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An Improved Model for Contour Damage Compensation in 3D Waterjet Machining

Procedia CIRP 2021年 102卷 387-392页

作者： M. Dadgar T. Schreiner M. Schüler T. Herrig T. Bergs Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany AIXPath GmbH Henricistrasse 50 52072 Aachen Germany Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen university Campus-Boulevard 30 52074 Aachen Germany

Waterjet machining is a particularly flexible and powerful tool for processing of high-performance materials which are difficult to machine conventionally. Waterjet cutting is a non-conventional and time efficient cutting technique without any significant thermal influence. However, it is difficult to handle as contour damages such as striations and taper angle arise in the component for 3D cutting applications. Consequently, it is mainly used in industry just for simple cutting tasks. Therefore, the main goal of this study is to compensate the contour damages of 3D cutting applications by employing an optimized model for 3D waterjet cutting. By using the optimized model with a particular dynamic process control, the necessary required inputs of the currently prevailing 3D waterjet processing are decreased. Moreover, these processes have been optimized in terms of reducing the striation and taper angle formation. By overcoming the contour damages during 3D waterjet cutting, the utilization potential of the waterjet machining for modern productions has been increased.

关键词： Waterjet machining 3D cutting Contour damage Striation Taper

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With synthetic data towards part recognition generalized beyond the training instances

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AIP Conference Proceedings 2024年第1期2989卷

作者： Paul Koch Marian Schlüter Jörg Krüger Fraunhofer Institute for Production and System Design Technology Pascalstraße 8-9 10587 Berlin Germany Technical University Berlin Institute for Machine Tools and Factory Management Pascalstraße 8-9 10587 Berlin Germany

In this work we investigate the effect of using synthetic data, generated in a simulation, in order to pre-train an AI-based image classification for industrial components. After pre-training we use real camera-captured training images to fine-tune the AI with the aim to close the Sim2Real domain gap. We compare our approach to purely using real training images of a single candidate object instance. In an exemplary case study for screw recognition, we found that a given AI classification algorithm dropped its recognition rate from 99.8% to 88.5% when testing the algorithm with known and unknown screw instances of the learned object classes, respectively. Employing our pre-training method on the basis of synthetic data, the drop in recognition rate is decreased from 99% to 96.95%. Thus, our proposed method has only a relative drop of 2.05% when shifting towards a generalized domain (including unknown part instances), while a compared approach on the basis of real camera-captured data showed a drop of 11.3%.

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Screening-based evidence of the impact of geometrical deviations on inner stresses on mechanical presses

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Procedia Manufacturing 2019年 27卷 185-191页

作者： N. Wagner T. Päßler Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Straße 88 09126 Chemnitz Germany

In recent years various cases of damage analysis have shown an increasing number of overload scenarios resulting in failures of entire press structures. This happens in spite of manufacture-compliant utilization and a correct press design process based on state-of-the-art methods such as FEM simulation. This paper proves the hypothesis that geometrical tolerances, defined clearances and geometrical signs of wear have a significant impact on residual stress of a press, by conducting an empirical sensitivity analysis. The focus is on mechanical presses with four-point leverage actuation as an example for highly over-determined press structures. As proven by FEM simulation, the identified geometrical deviations result in a preload of the press structure, amounting up to 10% of its theoretical sustainable stress. The significant impact of geometrical deviations on the residual stress has been proven successfully for the empirically determined assumption.

关键词： Press Tolerancing Residual stress

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Monitoring concept for structural integration of PZT-fiber arrays in metal sheets:a numerical and experimental study

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International Journal of Smart and Nano Materials 2018年第1期9卷 56-67,I0003页

作者： Welf-Guntram Drossel Andreas Schubert Matthias Putz Hans-Joachim Koriath Volker Wittstock Sebastian Hensel Alexander Pierer Benedikt Müller Marek Schmidt Fraunhofer Institute for Machine Tools and Forming Technology ChemnitzGermany Professorship for Adaptronics and Lightweight Design Chemnitz University of TechnologyChemnitzGermany Professorship Micromanufacturing Technology Chemnitz University of TechnologyChemnitzGermany Professorship for Machine Tools and Forming Technology Chemnitz University of TechnologyChemnitzGermany

The technique joining by forming allows the structural integration of piezoceramic fibers into locally microstructured metal sheets without any elastic interlayers.A high-volume production of the joining partners causes in statistical deviations from the nominal dimensions.A numerical simulation on geometric process sensitivity shows that the deviations have a high significant influence on the resulting fiber stresses after the joining by forming operation and demonstrate the necessity of a monitoring *** this basis,the electromechanical behavior of piezoceramic array transducers is investigated experimentally before,during and after the joining *** piezoceramic array transducer consists of an arrangement of five electrical interconnected piezoceramic *** findings show that the impedance spectrum depends on the fiber stresses and can be used for in-process monitoring during the joining *** on the impedance values the preload state of the interconnected piezoceramic fibers can be specifically controlled and a fiber overload.

关键词： Impedance spectroscopy joining by forming process monitoring function integration sensitivity

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On the validity of the Reynolds equation for the simulation of wet grinding processes

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PAMM 2023年第3期23卷

作者： Paul Thunich Oliver Schömig Yan Tong Robar Arafat Christoph Herrmann Michael Müller Institute of Dynamics and Vibrations TU Braunschweig Braunschweig Germany Institute of Machine Tools and Production Technology TU Braunschweig Braunschweig Germany Fraunhofer Institute of Surface Engineering and Thin Films (IST) Braunschweig Germany

Wet grinding is a process with a complex interaction of individual sub-processes such as fluid mechanics, continuum mechanics and thermodynamics and branched coupling of corresponding properties. In order to be able to represent these properties in a model, this paper develops a description of the hydrodynamic properties in the grinding gap as a building block for a simple but accurate model to describe the process of wet grinding. To this end, it is shown that the Reynolds equation, which is well-established in the lubrication theory, is also suitable for describing an exemplary grinding wheel with abrasive grains or pores. This is done by demonstrating the feasibility of a calculation and by comparing the results with Computational Fluid Dynamics (CFD) simulations.

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Load and energy management for factories through multi-stage production planning and optimization

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Procedia CIRP 2019年 80卷 257-262页

作者： Marian Süße Bastian Prell Johannes Stoldt Hanns-Martin Strehle Mark Richter Andreas Schlegel Matthias Putz Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Straße 88 09126 Chemnitz Germany

The production phase has a major influence on the embodied energy of many products and, thus, their overall environmental performance. As a result, manufacturing enterprises are prompted to raise their energy efficiency and flexibility to improve their products’ sustainability. The simultaneous integration of renewable energy sources and decentral storages is a feasible option in this but also require consistent solutions for appropriately planning and controlling the operation of the entire factory system. This paper proposes an iterative multi-stage heuristic optimization for intelligent load and energy management. A load profile of the production plan, based on the minimized overall makespan, is checked against the available energy supply to identify demands and opportunities to shift single jobs based on calculated buffer times. Whenever infeasibility is determined, the process returns to the previous production planning stage for further alterations. This cycle is initiated regularly (e.g. weekly) or following certain events (e.g. long-lasting machine failure) and terminates once all restrictions are observed or if a termination threshold (e.g. calculation time) is reached. The experimental setup used for developing and validating this approach to energy-aware factory operation makes use of a probabilistic material flow simulation model. It provides information on tasks to be scheduled and executes production plans to evaluate the performance of the proposed solution. This new approach to energy-aware factory operation also provides opportunity to integrate additional ecologic criteria to improve the sustainability of manufactured products.

关键词： Energy efficiency Production planning Optimization Simulation

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Predictive quality for hypoid gear in drive assembly

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Procedia CIRP 2021年 104卷 702-707页

作者： Jimmy Chhor Stefan Gerdhenrichs Robert H. Schmitt Laboratory for Machine Tools and Production Engineering WZL of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany BMW Group Laaberstraße 7 84130 Dingolfing Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

In rear axle drive assembly, drive bevel gear and crown gear are aligned within a narrow tolerance range and installed in the gearbox. Due to limited adaptability after installation, the ideal dimension is estimated a priori based on physical correlations and empirical correction terms. This paper follows a data-driven approach to predict the installation dimension with sufficient accuracy within a comprehensive optimization strategy in industrial application. An initial evaluation with production data logged in day-to-day operations suggests a significant improvement in accuracy compared to status quo and contributes to the dissemination of predictive analytics in industrial practice.

关键词： Predictive analytics predictive quality data-driven optimization rear axle drive hypoid gear

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Profile cross rolling for the local hardness increase in helical components such as extruder screws

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Procedia Manufacturing 2019年 27卷 39-44页

作者： E. Forke D. Landgrebe Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Straße 88 09126 Chemnitz Germany

Highly developed production technologies facilitate unique component characteristics depending on the respective manufacturing objective. However, often several technologies are required in a sequential manner to achieve either the geometrical or the mechanical component properties. Innovative stainless steel alloys show an outstanding work hardening capability. Therefore, they are of great interest for the development of an enhanced burnishing process. The incremental cold forming technology of profile cross rolling can be applied to burnish machined preforms. This paper examines an approach for the geometrical preform design. Starting from the geometrical surface of revolution, the procedure is further developed to helical component surfaces. Both numerical and experimental results indicate that the preform design allows attaining a hardness increase in highly loaded component subsurface regions. This hardness increase goes along with low geometrical deviations and high surface integrity. Hence the results allow the conclusion that this technological development enables the achievement of several component characteristics with one fast burnishing operation. This might lead to an increased acceptance of forming technologies in industries that are usually characterized by pure machining processes. Such an industry could be plastics compounding.

关键词： rolling hardening extrusion

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A computer vision system for saw blade condition monitoring

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Procedia CIRP 2021年 104卷 1107-1112页

作者： Nicolas Jourdan Tobias Biegel Volker Knauthe Max von Buelow Stefan Guthe Joachim Metternich Institute of Production Management Technology and Machine Tools (PTW) Otto-Berndt-Str. 2 6428 Darmstadt Germany Interactive Graphics Systems Group (GRIS) Fraunhoferstr. 5 64283 Darmstadt Germany Fraunhofer-Institute for Computer Graphics Research (IGD) Fraunhoferstr. 5 64283 Darmstadt Germany

Tool condition monitoring is a key component of predictive maintenance in smart manufacturing. Predicting excessive tool wear in machining processes becomes increasingly difficult if different materials need to be processed. We propose a novel computer vision-based system for saw blade condition monitoring that is independent of the processed materials and combines deep learning with classic computer vision. Our approach allows for accurate condition monitoring of blade wear which can further be used for predictive maintenance. Additionally, the system can classify different defect types such as missing blade teeth, thus preventing the production of scrap parts.

关键词： Condition monitoring computer vision deep learning saw blade wear

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Production planning for optimal mass pre-distribution for axial feed cross rolling

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Procedia Manufacturing 2019年 27卷 192-196页

作者： N. Schubert J. Steger M. Gerlach B. Lorenz Fraunhofer Institute for Machine Tools and Forming Technology IWU Reichenhainer Strasse 88 09126 Chemnitz Germany

At present, the process selection, the selection of tools and tool materials are key functions for the economic efficiency of manufacturing lines. The continuous improvements in production technology, including the related machine and tooling technology, have made it possible to increase both economic efficiency and resource efficiency in production. As a result of the market demand for a high variety of products and the constant change in the demand structure, the requested volume of individual product types is reduced – the trend towards small-series production is constantly increasing. In hot bulk forming processes, it is usually not possible to produce the workpiece in just one forming step. As an alternative to the well-known machining processes for optimized preforms, the axial feed cross rolling process was developed from wedge cross rolling. Due to the all-purpose tools, the use of this process is already economical for very small batch sizes. In order to achieve optimum results with regard to optimized mass pre-distribution, the process parameters during rolling must be kept within close limits. If this is the case, axial feed cross rolling allows additional material savings of between 12% and 15% compared to other preforming processes. In order to achieve best results, the preform operation is designed by using FE simulation axial feed cross rolling.

关键词： Hot deformation Production planning Finite element method (FEM)

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