Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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Numerical investigation into cleanability of support structures produced by powder bed fusion technology

2022 , Campana, Giampaolo , Uhlmann, Eckart , Mele, Mattia , Raffaelli, Luca , Bergmann, André , Kochan, Jaroslaw , Polte, Julian

Purpose: Support structures used in laser powder bed fusion are often difficult to clean from unsintered powder at the end of the process. This issue can be significantly reduced through a proper design of these auxiliary structures. This paper aims to investigate preliminary the airflow within differently oriented support structures and to provide design guidelines to enhance their cleanability, especially the depowdering of them. Design/methodology/approach: This study investigates the cleanability of support structures in powder bed fusion technology. Digital models of cleaning operations were designed through computer-aided engineering systems. Simulations of the airflow running into the powder entrapped within the thin walls of auxiliary supports were implemented by computational fluid dynamics. This approach was applied to a set of randomly generated geometrical configurations to determine the air turbulence intensity depending on their design. Findings: The resul ts, which are based on the assumption that a relationship exists between turbulence and powder removal effectiveness, demonstrated that the maximum cleanability is obtainable through specific relative rotations between consecutive support structures. Furthermore, it was possible to highlight the considerable influence of the auxiliary structures next to the fluid inlet. These relevant findings establish optimal design rules for the cleanability of parts manufactured by powder bed fusion processes. Originality/value: This study presents a preliminary investigation into the cleanability of support structures in laser powder bed fusion, which has not been addressed by previous literature. The results allow for a better understanding of the fluid dynamics during cleaning operations. New guidelines to enhance the cleanability of support structures are provided based on the results of simulations.

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Characterization and application of assistance systems in digital engineering

2021 , Stark, Rainer , Brandenburg, Elisabeth , Lindow, Kai

A broad range of assistance systems can be found in manufacturing practice as well as in the corresponding literature. Similarly, it can be observed that there is a growing need for and an increasing supply of assistance systems of all kinds. However, for digital manufacturing, the assistance systems are not clearly characterized. The diversity in application areas and possible uses varies and there are no possibilities for comparison. This paper addresses the topic of assistance systems and examines the various basic elements of engineering activities in terms of possible types of assistance systems based on research in manufacturing industry. Crucial aspects of assistance capabilities for engineering are elaborated and possible digital approaches are validated based on investigations in the field of aircraft engine design and assembly.

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Resilienz durch dynamisches Prozessmanagement

2021 , Knothe, Thomas , Oertwig, Nicole , Woesthoff, Julia , Sala, Alessandro , Lütkemeyer, Marius , Gaal, Alexander

Krisen treten regelmäßig auf und betreffen aufgrund zunehmender Globalisierung immer mehr Unternehmen gleichzeitig. In diesem Beitrag wird ein Ansatz für ein dynamisches Prozessmanagement vorgestellt, welches die Fähigkeit der Früherkennung von Disruptionen und gleichzeitig auch Routine sowie Agilität im Normal- wie auch im Krisenmodus durchgängig unterstützt.

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Fatigue recognition in overhead assembly based on a soft robotic exosuit for worker assistance

2021 , Kuschan, J. , Krüger, J.

Physical stress and overuse during assembly tasks is one of the main causes of musculoskeletal disorders of workers. Innovative body-worn robotic assist systems aim to reduce the physical stress in manual assembly and handling operations. A novel approach for automatic fatigue detection using machine learning techniques, combined with body-borne sensors, enables early detection and classification of fatigue. This article introduces the new method for an innovative soft robotic exosuit for physical worker assistance. The feasibility of the method is demonstrated in a case study for overhead car assembly.

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Steigerung der Energieeffizienz mittels Energiekennzahlen am Beispiel der Metallverarbeitung

2022 , Sigg, Stefan , Kühn, Armin , Schmidt, Alexander , Roder, Sven , Thiele, Gregor , Krüger, Jörg

Die Energiewende und die einhergehende Forderung nach Effizienzsteigerungen stellen produzierende Unternehmen vor betriebliche und technische Herausforderungen. Methoden und Technologien des Energiemanagements gewinnen damit auch im Mittelstand an Relevanz. Dabei sind Kennzahlen ein Schlüssel, um die aktuelle Energieeffizienz einzuschätzen und Potenziale für Einsparungen zu identifizieren. Der Artikel dokumentiert Erfahrungen der Anwender mit Bezug auf Konzepte aus der Wissenschaft, um Interessierten aus der Industrie den Einstieg in das Thema zu erleichtern.

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MBSE-Modellierung für Verhaltens- und Struktursimulation

2021 , Zimmermann, Thomas

echnische Systeme werden mithilfe von Modellbasiertem Systems Engineering (MBSE) beschrieben, um eine domänenübergreifende Wissensbasis zu erzeugen, die es den beteiligten Stakeholdern ermöglicht, Systemelemente konsistent und parallel zu entwickeln. Die Qualität dieser Modelle ist maßgeblich dafür, wie effizient dieses Wissen aus dem MBSE auch zur Systemexploration verwendet werden kann, um Systemzusammenhänge zu analysieren, indem verschiedene Modellarten gemeinsam simuliert werden.

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Steuerung von Laser-induzierten periodischen Oberflächenstrukturen

2021 , Uhlmann, Eckart , Souza Schweitzer, Luiz Guilherme De , Schneider, Peter , Michel, Andre , Hein, Christoph

Laser-induzierte periodische Oberflächenstrukturen (LIPSS) weisen ein hohes Potenzial für Anwendungen in den Bereichen der Oberflächenfunktionalisierung auf. Die Steuerung der Richtung dieser Nanostrukturen kann nur durch Änderung der Laserpolarisation erfolgen. Auf dem Markt gibt es kein System zur automatischen Änderung der LIPSS-Orientierung. Für den industriellen Einsatz ist dies vom Vorteil, um Inhomogenität im Strukturverlauf zu vermeiden. In diesem Beitrag wird eine Systemlösung vorgestellt, indem die Steuerung der Richtung von Nanotexturen ermöglicht wird.

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High-stiffness Control of Series Elastic Actuators using a Noise Reduction Disturbance Observer

2022 , Asignacion, A. , Haninger, K. , Oh, S. , Lee, H.

Rendering a high impedance on a series-elastic actuator (SEA) can improve motion control performance while retaining collision safety by a lower physical stiffness. The safe impedance range can be increased with high gain velocity feedback control, but in practice this is limited by noise. This paper applies the noise reduction disturbance observer (NRDOB) to inner-loop velocity control of an SEA, attenuating noise and allowing higher safe rendered stiffness compared with standard torque and torque/velocity hierarchical control. Closed-form expressions for maximum passive stiffness and Z-region are found, shown to depend strongly on the high-frequency noise gain, and used to optimize the control gains. Performance is experimentally verified on a reaction-force SEA; validating the passivity of the high stiffness control in impact (free space and stiff environment) while rendering a safe stiffness 3.0 times the intrinsic stiffness.

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Analysis of influencing factors for the dressing process in double side face grinding

2021 , Uhlmann, Eckart , Lichtschlag, Linus

In grinding, the design of the dressing process is an essential part of work preparation and restoration of the grinding wheel's profile and cutting ability. In contrast to most grinding processes, the choice of dressing parameters in double face grinding with planetary kinematics has so far only been experience-based. As a consequence, the dressing process causes a higher degree of tool wear than the machining of the workpieces. A focused design of the dressing process based on a scientific data could help to improve the ecological and the economic efficiency by reducing tool wear and the amount of dressing tools used. In this paper, methods for determining the wear condition and the result of the dressing process, including macro- and microscopic characteristic are presented. This includes a correlation analysis between parameters of wear characteristics and workpiece surface quality. Furthermore, technological investigations are carried out in order to systematically limit the main influencing factors on the dressing process. As a result, the parameters dresser grain size dgd, rotational speed ratio nld and the machined dresser height ∆hd are identified as significant for dressing. The knowledge about their principal influence on the dressing result could provide the basis for further research.

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Hyperconnected Ecosystems für industrielle Netzwerke

2021 , Jäkel, Frank-Walter , Gering, Patrick , Knothe, Thomas

Das Hyperconnected Ecosystems für industrielle Netzwerke wird definiert als die Vernetzung aller relevanten Informationen und deren Erreichbarkeit jederzeit und von überall (hyperconnected). Barrieren zwischen Netzwerkpartnern bzgl. Datenbereitstellung und Zugriff werden reduziert und an aktuelle Anforderungen ausgerichtet. Die Evolution des Netzwerkes wird durch dessen dynamische Anpassbarkeit und flexible Einbindung von Diensten ermöglicht. Schlussendlich soll jede erforderliche Information an jedem Ort sofort in einer bearbeitbaren Form und möglichst ohne Aufwand verfügbar sein. Die Metapher des sozialen Netzwerks, in denen sich Partner finden und nach Bedarf Daten und Leistungen austauschen, dient als Basis für die Strukturen im Netzwerk. Dabei müssen industrielle Anforderungen nach Sicherheit, Souveränität und Transparenz integriert werden. Der Beitrag beschreibt die Vision eines Hyperconnected Ecosystem für industrielle Netzwerke und erste Ansätze zu dessen Umsetzung.

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