الفهرس 
CHAPTER 1: REVIEW OF PREVIOUS WORKOnly 14 pages are availabe for public view
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Abstract
Wire electro-discharge machining (WEDM) is a well established non-conventional material removal process capable of meeting the diverse machining requirements passed by the demanding metal cutting industries. It has been commonly applied for the machining and micromachining of parts with intricate shapes and varying hardness requiring high profile accuracy and tight dimensional tolerances. The ultimate goal of the WEDM process is to achieve an accurate and efficient machining operation from the infinite number of combinations. In the present investigation, response surface methodology (RSM) has been applied to analyze and optimize parameters setting in the WEDM for CK45 steel. The process performance criteria such as material removal rate, tool wear rate, and surface roughness were evaluated. Feeding speed, duty factors, water pressure, wire tension and wire speed have been considered the main factors affecting WEDM performance. Based on RSM technique, experiments have been carried out through 32 different operating parameters to anticipate the effect of each factor. Experiments have been carried out on CK45 steel. The selection of this material was made, taking into account its wide range of applications in aerospace and automotive industry. The experiments have been made on a W-B30J.S 5AXS CNC WEDM machine. Examination of the EDMed surface using Scanning Electron Microscope (SEM) revealed that surface effects include fusion, plastic deformation, waviness, overlapped craters, and surface cracks. Surface defects increase with an increase in feeding speed and duty factor. Furthermore, the effect of water pressure, wire tension and wire speed has been carefully anticipated through the SEM photographs. The surface compositions of the specimen surface were examined through Xray diffraction technique. This investigation was very helpful to explain and understand the mechanism of metal removal. Its also clarified the material of the wire that has been transferred and deposited on the workpiece surface during the WEDM process.
The results of the present work show that the feeding speed and duty factor are the most vital factors controlling metal removal rate (MRR). The effect of wire tension and wire speed on MRR was very limited and insignificant. Water pressure has been found to have a sensible effect on MRR especially at higher feeding speed. The present investigation revealed that the min. tool (wire) wear rate (TWR) has been obtained at the parametric combination of low feeding speed and low duty factor. In general, it has been found that the increase of water pressure, wire tension and wire speed decreases tool wear. However, this trend was not valid after water pressure exceeded 2.5 MPa and wire tension exceeded 2000 gf and wire speed exceeded 10 m/s. During the WEDM process of CK45 steel, fine surface texture has been recorded at lower feeding speed, lower duty factor and higher water pressure. It has also been clarified that the increase of wire tension and wire speed leads to a relatively insignificant change in surface quality.
Finally, multi-objective optimization has also been achieved to facilitate the choice of the different parametric conditions to get maximum MRR or minimum TWR or minimum surface roughness (SR), simultaneously.
Finally, the results obtained form the present investigation will provide production engineers in WEDM with some necessary information about the performance of CK45 steel.