الفهرس 
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Abstract
Surfaces play a major role in engineering parts. Generally, surfaces affect the functional performance of engineering parts such as lubrication, wear, and friction. Surface roughness is considered as a fingerprint of machining processes. The surface roughness generated during any machining process will depend on the nature of the process, the material removal mechanism, the levels of different process parameters, and the type and properties of the tool and workpiece materials. By evaluating or estimating different roughness parameters, a diagnosis of the condition of the machining process can be performed to assure adequate performance. Electro discharge machining (EDM) of AI203 conductive ceramic was selected due to the growing need for machining new materials having high hardness for manufacturing products such as dies and cutting tools.
In the current study, an old (obsolete) surface measuring instrument (Talysurf 4) has been upgraded to be able to produce a profile graph and estimate different roughness parameters. The Talysurf 4 instrument is interfaced with a PC computer via a data acquisition card. A software package has been newly developed for recording digitized roughness profile coordinates and assessment of roughness profile parameters. The upgraded system has been calibrated and validated.
The calibrated Talysurf 4 instrument has been used to evaluate surface roughness when machining Al203 conductive ceramic using EDM. The relationship between the surface generation mechanism and the resulting roughness profile has been considered. A set of Ah03 based ceramic samples were machined by EDM using a flat copper electrode submerged in kerosene as a dielectric fluid. A full factorial experimental design was used to investigate the effect of considered EDM process variables (factors), which include pulse-on time, pulse-off time, and pulse current on process performance measures. The considered process performance measures are; crater geometry parameters (crater diameter, crater depth, and crater volume), material removal rate (MRR), and roughness amplitude parameters (Ra, Rz, and Rt)
An ANOV A test was carried out to detennine the most significant variables (factors)! which affect different process performance measures. Empirical models have beeA developed using DESIGN EXPERT V.8 to estimate different performance measures. Pi, comparison between experimental results and corresponding empirical ones shows g agreement.
In this study, an old (obsolete) stylus type instrument (Talysurf 4) has been successfuU upgraded and interfaced with a PC computer. The upgraded system was successfully to evaluate surface roughness of conductive ceramic samples produced by EDM. Tb, investigation results proved that pulse current has the most significant effect in almost process performance measures. The considered process performance measures increase . value as the pulse -current increases, but decreases as the pulse-off time increases. ~ considered process performance measures increase as the pulse-on time increases until i reaches a specific value when it starts to decrease with further increase in the pulse time. Machining conditions which will result in optimum process performance me have been determined.