No description available.

Water-repellent behaviour, known as hydrophobicity, has recently attracted a great deal of interest due to its applications, such as anti-icing and self-cleaning. The phenomenon of hydrophobicity found in surfaces like lotus leaves is manifest by a hierarchical structure on low-energy surfaces. Fabrication of hydrophobic surfaces has thus far been largely accomplished on polymers and colloidal materials, which are limited by poor mechanical strength that leads to performance degradation over time. To this end, fabrication of a robust metallic hydrophobic surface is the focus of this research. Sink electrical discharge machining is demonstrated to generate hydrophobic surfaces in 7075 aluminum alloy with water contact angles in excess of 150˚. / Thesis / Master of Applied Science (MASc)

Self-excited vibration, known as chatter, limits material removal rate, surface finish and accuracy in machining, and may even cause structural damage to components of the machining system. Machining stability may be enhanced by a variety of methods, from moving machining parameters to stable regions, or using actively actuated tools specially designed to obstruct self-excitation, or even by passively enhancing the stiffness or damping of the system as to soften the critical mode of vibration. Although there are many approaches to reduce chatter, not all of them are always effective in every situation. Moving machining parameters is restricted by workpiece machinability. Active damping mechanisms require large contraptions to function and have limited effectiveness when dealing with high frequency chatter. Passive damping approaches have essentially entailed tuned mass dampers which require delicate finetuning and drastic alterations to the tool structure in order mount the vibration absorber system. This research presents an elegant and innovative application involving electrical discharge texturing for chatter suppression that takes advantage of frictional forces to passively damp self-excited vibrations. This technique proved effective in a frequency range from 100 to 4000 Hz achieving damping enhancements of more than 400% without the need of any tuning and showing repeatable damping values after subsequent assembly and disassembly cycles. When applied to a grooving operation the technique proved effective in increasing the limiting width of cut by more than 120%. / Thesis / Master of Applied Science (MASc)

The presented diploma thesis deals with the issue of wire electrical discharge machining of SiSiC ceramics. The first part explains the principles of electrical discharge machining, describes the WEDM technology and presents the properties of the advanced ceramics. The second part consists of a detailed analysis of the cutting process of eighteen samples obtained with systematically changing process parameters. Based on the obtained results from EDX analysis, SEM electron microscopy and topography there was performed an analysis of the influence of process parameters on the cutting speed, surface roughness, kerf width and number of wire breaks with usage of the selected brass cutting wire. From the evaluated results it was possible to select a combination of parameters that ensured a stable machining process.

The aim of this dissertation are future trends of electrical discharge machining in conditions of a small tool factory. In the introduction is presented the theory of non-conventional machining. The practical part is focused on valuation the current level of electrical discharge machining, the importance of the use in a tool Nástrojárna Ryšavý. It also compares the level of leading global manufacturers of electrical discharge machines and future trends of electro-discharge technology.

Wire electrical discharge machining (WEDM) is a precision machining process that uses electrical discharges struck between an axially moving wire electrode and the workpiece to remove material through melting and vaporization. WEDM is replacing traditional processes like broaching for machining safety-critical components such as the turbine disk in the manufacture of fuel-efficient jet engines. The main issue preventing the more widespread use of WEDM is that due to WEDM being less productive than broaching, it currently requires 6 WEDM machine tools to replace a single broaching machine to maintain the same throughput. The main factor limiting WEDM productivity is wire breakage. To increase the Cutting Rate (CR) more power is required, and increasing power also increases the likelihood of breakage. The goal of this research is to determine whether wires thicker than the conventional 0.25 mm diameter will both optimize the cutting rate and minimize breakage. Thicker wires will allow for an increase in the duty factor, with a significantly decreased incidence of wire breakage. Given that an increased wire diameter also increases the kerf width, this research seeks to identify the optimal wire diameter that maximizes the linear cutting rate. This research concluded that using wire of optimal diameter in WEDM increases the CR by as much as 400%. / Thesis / Master of Science in Mechanical Engineering (MSME) / In order to secure jet engine blades onto the engine, complex features called Firtree Root Forms (FTRF) are used. These features need to be very precisely cut in order for the engine to work at peak efficiency. Currently, industry is using a manufacturing process called broaching to machine these FTRFs, however broaches wear out over time, which causes imprecise cuts. The solution to this is to use Wire Electrical Discharge Machining (WEDM). The problem with WEDM is that it takes on average 6 machines to replace a single broaching machine in terms of productivity. The objective of this project is to increase the cutting speed (and thus productivity) of WEDM, and one of the ways to do that is to increase the electrode wire diameter. This allows for more power to be used in the machining process without the risk of wire breakage, which is a major problem when cutting with WEDM. The research presented in this thesis successfully demonstrates that using thicker wires in WEDM can cut as much as 400% faster than the wires currently in common use in industry.

<p>Electrical discharge machining (EDM) is a non-conventional machining process in which material removal is accomplished through spark erosion between a workpiece and tool electrode. Process stability is of great importance to the productivity of the EDM process, especially in the wire EDM configuration where an unstable process could lead to wire breakage having a detrimental effect on productivity. This thesis investigates the application of acoustic emission (AE) in EDM as a process monitoring technique. AE techniques have been applied to almost all machining processes; however its benefit as applied to EDM has not been investigated yet. The AE signal from the EDM process is related to various EDM parameters including, electrical parameters, tool materials, flushing and some process modifications, such as dispersing metallic powder into the gap. Using this knowledge, the benefits of using an AE sensor for a real-time process monitoring technique have been proven.</p> / Master of Applied Science (MASc)

This marter’s thesis deals with the technology of electrical discharge wire cutting. There is described the basic nature of the electrical erosion, EDM principle and WEDM principle. The main part deals with the application of wire cutting in the manufacture pulley 68-8M-130 with a description of technology on the wire cutter Excetek V 650. At the end of the work is devoted to the statistical evaluation of the precision machined surfaces.

This master´s thesis focuses on the basic principles of the nonconventional technology of electrical discharge machining (EDM) with an emphasis on wire-cut electrical discharge machining performed in a mediumsized company. The thesis deals with manufacture of a belt pulley 75-8M-130, and checks of accuracy of wire-cut EDM machines. Following the study of the current status of electrical discharge machining in the engineering company, measures for assurance and increase of accuracy of wire-cut EDM machines are proposed.

My thesis is aimed at the application of wire electical discharge machining technology in the production of woodworking tools. All of this in the conditions of Vydona company. There is a theory of machining method plus a well-aranged division of cutter tools for wood in the introduction. The practical part describes in detail the procedur of cutting shaped plate out of tungsten carbide. As a result of the technical and at the same time the economic evaluation is an establishment of hourly rate for machine.