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An analysis of biomechanical requirements and actuating technologies of biomimetic hand exoskeletons regarding to driving force and stroke

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Procedia CIRP 2024年 125卷 24-29页

作者： Alina Carabello Kenny Pagel Welf-Guntram Drossel Professorship Adaptronics and Lightweight Design University of Technology Chemnitz Fraunhofer Institute for Machine Tools and Forming Technology IWU

Exoskeletons have gained importance recently. In the case of musculoskeletal diseases, they can restore or support the mobility of injured body parts; in everyday life, they can relieve the musculoskeletal system and thus contributes to the preservation of health into old age. However, active systems face challenges due to the efficient and reliable actuators. In the following, the example of the hand will be used to investigate what influence the individuality of the hand under consideration has on the selection of a suitable actuator about force and stroke. The literature outlines that tendon-driven mechanism with a biomimetic design are a promising approach for hand exoskeletons: The finger is actively moved by an actuator using artificial tendons positioned along the finger to match anatomical structures. For this purpose, actuators based on electromagnetic or pneumatic principles, and smart materials are described. The requirements for force and stroke of the drive can be derived from the analysis of finger kinematics. In this study the finger kinematics of 13 subjects were analyzed. The results show a scatter in stroke and force depending on the finger considered. To select a suitable actuator for the biomimetic hand exoskeleton, these results are compared with the force and stroke characteristics of various actuating principles. The comparison reveals that the choice of the actuator depends on the intended primary support for the hand (movement, endurance, grip strength). Hence, it can be deduced that step drivers meet the force and stroke requirements and may be a suitable alternative.

关键词： exoskeleton tendon-driven step driver actuator hand injury finger movement

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Antibacterial Surface Protection using Electrical Discharge Machining with Zinc Tool Electrode for Medical Devices 6

Antibacterial Surface Protection using Electrical Discharge ...

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6th CIRP Conference on BioManufacturing, BioM 2024

作者： Bui, Viet D. Martin, André Berger, Thomas Steinert, Philipp Schubert, Andreas Chemnitz University of Technology Professorship Micromanufacturing Technology Reichenhainer Str. 70 Chemnitz09126 Germany Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Str. 88 Chemnitz09126 Germany

Electrical discharge machining (EDM), widely used to fabricate medical devices, is applicable for antibacterial surface protection. Silver, transferred from tool electrode or powder suspended in the dielectric to the modified layer during the EDM process, significantly enhanced antibacterial properties of the modified surface. However, bacterial resistance to silver, which was widespread in clinical, still posed challenges for the modified surfaces containing silver. Zinc, owing to its strong antibacterial effects and no challenge related to Zn-resistant bacteria hitherto reported in clinical, was therefore used as tool electrode material to modify Ti6Al4V surfaces during the EDM process. Discharge energies up to 170 ìJ with different polarities were applied in the EDM milling process using deionized water-based dielectric fluid. Results show that discharge energy and polarity play a vital role in chemical composition and roughness of the modified surfaces as well as material removal rate and tool wear rate. The surfaces containing zinc contents up to 28 % can be generated. The use of a low energy generates zinc-rich surfaces with less micro-cracks. The EDM process using zinc tool electrode shows a promising potential for antibacterial surface modification of medical devices. © 2024 The Authors.

关键词： Deionized water

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Investigation of Surface Characteristics in Magnetic Field assisted Electrical Discharge Machining 7

Investigation of Surface Characteristics in Magnetic Field a...

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7th CIRP Conference on Surface Integrity, CSI 2024

作者： Bui, Viet D. Martin, André Berger, Thomas Schubert, Andreas Chemnitz University of Technology Professorship Micromanufacturing Technology Reichenhainer Str. 70 Chemnitz09126 Germany Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Str. 88 Chemnitz09126 Germany

Electrical discharge machining (EDM) has demonstrated its promising potential for surface modification. The integration of materials from tool electrode or powder that is mixed into the dielectric fluid has proven to modify the workpiece surface to enhance its mechanical properties, realize antibacterial effects, or increase biocompatibility. Recent EDM studies showed that due to non-contact forces, properties of the modified surface such as roughness values and the thickness of modified layer were significantly influenced when using magnetic field assisted EDM. Consequently, in this study, an external magnetic field with a strength of 0.66 T is used to assist the material transfer from tool electrode to workpiece surfaces during the EDM process. Pure silver and copper tools with a diameter of 2 mm are used to modify surfaces of Ti6Al4V workpieces at a discharge energy of 125 µJ with different polarities. Results show that the assistance by magnetic field significantly increases the content of transferred material from tool electrode to the workpiece surface. Additionally, it increases material removal rate and reduces the modified layer thickness. Magnetic field assisted EDM is a potential technology for improving the efficacy of the EDM surface modification. © 2024 The Authors. Published by Elsevier B.V.

关键词： Titanium alloys

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Method for Evaluating and Identifying Energy-Efficient Process Chains for the Manufacturing of Press Hardening tools Based on the Deming Circle 18th

Method for Evaluating and Identifying Energy-Efficient Proce...

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18th Global Conference on Sustainable Manufacturing, GCSM 2022

作者： Rautenstrauch, Anja Markov, Larisa Kräusel, Verena Faculty of Mechanical Engineering Institute for Machine Tools and Production Processes Professorship for Forming and Joining Technische Universitaet Chemnitz Reichenhainer Str.70 Chemnitz09126 Germany Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Straße 88 Chemnitz09126 Germany

ISBN: (纸本)9783031288388

In response to rising energy demand, climate change and resource scarcity, the German government has set guiding targets for the transformation of energy systems by 2050. One goal is to increase energy efficiency in order to halve the demand for energy. An important instrument for increasing energy efficiency and reducing energy costs is the energy audit. By determining how much energy is consumed in which areas of the company, it is possible to identify where there is potential for savings. This paper presents an evaluation method for identifying energy-efficient process chains for the production of press hardening tools. The evaluation method is based on the Deming Circle and is intended to serve as a supporting tool for the energy audit. The method enables the analysis and evaluation of energetic variables of a process chain and is designed for manufacturing companies. © 2023, The Author(s).

关键词： Energy utilization

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Coupled CFD model of tool environment and workspace to determine the convective heat transfer in jet cooling of milling processes in machine tools 20

Coupled CFD model of tool environment and workspace to deter...

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20th CIRP Conference on Modeling of Machining Operations in Mons, CIRP CMMO 2025

作者： Brier, Steffen Geist, Alexander Glänzel, Janine Naumann, Christian Regel, Joachim Dix, Martin Ihlenfeldt, Steffen Chemnitz University of Technology Professorship Production Systems and Processes Reichenhainer Str. 70 Chemnitz09126 Germany Fraunhofer-Institute for Machine Tools and Forming Technology IWU Reichenhainer Str. 88 Chemnitz09126 Germany Technical University Dresden Institute for Machine Tools Development and Adaptive Controls Helmholtzstraße 10 Dresden01069 Germany

The responsible use of resources is an essential part of the manufacturing of industrial products. This includes the economical use of cooling lubricant and requires precise knowledge of the cooling mechanisms and their effect on the accuracy of the machine tool and thus the thermal error. A temporal and spatial resolution of the dynamic coolant flow near the tool and in the entire workspace in a single model would require a large simulation time. Therefore, a composite model was developed, that consists of a near-tool model and a larger surrounding workspace model. The required static near-tool cooling lubricant distribution is obtained via data discretization methods from a separate static simulation that resolves the turbulence of the cooling lubricant created by the tool rotation. The identified coolant distribution is integrated into a CFD near-tool model (with simplified tool geometry) which is coupled with a surrounding CFD workspace model. The workspace model is thus able to identify the effects of the coolant wetting on the machine surface temperature and finally, using thermo-elastic FEM simulations, on the resulting thermal error. This approach allows the composite model to simulate the entire workspace with reduced simulation effort and map the coolant-influenced heat transfer coefficients on the machine surface. © 2025 The Author(s).

关键词： Milling machines

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Silver-integrated EDM processing of TiAl6V4 implant material has antibacterial capacity while optimizing osseointegration

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Bioactive Materials 2024年第1期31卷 497-508页

作者： Hilmar Büssemaker Ann-Kathrin Meinshausen Viet Duc Bui Joachim Döring Vadym Voropai Adrian Buchholz Andreas J.Mueller Karsten Harnisch André Martin Thomas Berger Andreas Schubert Jessica Bertrand Department of Orthopaedic Surgery Otto-von-Guericke University MagdeburgGermany Professorship Micromanufacturing Technology Chemnitz University of TechnologyChemnitzGermany Institute of Molecular and Clinical Immunology Otto-von-Guericke University MagdeburgGermany Health Campus Immunology Infectiology and InflammationOtto-von-Guericke University MagdeburgMagdeburgGermany Institute of Materials and Joining Technology Otto-von-Guericke UniversityMagdeburgGermany Fraunhofer Institute for Machine Tools and Forming Technology ChemnitzGermany

Periprosthetic joint infections(PJI)are a common reason for orthopedic revision *** has been shown that the silver surface modification of a titanium alloy(Ti-6Al-4V)by PMEDM(powder mixed electrical discharge machining)exhibits an antibacterial effect on Staphylococcus *** the thickness of the silver-modified surface influences the adhesion and proliferation of bacteria as well as the ossification processes and in-vivo antibacterial capacity has not been investigated ***,the aim of this work is to investigate the antibacterial effect as well as the in vitro ossification process depending on the thickness of PMEDM silver modified *** attachment of *** on the PMEDM modified surfaces was significantly lower than on comparative control samples,independently of the tested surface *** proliferation,however,was not affected by the silver content in the surface *** observed a long-term effect of antibacterial capacity in vitro,as well as in *** induction of ROS,as indicator for oxidative stress,was observed in the bacteria,but not in osteoblast-like *** influence on the in vitro osteoblast function was observed,whereas osteoclast formation was drastically reduced on the silver *** changes in cell death,the metabolic activity and oxidative stress was measured in *** show that already small amounts of silver exhibit a significant antibacterial capacity while not influencing the osteoblast ***,PMEDM using silver nano-powder admixed to the dielectric represents a promising technology to shape and concurrently modify implant surfaces to reduce infections while at the same time optimizing bone ingrowth of endoprosthesis.

关键词： alloy silver powder

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Electrochemical material removal characteristics of a NdFeB permanent magnet 22

Electrochemical material removal characteristics of a NdFeB ...

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22nd International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2022

作者： Petzold, Tom Martin, André Schubert, Andreas Chemnitz University of Technology Institute for Machine Tools and Production Processes Professorship Micromanufacturing Technology Reichenhainer Str. 70 Chemnitz09126 Germany Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Str. 88 Chemnitz09126 Germany

ISBN: (纸本)9781998999118

Electric motors are used in various fields with an ever-increasing demand. In the electromobility sector as an example, a growth of a few hundred thousand motors per year is stated. In many cases, the rotor magnets for electric drives are produced by sintering. Special drives for two-axes positioning with precise movements require individual geometries of the rotor magnets such as spherical shapes. In this case, post-processing of the usually cylindrical or rectangular block shaped bar magnets is necessary. One common technique for post-processing is electrical discharge machining (EDM), which allows the machinability of hard or brittle materials, but also causes thermal impacts, which influence the magnetic properties of the material in a negative way. To overcome this negative effect it is necessary to re-magnetize the rotor magnets after EDM. Additional measurements of the magnetic field strength are required to ensure correct values. Electrochemical machining (ECM) represents an alternative technique for post-processing of rotor magnets, since it offers the possibility to avoid re-magnetization after the shaping process, because machining temperatures are well below the Curie temperature of most materials. In this study, ECM of a NdFeB permanent-magnetic material is presented. The experiments were carried out according to DIN-SPEC 91399. The material-specific removal characteristics indicate an active dissolution with the chosen machining parameters. Comparative measurements of the magnetic field strength before and after ECM indicate that there is no negative influence of the removal process. The results suggest that ECM with pulsed current and oscillating tool cathode is an applicable technique for shaping rotor magnets. © European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 22nd International Conference and Exhibition, EUSPEN 2022. All rights reserved.

关键词： Neodymium alloys

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Investigation of Surface Characteristics in Magnetic Field assisted Electrical Discharge Machining

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Procedia CIRP 2024年 123卷 416-421页

作者： Viet D. Bui André Martin Thomas Berger Andreas Schubert Chemnitz University of Technology Professorship Micromanufacturing Technology Reichenhainer Str. 70 09126 Chemnitz Germany Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Str. 88 09126 Chemnitz Germany

关键词： EDM magnetic field deposition modified surface

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Concentric jet for confined mask-less anodic dissolution and oxidation of aluminium 23

Concentric jet for confined mask-less anodic dissolution and...

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23rd International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2023

作者： Martin, André Quitzke, Susanne Morgenstern, Roy Schubert, Andreas Lampke, Thomas Chemnitz University of Technology Institute for Machine Tools and Production Processes Professorship Micromanufacturing Technology Reichenhainer Str. 70 Chemnitz09126 Germany Chemnitz University of Technology Institute of Materials Science and Engineering Materials and Surface Engineering Erfenschlager Str. 73 Chemnitz09125 Germany Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Str. 88 Chemnitz09126 Germany

ISBN: (纸本)9781998999132

Anodic oxide layers are established for wear and corrosion protection of surfaces of aluminium parts and for decoration purposes. Usually, anodizing is carried out in large scale on the whole part surface or locally by masking through immersion in an electrolytic bath. Applying a free jet of electrolyte offers laterally confined anodizing without extensive efforts for masking and enables local functionalization without undesired influence on the surrounding surfaces in a resource- and energy-efficient process. However, the high ohmic resistance of anodic oxides leads to a wide distribution of the current density hindering laterally confined anodizing. More sharp-contoured anodic oxides are aspired through dilution of the electrolyte film flowing off laterally from the aluminium surface. For this purpose, a concentric arrangement of an electrolyte jet surrounded by a jet of deionized water was realized. Investigations on the distribution of electric current density were carried out by electrochemical machining experiments (Jet-ECM). The application of an actively anodic dissolving electrolyte of NaCl indicates the widening of the current density distribution in terms of pitting corrosion. Compared to the free electrolyte jet surrounded by atmospheric air, a wider current density distribution was detected when applying a concentric jet of deionized water. But the shape of the dissolved cavities was not widened, which indicates only low current density values on the surrounding surface. Verification experiments on anodization confirm the comparably strong localization of anodic oxides with concentric jet and an increase in thickness compared to the results with free electrolytic jet. It was found that this is mainly because of the high ohmic resistance of the anodic oxide formed on the surrounding surface and its increasing resistance at farther lateral distance from the jet due to stronger electrolyte dilution. © 2023 Euspen Headquarters.

关键词： Electrolytes

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Developments in Powder Mixed EDM and its perspective Application for targeted Surface Modification 15

Developments in Powder Mixed EDM and its perspective Applica...

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15th CIRP Conference on Intelligent Computation in Manufacturing Engineering, CIRP ICME 2021

作者： Schubert, Andreas Bui, Viet D. Schaarschmidt, Ingo Berger, Thomas Martin, André Chemnitz University of Technology Professorship of Micromanufacturing Technology Reichenhainer Strasse 70 Chemnitz09107 Germany Fraunhofer Institute for Machine Tools and Forming Technology Reichenhainer Str. 88 Chemnitz09126 Germany

Although widely studied over the few decades, there are conflicting theories on the discharge mechanisms of powder mixed electrical discharge machining (PMEDM). Additionally, the dielectric flow plays a vital role in the distribution of powder particles in the machining gap, which significantly affects the powder deposition to the modified surface. In this paper, the literature on PMEDM surface modification is thoroughly reported. The conflicting mechanisms and the effects of PMEDM main machining conditions, such as powder and electrical parameters on improving mechanical and antibacterial properties as well as biocompatibility of the surface, have been discussed. To verify the separation mechanism of the discharge in PMEDM, single discharge investigations have been performed when silver nano-powder is mixed into the hydrocarbon-based dielectric fluid to modify Ti6Al4V surfaces. Surface topography, chemical composition as well as the deposited silver content and distribution over the crater surface when using positive and negative polarities are analyzed and discussed. Current waveforms of PMEDM and EDM without powder at varying discharge energies as well as with and without ultrasonic vibration assistance are recorded and analyzed. For the transfer of fundamental results to a perspective application, CFD simulation is used to calculate the flow field of the dielectric fluid and analyze the velocity and distribution of the nano-powder within the working gap of a setup with internal flushing. The results show that PMEDM is a potential technology for machining medical devices with simultaneous antibacterial surface modification. © 2022 The Authors. Published by Elsevier B.V.

关键词： Titanium alloys

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