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Discharge energy based optimisation of sinking EDM of cemented carbides

Procedia CIRP 2022年 108卷 734-739页

作者： T. Petersen U. Küpper A. Klink T. Herrig T. Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstr. 17 52074 Aachen Germany

The Electrical Discharge Machining (EDM) of cemented carbides is anticipated to enhance in order to allow more efficient machining. However, it is important that an optimisation does not deteriorate the surface integrity of the cemented carbide workpiece, since they are particularly sensitive to tensile stresses as they are caused by EDM. In order to allow for a safe optimisation, the surface integrity of every machining step has been examined before the optimisation regarding surface roughness, recast layer, heat affected zone and crack length. The same parameters have been examined for the optimised machining steps and the resulting workpiece. It was found that machining can be shortened without a significant detrimental effect.

关键词： EDM cemented carbide optimisation

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Advancing electrochemical machining by the use of additive manufacturing for cathode production

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Procedia CIRP 2022年 112卷 328-333页

作者： Lukas Heidemanns Tim Herrig Andreas Klink Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

The emergence of additive manufacturing (AM) technology creates promising new possibilities for the tool design in established manufacturing technologies. In electrochemical machining (ECM) it enables the integration of complex flow channels into the cathode whereby new electrolyte flushing concepts can be realized. Therefore, cathodes with three different flow channel geometries where manufactured by AM and applied in ECM. It was found, that the different designs have a significant influence on the accuracy of the machined workpieces. Finally, CFD simulations of the electrolyte flow could identify the underlying mechanism for the formation of the observed deviations.

关键词： ECM additiv manufacturing CFD cavitation

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Thermographic in-situ investigation of precise electrochemical machining

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Procedia CIRP 2022年 113卷 404-409页

作者： L. Heidemanns T. Herrig A. Klink T. Bergs Laboratory for Machine Tools and Production Engineering WZL of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

Modelling of ECM is a powerful tool to improve the cost- and time intensive tool-development process. While different simulation models for DC-ECM have been published and validated, the virtual prediction of the process variant with oscillating cathode is still hindered by its highly transient nature. In order to develop and later validate a model of PECM, high-resolution information on the temperature profile and gas evolution during one oscillation is required. Temperature and gas concentration both increase during the electric pulses and constantly decrease due to flushing. This paper presents a fixture that allows the thermographic analyses of the PECM process. Consequently, the conditions within the electrolyte channel during PECM are captured which allows a deeper understanding of the process.

关键词： PECM thermography ECM

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Influence of Electrical and Thermal Conductivity of Cemented Carbides on the Wire EDM Process

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Procedia CIRP 2022年 113卷 53-58页

作者： M. Olivier U. Küpper T. Herrig A. Klink T. Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstraße 17 52074 Aachen Germany

Wire electrical discharge machining (WEDM) is suitable for manufacturing fine blanking punches made of cemented carbides, because it is independent of the mechanical material properties. Nevertheless, the process is influenced by electrical and thermal properties of the machined workpiece and the properties of the used dielectric. Cemented carbides differ in their thermal and electrical properties depending on grain size and binder content. This leads to instabilities or wire breakages during the machining when using standard machining technology. To avoid this, the electrical machine settings must be adapted to the respective material. So far, there is no physical material-property-based approach, which allows a material-specific adaptation of the machine settings. Therefore, in this paper, the influence of the material properties in combination with the used dielectric on the process conditions during WEDM is investigated. For this purpose, nine carbides with different electrical and thermal conductivities (varying binder content and grain size) are investigated in two oil-based and in two water-based dielectrics. It could be observed, that with increasing thermal and electrical conductivity of cemented carbides the cutting rate decreases, when not adapting the machine settings. Individual adaptation of the machine settings to the respective cemented carbides composition significantly increased the cutting rate. Furthermore, when using a high viscosity dielectric with low thermal conductivity, the highest cutting rate is observed. The resulting higher heat concentration is assumed to be the cause based on the measured discharge craters and the rim zone thicknesses.

关键词： WEDM Dielectrics Cemented Carbides

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Investigation of residual stresses and workpiece distortion during high-feed milling of slender stainless steel components

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Procedia CIRP 2022年 108卷 495-500页

作者： Hui Liu Daniel Schraknepper Thomas Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstr. 17 52074 Aachen Germany

In high-feed milling, the workpiece surface is subjected to high thermo-mechanical loads, which leads to excessive changes in residual stresses and thus affects the quality of the product. In this work, the influence of tool geometry and cutting speed on the residual stress state and the resulting workpiece distortion was investigated. Machining tests were performed by face milling of slender parts made of low sulfur stainless steel X2CrNiMo17-12-2. The results showed that the macro-geometry of the tool has a major influence on the surface topography and residual stresses. The cutting edge radii have barely any influence on the residual stresses under the conditions investigated.

关键词： high-feed milling residual stress stainless steel

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Surface modification for SMC moulding tools by laser remelting 19

Surface modification for SMC moulding tools by laser remelti...

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19th International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2019

作者： Gärtner, E. Vogel, M. Schneider, J. Edelmann, J. Fraunhofer Institute for Machine Tools and Forming Technology IWU Chemnitz Germany

ISBN: (纸本)9780995775145

Due to their excellent material properties and their largely adjustable functionality, duromer components made of SMC (sheet moulding compound), which are mass-produced by compression moulding, are used in an increasing number of industries. Despite intensive development work in the field of stable production processes in compression moulding and a high-quality topcoat, the economic damage caused by paint failures is still very high at 20-30 %. Both, the demoulding process of the SMC components and their paintability are significantly influenced by the surface structure/topography of the moulding tool. One method of targeted layer modification is laser remelting. The paper presents the possibilities of laser remelting with a 20 W fiber laser by IPG Laser GmbH in detail. In the course of this, the influence of the inert gas use will be explained and a process chamber developed for this task will be evaluated. The processing results for hardened and tempered as well as soft annealed cold work steel are compared. Moreover, the influence of the laser processing on the heat treatment is derived. The residual surface was characterized and investigated by SEM (scanning electron microscopy) and EDX (energy dispersive X-ray spectroscopy). Furthermore, measurements of microhardness and surface roughness were performed. © 2019 European Society for Precision Engineering and Nanotechnology, Conference Proceedings - 19th International Conference and Exhibition, EUSPEN 2019. All rights reserved.

关键词： Scanning electron microscopy

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Investigation of the micro hardness at the cut surface of fine blanked parts with variation of sheet material and cutting temperature 19th

Investigation of the micro hardness at the cut surface of fi...

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19th International Conference on Sheet Metal, SheMet 2021

作者： Weiser, Ingo Felix Feuerhack, Andreas Bergs, Thomas Laboratory for Machine Tools and Production Engineering WZL RWTH Aachen University Campus-Boulevard 30 Aachen52074 Germany Fraunhofer-Institute for Production Technology IPT Steinbachstr. 17 Aachen52074 Germany

ISBN: (纸本)9783035716931

Fine blanking is a production technology of high importance especially for the automotive industry. As a procedure of sheet metal separation, it is possible to produce complex parts in a single stroke. As a difference to conventional punching, the cutting surface of fine blanked parts can often be used as a functional surface without further process steps. However, fine blanking as a forming process changes the microstructure of the metal sheet to a higher extend than cutting or machining processes. Due to this, it is of utmost importance to investigate the cause-effect-relations between the fine blanking process parameters and the resulting properties of the fine blanked part. Especially the condition of the cut surface as an important quality criterion has to be investigated. The quality characteristics of the cut surface of fine blanked parts are often subject of investigations. In addition, it would be of importance to investigate how the material properties in the shear zone are changed by the fine blanking process. This on one hand in turn can enable conclusions to be drawn about possible punch wear. If, on the other hand, hardening of the cut surface takes place as a result of fine blanking, then this could have a positive influence on the application properties of fine blanked components. Thus, an experimental fine blanking investigation of the micro hardness of the cutting surface has been made with variation of steel material and cutting temperature. It could be demonstrated that the micro hardness increases in direction towards the burr. This is independent on material and cutting temperature. © 2021 Trans Tech Publications Ltd, Switzerland.

关键词： Microhardness

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Mass Loss and Displacement Modeling for Multi-Axis Milling

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Procedia CIRP 2023年 120卷 1534-1539页

作者： Adrian Karl Rüppel Patrick Ochudlo Mathias Bickel Sebastian Stemmler Thomas Bergs Dirk Abel Laboratory for Machine Tools and Production Engineering (WZL) RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Institute of Automatic Control (IRT) RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology (IPT) Steinbachstraße 17 52074 Aachen Germany

During the cutting process, material of the workpiece is continuously being removed by the cutting tool, which results in a reduction of mass as well as a displacement in the center of the workpiece mass. When using workpiece sided force sensors, such as table dynamometers, the total mass and the displacement of the center of mass affects the force measurement due to gravitational and inertial effects. The high flexibility of the milling process leads to a complex change of volume and mass and necessitates the consideration of the engagement conditions between tool and workpiece along the tool path in order to estimate changes in mass and center of mass. This paper proposes a method for estimating the mass loss and the displacement of the center of mass during multi-axis milling processes. In this method the tool gets numerically sliced along the tool axis and the workpiece removal for each slice along an arbitrary tool path gets calculated. To validate the mass loss model, experiments in both three-axis milling as well as multi-axis milling processes have been conducted. Since it is difficult to measure the center of mass, validation for the displacement of the center of mass was done by comparison with data extracted from CAD. The results show good agreement between the simulated and measured mass loss using the proposed approach.

关键词： milling mass change center of mass

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Descriptive Analysis of the Multisensory Properties and Quality Perception of Sustainable Plastic Alternatives

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Procedia CIRP 2022年 112卷 537-542页

作者： F. Sohnius L. Gussen N. Viktorov Raphael Kiesel Robert H. Schmitt Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstr. 17 52074 Aachen Germany

This paper presents the results of an equivalence analysis of conventional and bio-based plastics based on a consumer study using Perceived Quality as a measure. The mass use of non-recyclable plastics poses an immense ecological problem. Due to their importance in consumer and industrial products, plastic use cannot be completely eliminated, however, bio-based alternatives are increasingly available. In order to strengthen the acceptance of these "bioplastics", especially in visible and tactile product areas, the sensory properties must be precisely determined and specified.

关键词： Sustainability Perceived Quality Plastics Bioplastics

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Effects of the Manufacturing Chain on the Surface Integrity when Machining Fir Tree Slots with Alternative Manufacturing Processes

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Procedia CIRP 2022年 108卷 728-733页

作者： U. Küpper T. Seelbach L. Heidemanns S. Prinz T. Herrig T. Bergs Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University Campus-Boulevard 30 52074 Aachen Germany Fraunhofer Institute for Production Technology IPT Steinbachstr. 17 52074 Aachen Germany

The use of materials with increasing thermo-mechanical strengths for turbine disks and new designs inducing filigree geometries bring conventional manufacturing processes to their technical and economical limits. Investigations regarding alternative manufacturing technologies showed advantages compared to conventional broaching with high-speed steel (HSS) cutting tool material. Surface integrity is particularly crucial for the technological evaluation. However, this aspect has not been considered after downstream processes in which the machined surface integrity is modified. Therefore, the surface integrity of Inconel 718 machined by alternative manufacturing processes including wire EDM, ECM and broaching with cemented carbide is investigated after downstream processes, etching and shot peening.

关键词： Surface integrity Manufacturing process Residual stress

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