الفهرس 
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Abstract
A numerical investigation had been conducted to study eccentricity minimization in cylindrical products which helps to reduce the mechanical vibrations and wear of related mechanical parts such as bearings, columns, gears ...etc., which positively affects maintenance cost savings and increases production quality reliability. The main purpose of this work is to investigate the effect of the eccentricity between the billet material and the die parts on the quality of the final product in the direct extrusion process. The input parameters to produce a cylindrical product shape are optimized in “MINITAB” based on Taguchi Method and ANOVA. The selected material of the billet is AA2024, and the die material is Steel H13. The inputs parameters are the temperature, the die angle, the ram speed and the presumed eccentricity. The finite element model of the process is simulated in “DFORM-3D” for providing the extrusion information such as the pressure, the effective stress and strain, the final product eccentricity and the roundness error. The study is carried out on two cases of presumed eccentricity in addition to a case of zero eccentricity. The single and multi-response optimizations are executed to obtain the optimum parameters for the minimum product eccentricity and roundness error. The single response optimization used of Taguchi method to obtain the effect of each output parameter (responses) on all input parameters. A multi-response optimization is executed to obtain the optimal process parameters were selected through the Taguchi method to determine optimum process parameters. With the use of statistical development software ””Minitab-18”” and using an L9 orthogonal array with four inputs parameters, studied and optimized process parameter has been obtained, which results in minimum product eccentricity and roundness error. The use of one-way analysis of variance (ANOVA) is to obtain the significance of each input parameter relative to each output parameter (responses) and to get the significance of all input parameters relative to each output parameter. They show that the presence of eccentricity has an active effect on the product quality. The optimal selection of the values of the parameters may help in improving the extrusion process.