper, the residual stresses and microstructures of a large gear manufactured by 5-axis milling and the service life of test gears are analyzed. With the results from this paper, the surface integrity and service life can be predicted depending on the machining parameters.

关键词： 5-axis-milling rim zone tool wear gear

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

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Procedia CIRP 2024年 124卷 585-589页

作者： Stephen Nugraha Putra Xiangmeng Meng Fan Yang Marcel Bachmann Michael Rethmeier Bundesanstalt für Materialforschung und -prüfung Unter den Eichen 87 Berlin 12205 Germany Technical University Berlin Institute for Machine Tools and Factory Management Pascalstraße 8-9 10587 Berlin Germany Fraunhofer Institute for Production Systems and Design Technology Pascalstraße 8-9 10587 Berlin 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.

关键词： Laser beam welding temperature dependent absorption weld pool keyhole dynamics numerical modelling

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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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Application of sustainability-oriented cyber physical production systems to grinding processes

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Procedia CIRP 2023年 120卷 553-558页

作者： Christopher Rogall Robar Arafat Tim Abraham Christoph Herrmann Technische Universität Braunschweig – Institute of Machine Tools and Production Technology (IWF) Chair of Sustainable Manufacturing and Life Cycle Engineering Langer Kamp 19b 38106 Braunschweig Germany Fraunhofer Institute for Surface Engineering and Thin Films (IST) Bienroder Weg 54 E 38108 Braunschweig Germany

The sustainable operation of grinding processes depends on various parameters. Not only does the grinding process have an enormous influence on the quality produced and the use of resources, but the peripheral systems have to be considered as well. When networked into a complete system, a collection of parameters, state variables, performance criteria and external factors is created. However, without the appropriate framework and the targeted definition of these values, no directly producible reference to a sustainability-oriented operation of the grinding system can be established. To detect the correlations and dependencies of the variables, Industry 4.0 approaches can be used to digitalize the manufacturing system. Cyber physical production systems (CPPS), when specifically designed for sustainable operation of the manufacturing system, contribute a positive impact in terms of e.g. energy and resource efficiency. In principle, CPPS initially carry an environmental backpack due to the sensor technology and hardware to be integrated, which is balanced out over the application period of the CPPS and finally results in a positive impact. Nevertheless, it has already been shown that CPPS can be made predictable in their efficiency increase through their systematic development. These advantages of a systematic development can greatly simplify the use of CPPS, especially in grinding. The inaccuracies and non-determinable factors of a grinding process are minimized in this paper using the CPPS and a systematic methodical approach. Similarly, the targeted use of sensor technology achieves the maximum benefit in terms of quality and sustainable operation. The use case in this paper is related to a grinding system in which sensory components are integrated and thus a sustainability-oriented measurement and control concept is built up. Through the integration, clear potentials are recognizable, which can be related not only to the parameters and the product quality but also

关键词： sustainable cyber physical production systems environmental impact in manufacturing resource efficient grinding processes

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A study on abrasive waterjet multi-stage machining of ceramics

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Procedia CIRP 2022年 108卷 770-775页

作者： M. Schüler T. Herrig T. Bergs Fraunhofer Institute for Production Technology IPT Steinbachstr. 17 Aachen 52074 Germany Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus Boulevard 30 52074 Aachen Germany

Abrasive waterjet (AWJ) milling is a promising technique for machining hard materials, but it is also complex to implement. In modern production scenarios, multi-stage machining is a matter of course to improve both performance and quality. Since AWJ milling is still developing, there is little knowledge about a corresponding process design. In this study, an innovative approach for AWJ multi-stage machining of a ceramic specimen is experimentally investigated. To produce either a high removal rate or a fine surface, different parameters of abrasive grit interacting with the workpiece surface and its potential for surface integrity are analyzed for future applications.

关键词： Waterjet machining ceramic surface integrity

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Edge computing-based virtual measuring machine for process-parallel prediction of workpiece quality in metal cutting

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Procedia CIRP 2022年 107卷 363-368页

作者： Ziqi Huang Marian Wiesch Marcel Fey Christian Brecher Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Steinbachstraße 19 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

Digital process twins enable in-line quality inspection and root cause analysis, thus sustainably optimizing the production ramp-up and quality control cycle. Current approaches reply on expensive computing units or platforms to perform material removal simulations followed by virtual metrology. This raises deployment costs and conflicts with industrial edge devices. In this paper, a novel analytical approach is proposed to build an edge computing-based digital twin of machining processes for the process-parallel prediction of workpiece tolerances by leveraging machine internal signals and contextualizing metadata sources along the digital process chain, i.e., the digital thread. This concept is validated with the results of a state-of-the-art digital process twin and conventional measurement data from a coordinate measuring machine.

关键词： digital twin digital shadow digital thread smart manufacturing sustainable resilient manufacturing smart sensing edge computing

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Assessing energy flexibility in non-energy-intensive manufacturing companies

Assessing energy flexibility in non-energy-intensive manufac...

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Sustainable Power and Energy Conference (iSPEC)

作者： Julia Schulz Magdalena Paul Stefan Roth Valerie Scharmer Lukas Bank Michael F. Zaeh Institute for machine tools and industrial management School of Engineering and Design Technical University of Munich Garching Germany IGCV Fraunhofer Institute for Casting Composite and Processing Technology Augsburg Germany

ISBN: (纸本)9781665485234

The ongoing energy transition to renewable energies heavily impacts even non-energy-intensive manufacturing companies (NEIMCs). This progress comes with fluctuations in electricity availability; and ultimately rising costs. Facing the transformation by applying demand-side energy flexibility measures, so far, has considered rather energy-intensive companies while leaving NEIMCs out of focus. Despite their number and economic importance in the European terrain, their demand-side potential is usually underestimated while it may be central to an overall successful adaptation. In this work, energy transition challenges posed to NEIMCs are funneled from several surveys with eight companies in the southern German manufacturing sector. They were evaluated to extract individual requirements for implementing energy-oriented manufacturing; from a NEIMC’s perspective. Experiences from the process industry were adapted custom-oriented to guideline potentially specific solutions for NEIMCs related to the energy transition using IT solutions. More broadly, this approach reflects opportunities and challenges in the NEIMC environment and outlines promising avenues to exploit energy flexibility.

关键词： Industries Renewable energy sources Electric potential Fluctuations Costs Europe Energy measurement

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Inverse Determination of the Johnson-Cook Material Model Parameters of Aluminum Al 6060 from Orthogonal Cutting Examinations

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Procedia CIRP 2022年 112卷 304-309页

作者： M. Hardt T. Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology (IPT) Steinbachstraße 17 52074 Aachen Germany

Modeling the material behavior under metal cutting conditions is a prerequisite for the successful simulation of the cutting process by means of Finite Element (FE) simulations. Here, the Downhill-Simplex-Algorithm is applied to the inverse determination of Johnson-Cook material model parameters for the Aluminum alloy Al 6060. For this purpose, orthogonal cutting experiment were conducted to set the experimental database for the inverse determination. Following, iterative FE-simulations were conducted in order to determine the material model parameters. The results of the inverse determination showed to result in a good agreement between simulated and experimental results within a small number of iterations.

关键词： Material Model Johnson-Cook Inverse Determination Finite Element Simulation

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