Fraunhofer-Institut für Produktionsanlagen und Konstruktionstechnik IPK

Filters
Reset filters

Settings
Now showing 1 - 10 of 1475
No Thumbnail Available
Publication

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).

View
No Thumbnail Available
Publication

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.

View
No Thumbnail Available
Publication

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 %.

View
No Thumbnail Available
Publication

Particle contact conditions for cutting edge preparation of micro-milling tools by the immersed tumbling process

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

For increasing tool life and cutting length of micro-milling tools the cutting edge preparation was successfully established. Using the immersed tumbling process, a reproducible cutting edge preparation with constant cutting edge radii as well as low chipping of the cutting edges can be realised. For a profound understanding of the preparation process and the process mechanisms further knowledge about the particle interactions with cutting tools as well as the particle flow mechanisms needs to be obtained. In this investigation the preparation process of micro-milling tools was analysed and the contact-mechanisms as well as the resulting pressures were investigated by simulation studies. Using the discrete element method (DEM) with the software ROCKY DEM from the company ESSS, Florianópolis, Brasil, the immersed tumbling process could be modelled and particle contacts, particle traces as well as particle interactions with the micro-milling tool can be visualized. Especially the particle-tool interactions were more accurately investigated by analysing the stresses and particles shear work as well as correlations between these parameters to prove the comparability between the process simulation and the real preparation process.

View
No Thumbnail Available
Publication

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.

View
No Thumbnail Available
Publication

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.

View
No Thumbnail Available
Publication

Improved surface generation of multi-material objects in computed tomography using local histograms

2021 , Uhlmann, Eckart , Hein, Christoph , Kayser, Nicolas , Dürre, Gregor

During the last decade industrial computed tomography (iCT) has become one of the most important metrological procedures for internal inspection, where it sees wide-spread use in injection molding and additive manufacturing. Evaluating the CT volume data of multi-material objects represents a major technical challenge. Due to artifacts caused by beam hardening, an over-segmentation of strongly absorbing materials occurs, severely limiting the accuracy of dimensional measurements. The goal of the project presented is the development of an innovative artifact-reduced multi-material segmentation. This is applied to and tested on various complex reconstructed CT data sets. Global approaches show high signal-to-noise-ratio (SNR) but are not able to compensate for local deviations. For smaller volumes the data sets become more consistent, but the SNR decreases due to the reduced data volume. Thus, a more localized approach for the volume image data has the potential to provid e results of higher accuracy. With this newly presented algorithm it is now possible to perform segmentation of all materials, while eliminating over-segmentation errors as well as local noise artifacts almost completely for all tested datasets.

View
No Thumbnail Available
Publication

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.

View
No Thumbnail Available
Publication

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.

View
No Thumbnail Available
Publication

Simulation and compensation of the thermal behaviour of industrial robots

2021 , Uhlmann, Eckart , Polte, Julian , Mohnke, Christian

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 tP, is the thermal heating and the associated thermal drift ÎAPt of the tool center point. The maximum deviation from the actual nominal position can reach up to ÎAPt = 1.5 mm. In the investigations, a simulation model for an industrial robot was created and the thermal behaviour was mapped. With this model, the thermal error ÎAPt within the working area can be determined as a function of the current position X and temperature Ï. These data can be used for a targeted correction of the robot path. With the correction by the compensation model the amount of drift for real milling processes could be reduced to a value of ÎAPt = 0.042 mm. The results can help to reduce the influence of thermal heating and the associated thermal drift ÎAPt of the TCP without using cost-intens ive measures with additional hardware and software on external computers for compensating the errors.

View