Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

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PowerGrasp: Development Aspects for Arm Support Systems

2022 , Goppold, J.-P. , Kuschan, J. , Schmidt, H. , Krüger, J.

Exoskeletons can support workers on physically demanding tasks, but in industry they lack of acceptance. This contribution gives an insight into design aspects for upper body exoskeletons, especially how active exoskeletons for industrial applications differ from military and medical use-cases. To overcome typical rigid exoskeleton problems, we suggest the use of modular soft-exosuit support systems and therefore checked different types of soft actuation principles for their eligibility for the use on upper body joints. Most promising approach is using two-layered actuators sting of robust fabric with embedded rubber tubes as pressure chambers. By inflating the tubes, it is possible to vary the stiffness of the chambers, which can be effectively used to generate assisting forces and moments at human joints (shoulder, elbow, wrist, finger).

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How Pedestrians Perceive Autonomous Buses: Evaluating Visual Signals

2021 , Brandenburg, Elisabeth , Kozachek, Diana , Konkol, Kathrin , Woelfel, Christiane , Geiger, Andreas , Stark, Rainer

With the deployment of autonomous buses, sophisticated technological systems are entering our daily lives and their signals are becoming a crucial factor in human-machine interaction. The successful implementation of visual signals requires a well-researched human-centred design as a key component for the new transportation system. The autonomous vehicle we investigated in this study uses a variety of these: Icons, LED panels and text. We conducted a user study with 45 participants in a virtual reality environment in which four recurring communication scenarios between an autonomous driving bus and its potential passengers had to be correctly interpreted. For our four scenarios, efficiency and comprehension of each visual signal combination was measured to evaluate performance on different types of visual information. The results show that new visualization concepts such as LED panels lead to highly variable efficiency and comprehension, while text or icons were well ac cepted. In summary, the authors of this paper present the most efficient combinations of visual signals for four reality scenarios.

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Towards a Framework for Impact Assessment of Research & Technology Organisations

2021 , Kidschun, Florian , Hecklau, Fabian

Due to their ability to bridge the gap between knowledge created by basic research and market requirements, Research and Technology Organisations (RTOs) play a major role in countriesâ innovation systems. Their R&D results should lead to innovations, which in turn generate the economic output of public investment in research and development. Moreover, they should support the foundation of new companies and industrial innovations. RTOs can thus be seen as intermediaries between R&D and the industry, while they themselves constitute to a certain extent entrepreneurs and actors in applied R&D that focus on industrial and commercial application right from the start of their activities. Therewith, RTOs pursue to increase the competitiveness of the entire economy. With a growing demand for evaluating their actual contribution in national innovation systems, simply stating the goal of positive impact to stakeholders like governments, the public, investors etc. is not enough; its accomplishment needs to be proven by robust evidence. In this regard, the value of an impact assessment is determined by the strength of the evidence produced and the credibility of the evaluation. RTOâs research activities and their impacts are diverse in nature and occur across many sectors of the economy. To gain transparent insights into relevant and comprehensive performance metrics showing the impact of RTOs from a micro- and macroeconomic perspective, impacts are only appropriate for evaluation if a causal relationship can be drawn back to their origin. While some impacts are primarily economic and suitable for quantitative analysis, others have to be evaluated qualitatively. Regardless of its type, each impact needs to be assessed within a common framework to enable a comprehensive understanding of RTO's impact. Within this contribution, an impact assessment framework is established with the aim to enable the identification of causal relationships between impacts and their origin.

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Additive manufacturing of precision cemented carbide parts

2021 , Polte, Julian , Polte, Mitchel , Lahoda, Christian , Hocke, Toni , Uhlmann, Eckart

Cemented carbide parts are commonly used as wear resistance components in a broad range of industry, e.g. for forming, mould making and matrices. At state of the art the machining of precision cemented carbide components by milling is strongly limited due to excessive tool wear and long machining times. Promising approaches for precision machining of cemented carbide components are dedicated cutting tool coatings, new cutting materials like binderless polycrystalline diamond and ultrasonic-assisted machining. Nevertheless, for all these approaches the components need to be machined of monolithic materials. The new approach addresses an innovative manufacturing process chain composed of near net shape Additive Manufacturing followed by a precision finishing process. Within this investigations for the manufacturing of precision cemented carbide parts, cemented carbide with a cobalt content of 17 % and a grain size in a range of 23 µm ⤠gs ⤠40 µm were used. As Addit ive Manufacturing technology laser powder bed fusion was used. Diamond slide burnishing and immersed tumbling were investigated as finishing technologies. Based on the investigations, a dedicated process chain for the manufacturing of precision cemented carbide parts could be realised. The findings show that the developed process chain composed of near net shape Additive Manufacturing and the finishing process diamond slide burnishing enables the manufacturing of precision cemented carbide parts with a geometrical accuracy of ag ⤠10 µm. Due to the finishing process the initial surface roughness after Additive Manufacturing could reduce by Ra = 89 %.

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Time-Sensitive Networking over Metropolitan Area Networks for Remote Industrial Control

2021 , Tschöke, Simon , Lynker, Frederic , Buhr, Hauke , Schreiner, Florian , Willner, Alexander , Vick, Axel , Chemnitz, Moritz

The benefits of the currently evolving IEEE Time-Sensitive Networking (TSN) standard have already been globally recognized. Whereas the application of TSN in a LAN is currently widely and globally tested, TSN in a Metropolitan Area Network (MAN) has not been a major focus until now. The possible benefits of utilizing co-located Edge Clouds in order to support multiple urban production sites with industrial realtime applications open a wide range of new business models. Therefore, we have analyzed the feasibility of transparently using PROFINET over TSN via a Dense Wavelength Division Multiplex (DWDM) link, where a machine park is controlled remotely by an Edge-based virtual Programmable Logic Controller (vPLC). As a result, we are able to setup a TSN connection over a MAN with a one-way delay of about 156.5 J.ms and a jitter of about 12 ns. This work can be extended to allow for dynamically provisioned TSN flows and multi-path Frame Replication and Elimination (FRER) for distributed hard real-time machine control and adoption to Ultra-Reliable Low-Latency Communication (URLLC) 5G campus networks.

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Investigation of the gap bridgeability at high-power laser hybrid welding of plasma-cut thick mild steels with AC magnetic support

2021 , Üstündag, Ö. , Bakir, N. , Gumenyuk, A. , Rethmeier, M.

One of the challenges of the high-power hybrid laser welding of thick steels is the sensitivity of the process of the process to manufacturing tolerances. This usually leads to a time-consuming preparation of the welding edges, such as milling. The study deals with the influence of the edge quality of milled and plasma-cut steel made of S355J2 with a wall thickness of 20 mm on the laser hybrid welded seam quality. Furthermore, the gap bridgeability and the tolerances towards edge misalignment was investigated. An AC magnet was used as backing support to prevent sagging and positioned under the workpiece, to generate an upwards directed electromagnetic pressure. The profiles of the edges and the gap on the top and root side were measured using a digital camera. Single-pass laser hybrid welds of plasma-cut edges could be welded using a laser beam power of just 13.7 kW. A gap bridgeability up to 2 mm and misalignment of edges up to 2 mm could be achieved successful. Additionally, the independence of the cutting side and the welding side was shown, so that samples were welded to the opposite side to their cutting. For evaluation of internal defects or irregularities, X-ray images were carried out. Charpy impact strength tests were performed to determine the toughness of the welds.

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Production environment of tomorrow (ProMo)

2021 , Kuschan, Jan , Müller, Vinzenz , Monchinger, Stephan , Heimann, Oliver , Niebuhr, Carsten , Kabha, Oday

Small defects in the grain or major damage to a moulded part or tool can bring production to a standstill. SMEs in particular have neither the personnel nor the equipment to repair such damage on their own, so they send it to specialised contractors. The repair process is carried out manually, depending on the accuracy requirements, and is usually completed by a finishing process. This work requires qualified personnel and, at the same time, requires a lot of time in case of larger damages. In this paper we present a way to map the Maintenance, Repair and Operations (MRO) process chain in a partially automated manner. The symbiosis of individual technologies results in a significantly increased efficiency of the MRO process chain, which continues to focus on people and their process knowledge. While Directed Energy Deposition (DED) for the MRO of moulded parts is used widely, usually a high manual effort in measuring the component geometries and teaching of the machine tool paths is necessary. However, there are clear advantages compared to the manufacture of new parts or manual laser welding repair. At the same time, the resource and energy requirements can often be significantly reduced compared to new part production. ProMo focuses on automating the time-consuming machine programming by reducing the number of necessary work steps in CAD/CAM-based program creation. Based on a subsequent robot-guided scan, a digital actual 3D model is generated. Due to intelligent path planning algorithms, no manual programming of the robot is necessary and at the same time it is possible to detect components of different sizes, shapes and covers in this system with a minimum of effort. In addition, the operator passes on elementary information, such as the approach path of the milling head, to the subsequent processes by means of finger gestures and can thus significantly reduce tedious CAM programming steps. Now, the scanned component is transferred to a 3D-CAD model and a target/actual comparison is created for the damaged areas. Those are milled out in a defined manner and then restored using DED.

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Simulating flow behaviour of wet particles within the immersed tumbling process

2021 , Uhlmann, Eckart , Polte, Julian , Kuche, Yves , Landua, Fabian

For many production chains, it is mandatory to involve special finishing of the manufactured parts for the chipping of the edges as well as the polishing of surfaces. One commonly used method is the immersed tumbling process, where any workpiece is dragged through a particle filled container. In many cases, the immersed tumbling process operates in environments with added liquids, leading to changes in particle-tool interaction and general flow behaviour of the used particles. Whilst the discrete element method for simulating particles is mainly limited to dry particles, the used software ROCKY DEM from ESSS, Florianópolis, Brasil, comes with a built-in liquid-bridge model to simulate water-covered particles and granulate and furthermore an extension for system couplings with Ansys Fluent of the company ANSYS, INC., Canonsburg, Pennsylvania. The latter can be used to create from both software one three-phase-model with higher amounts of actually simulated water. In thi s study, small amounts of water were added to differently shaped particles using the build-in liquid-bridge model, to analyse and compare the particles flow characteristics in both, wet and dry environments. To gather significant information leading towards precise comparisons, the particles trajectories, velocities and resulting forces against the workpieces can be specifically observed and analysed, whilst this kind of process knowledge could previously never been taken into account without simulation.

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

2021 , Uhlmann, Eckart , Streckenbach, Jan , Thißen, Kai , Schulte Westhoff, Bela , Masoud, Abd Elkarim , Maas, Jürgen

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 compa red to the original geometry.

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Reduction of erosion duration for electrical discharge drilling using a nature analogue algorithm with nested strategy types

2021 , Uhlmann, Eckart , Polte, Mitchel , Streckenbach, Jan , Osmanovic, Mirsad

The required high economic efficiency, combined with the corresponding high quality demands, in the aerospace industry as well as in mould and tool making, motivate the necessity of finding suitable parameter combinations for the process of electrical discharge machining (EDM), e.g. when introducing new materials. To counteract this, various methods are being investigated in research for the optimisation of EDM. One new method is the stochastic optimisation procedure evolution strategy (ES). Due to its metaheuristic approach, this optimisation method is excellently suited for very complex processes in which the interrelationship of the individual influencing variables is not known. This publication presents the results of the investigation of the suitability of the ES optimisation method using the example of electrical discharge drilling. For this purpose, two nested ES-types were investigated. The electrode materials used were brass for the tool and stainless steel X5C rNi18-1 for the workpiece. As a result, the erosion duration could be reduced by 30 %. This investigation forms the basis for the use of nested ES types in electrical discharge drilling.

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