Cold Micro Metal Forming

This open access book contains the research report of the Collaborative Research Center “Micro Cold Forming” (SFB 747) of the University of Bremen, Germany. The topical research focus lies on new methods and processes for a mastered mass production of micro parts which are smaller than 1mm (by forming in batch size higher than one million). The target audience primarily comprises research experts and practitioners in production engineering, but the book may also be of interest to graduate students alike

Process analysis and design in micro deep drawing utilizing a flexible die

As a result of the remarkable demands on electronic and other portable compact devices, the need to produce various miniaturized parts, particularly those made from metallic sheet is growing. In other words, in order for manufacturing companies to stay in competition, they are required to develop new and innovative fabricating processes to produce micro components with more complex features and a high standard of quality and functionality. Microforming is a micro fabrication process that can be employed efficiently for mass production with the advantages of greatly minimizing material waste and producing highly accurate product geometry. However, since the clearance between the rigid tools, i.e. punch and die, utilized in microforming techniques is relatively very small, there is a high risk of damaging the tools during the forming operations. Therefore, the use of forming tools made of flexible materials in sheet metal forming processes at micro scale has powerful potential advantages. The main advantages include a reduction in the production cost, eliminating the alignment and mismatch difficulties, and also the creation of parts with different geometrical shapes using the same flexible tool. As the workpiece is in contact with a flexible surface, this process can significantly improve the quality of the obtained products. Despite these clear advantages, micro flexible forming techniques are currently only utilized in very limited industrial applications. One reason for this is that the deformation behaviour and failure mode of sheet metals formed at micro scale are not yet well understood. Additionally, the experience-based knowledge of the micro-forming process parameters is not sufficient, particularly when flexible tools are used. Hence, to advance this technology and to improve the production quality of formed micro parts, more investigation of the key process parameters related to the material deformation are needed. The main contribution of this work is the development of a novel technique for achieving micro deep drawing of stainless steel 304 sheets using a flexible die and where an initial gap (positive or negative) is adopted between the blank holder plate and an adjustment ring utilized in the size-scaled forming systems developed for this purpose. The interesting point here is that this study presents the first attempt of employing flexible material as a forming die tool in the micro deep drawing technology to produce micro metallic cups at different scaling levels. Polyurethane rubber materials are employed in this study for the forming flexible die with various Shore A hardness. Also, the stainless steel 304 sheets utilized for the workpieces have different initial thicknesses. Various parameters that have a significant influence on the sheet formability at micro scale are carefully considered, these include initial gap value, rubber material properties, initial blank thickness, initial blank diameter, friction coefficients at various contact interfaces, diameter and height of the rubber die and process scaling factor. The size effect category of process dimension was also taken into account using similarity theory. Three size-scaled micro deep drawing systems were developed correspondingly to three different scaling factors. In each case, finite element simulations for the intended micro drawing systems are performed with the aim of identifying optimum conditions for the novel forming methodology presented in this thesis. The numerical models are built using the known commercial code Abaqus/Standard. To verify the microforming methodology adopted for the proposal technique as well as to validate the predictions obtained from simulations, an appropriate number of micro deep drawing experiments are conducted. This is achieved using a special experimental set up, designed and manufactured to fulfil the various requirements of the micro-forming process design procedure. The new knowledge provided by this work provides, for the first time, a predictive capability for micro deep drawing using flexible tools that in turn could lead to a commercially viable production scale process

Magnetron sputtered thin films and composites for automotive and aerospace electrical insulation

Ceramics are highly prised as insulating materials because of their high stability under demanding conditions (thermal, chemical and radiological). However, the use of ceramics as wire insulation is currently limited to powder packed and relatively thick low voltage coatings. This work follows the development of sputtered Al2O3 and Al2O3, SiO2 and Ta2O5 composite films as deposited onto copper. Copper disk studies will ultimately be translated onto Cu wire for a proof of concept study. Initial Al2O3 deposition utilised RF or DC sputtering but this found to have low deposition rate (up to 16 nmh 1) and to contain crystallite and metallic defects (up to 19.6 at. % Al0) respectively. These issues were addressed by introducing pulsed DC (PDC) deposition conditions, producing films with no crystalline or metallic defects (up to 146 nmh 1). The dielectric strength of PDC films measured by AFM time dependant dielectric breakdown was 310 ± 21 Vμm 1, higher than that of the DC deposited films which had a dielectric strength of between 165 ± 19 and 221 ± 20 Vμm 1. A dielectric strength of 310 Vμm 1 is suitable for applications with a voltage rating below 150 V and is also a good platform for the production of higher quality coatings. The mechanical properties of the films did suffer from a lower amount of blending at the interface, DC pull off strength was 25.8 ± 9.8 - 72.3 ± 5.6 MPa with the PDC pull off strength being 55.7 ± 2.9 MPa). Wires coated with such PDC Al2O3 showed promise with full circumference coating, however, short circuiting was apparent in the wires potentially caused by micro cracking induced either during or post deposition. The use of multilayer composites consisting of the aforementioned PDC Al2O3 and RF SiO2 or RF Ta2O5 resulted in significant gains with respect to the material’s electrical properties. The films deposited with 2 layers of each PDC Al2O3 and the RF addition performed best in terms of dielectric strengths of 513 ± 18 and 466 ± 86 Vμm 1 for Ta2O5 and SiO2 composites respectively. The success of the 2x2 layer configuration resulted from a compromise between the number of RF layers and their thickness. The mechanical properties did, however, suffer as a result of increased intrinsic stress caused by the use of multilayers of materials with varying expansion coefficients, reducing pull off adhesion strength to a maximum of 34.4 ± 4.4 MPa, where ideally the pull off adhesion would be above 80 MPa. Heat treatment of these coatings resulted in decreased adhesive properties, with a maximum pull off adhesion strength of 20.1 ± 0.9 MPa being apparent. Most of the electrical properties remained the same or were decreased by heat treatment, however the dielectric strength of the SiO2 composites improved by an average of 12 % resulting in a maximum dielectric strength of 517 ± 24 Vμm 1 due to a reduction in the defect density in the films. Conversely the electrical properties of Ta2O5 composites suffered greatly following heat treatment with a maximum dielectric strength of 358 ± 31 Vμm 1. This was theorised to result from Cu migration from the substrate and the potential for Ta2O5 to crystallise at temperatures close to 500 °C. Coating of Cu wires with PDC alumina was shown to be possible, with coatings of various interlayer and coating thickness. Characterisation showed that the wire coating rig enabled the whole circumference of the wire to be coated with alumina. Tensile testing resulted in transvers cracking followed by longitudinal cracking above an applied strain of 1.5 and 4.0 % respectively. Following heat treatment the copper substrate softened and resulted in delamination failures in the coatings during tensile testing. Electrical testing of the wires was inconsistent due micro cracking in the wire coatings. It has been shown that the use of mixed material composites sputtered by PDC and RF sputtering have potential as high dielectric strength insulating materials, improving upon the base Al2O3 believed to be a result of passivation of structural and compositional defects. Additionally, it has been shown that physical vapour deposition in conjunction with a modified sample holder can be utilised for coating of bare copper wire with the potential to act as isolative coatings

Magnetron sputtered thin films and composites for automotive and aerospace electrical insulation

Ceramics are highly prised as insulating materials because of their high stability under demanding conditions (thermal, chemical and radiological). However, the use of ceramics as wire insulation is currently limited to powder packed and relatively thick low voltage coatings. This work follows the development of sputtered Al2O3 and Al2O3, SiO2 and Ta2O5 composite films as deposited onto copper. Copper disk studies will ultimately be translated onto Cu wire for a proof of concept study. Initial Al2O3 deposition utilised RF or DC sputtering but this found to have low deposition rate (up to 16 nmh 1) and to contain crystallite and metallic defects (up to 19.6 at. % Al0) respectively. These issues were addressed by introducing pulsed DC (PDC) deposition conditions, producing films with no crystalline or metallic defects (up to 146 nmh 1). The dielectric strength of PDC films measured by AFM time dependant dielectric breakdown was 310 ± 21 Vμm 1, higher than that of the DC deposited films which had a dielectric strength of between 165 ± 19 and 221 ± 20 Vμm 1. A dielectric strength of 310 Vμm 1 is suitable for applications with a voltage rating below 150 V and is also a good platform for the production of higher quality coatings. The mechanical properties of the films did suffer from a lower amount of blending at the interface, DC pull off strength was 25.8 ± 9.8 - 72.3 ± 5.6 MPa with the PDC pull off strength being 55.7 ± 2.9 MPa). Wires coated with such PDC Al2O3 showed promise with full circumference coating, however, short circuiting was apparent in the wires potentially caused by micro cracking induced either during or post deposition. The use of multilayer composites consisting of the aforementioned PDC Al2O3 and RF SiO2 or RF Ta2O5 resulted in significant gains with respect to the material’s electrical properties. The films deposited with 2 layers of each PDC Al2O3 and the RF addition performed best in terms of dielectric strengths of 513 ± 18 and 466 ± 86 Vμm 1 for Ta2O5 and SiO2 composites respectively. The success of the 2x2 layer configuration resulted from a compromise between the number of RF layers and their thickness. The mechanical properties did, however, suffer as a result of increased intrinsic stress caused by the use of multilayers of materials with varying expansion coefficients, reducing pull off adhesion strength to a maximum of 34.4 ± 4.4 MPa, where ideally the pull off adhesion would be above 80 MPa. Heat treatment of these coatings resulted in decreased adhesive properties, with a maximum pull off adhesion strength of 20.1 ± 0.9 MPa being apparent. Most of the electrical properties remained the same or were decreased by heat treatment, however the dielectric strength of the SiO2 composites improved by an average of 12 % resulting in a maximum dielectric strength of 517 ± 24 Vμm 1 due to a reduction in the defect density in the films. Conversely the electrical properties of Ta2O5 composites suffered greatly following heat treatment with a maximum dielectric strength of 358 ± 31 Vμm 1. This was theorised to result from Cu migration from the substrate and the potential for Ta2O5 to crystallise at temperatures close to 500 °C. Coating of Cu wires with PDC alumina was shown to be possible, with coatings of various interlayer and coating thickness. Characterisation showed that the wire coating rig enabled the whole circumference of the wire to be coated with alumina. Tensile testing resulted in transvers cracking followed by longitudinal cracking above an applied strain of 1.5 and 4.0 % respectively. Following heat treatment the copper substrate softened and resulted in delamination failures in the coatings during tensile testing. Electrical testing of the wires was inconsistent due micro cracking in the wire coatings. It has been shown that the use of mixed material composites sputtered by PDC and RF sputtering have potential as high dielectric strength insulating materials, improving upon the base Al2O3 believed to be a result of passivation of structural and compositional defects. Additionally, it has been shown that physical vapour deposition in conjunction with a modified sample holder can be utilised for coating of bare copper wire with the potential to act as isolative coatings

Nuclear Fusion Programme: Annual Report of the Association Karlsruhe Institute of Technology (KIT)/EURATOM ; January 2009 - December 2009 (KIT Scientific Reports ; 7548)

The Karlsruhe Institute of Technology (KIT) is working in the framework of the European Fusion Programme on key technologies in the areas of superconducting magnets, microwave heating systems (Electron-Cyclotron-Resonance-Heating, ECRH), the deuterium-tritium fuel cycle, He-cooled breeding blankets, a He-cooled divertor and structural materials, as well as refractory metals for high heat flux applications including a major participation in the preparation of the international IFMIF project

Nuclear Fusion Programme: Annual Report of the Association Karlsruhe Institute of Technology (KIT)/EURATOM ; January 2010 - December 2010 (KIT Scientific Reports ; 7592)

The Karlsruhe Institute of Technology (KIT) is working in the framework of the European Fusion Programme on key technologies in the areas of superconducting magnets, microwave heating systems (Electron-Cyclotron-Resonance-Heating, ECRH), the deuterium-tritium fuel cycle, He-cooled breeding blankets, a He-cooled divertor and structural materials, as well as refractory metals for high heat flux applications including a major participation in the preparation of the international IFMIF project

Remanufacturing and Advanced Machining Processes for New Materials and Components

"Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems.

Remanufacturing and Advanced Machining Processes for New Materials and Components

Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems

Remanufacturing and Advanced Machining Processes for New Materials and Components

Remanufacturing and Advanced Machining Processes for Materials and Components presents current and emerging techniques for machining of new materials and restoration of components, as well as surface engineering methods aimed at prolonging the life of industrial systems. It examines contemporary machining processes for new materials, methods of protection and restoration of components, and smart machining processes. • Details a variety of advanced machining processes, new materials joining techniques, and methods to increase machining accuracy • Presents innovative methods for protection and restoration of components primarily from the perspective of remanufacturing and protective surface engineering • Discusses smart machining processes, including computer-integrated manufacturing and rapid prototyping, and smart materials • Provides a comprehensive summary of state-of-the-art in every section and a description of manufacturing methods • Describes the applications in recovery and enhancing purposes and identifies contemporary trends in industrial practice, emphasizing resource savings and performance prolongation for components and engineering systems The book is aimed at a range of readers, including graduate-level students, researchers, and engineers in mechanical, materials, and manufacturing engineering, especially those focused on resource savings, renovation, and failure prevention of components in engineering systems