The Study of Polymer Electro-rheological Fluid for EDM-Polishing Process

• Main Authors: Chih-Kang Chang, 張志綱
• Other Authors: 蔡曜陽
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/37474415079834835611

碩士 === 國立臺灣大學 === 機械工程學研究所 === 96 === Electrical discharge machining (EDM) is an important manufacturing process for mold and die. However, the work-piece surfaces after EDM process have the defects, such as micro-craters and white layer (recast layer). Therefore, the polishing is usually required after EDM process. This study presents a novel method of EDM that used Electro-rheological polishing fluid (ERP fluid) instead of conventional EDM oil. When applying high electric field between the electrode and work-piece, the dielectric particles are polarized and then the ER fluid will transform into fibrous chains. The fibrous chains seem to be working as polishing brushes dragging abrasive to carry out net shape by combining EDM and polishing in one process. In this study, the ER fluids were composed of polyaniline (PANI) or starch particles suspending in silicone oil. We first discussed EDM effects of ER fluids and compared it with conventional EDM oil. The surface roughness and material removal rate (MRR) in ER fluid are worse than EDM oil, but the workpiece surface is impinged by silicone, which can improve hardness and anti-corrosion of work-piece. In the experiments of ERP fluid mixing abrasive and ER fluid, using ER-abrasive ratio of 1:1 and negative electrode can obtain better surface roughness. We had the best machined surface without white layer and surface roughness of Ra 0.10μm when the starch concentration was 100g/L. There is 86% improvement of surface roughness from Ra 0.69μm for conventional EDM oil. Based on electro-rheological test, we found out starch is the most suitable particle for EDM-polishing because it has the largest shear stress and the highest breakdown electric field strength. This study successfully developed a novel ERP fluid using starch and alumina particles to carry out the combined process of EDM and polishing. Moreover, this study also indicates the key properties of ER fluid for EDM-polishing process.