Improvement of surface integrity of electro-chemical discharge machining process using powder-mixed electrolyte

摘要

A new method has been investigated to improve the surface integrity of electro-chemical discharge machining (ECDM) process by use of conductive particles in the electrolyte. In conventional ECDM processes the generation of fine sparks with uniform energy has been most desired technique to improve the machining efficiency and the surface quality. However, precise control of the spark generations in ECDM process has been a challenging problem. In electrical discharge machining (EDM) processes, which is thermal erosion machining process using spark energy similar to the ECDM, powder-mixed EDM (PM-EDM) fluids have been used to improve machining quality. Although the exact role of the conductive particles in the EDM process could not be clearly explained yet, it has been reported that the powder stabilizes discharge current as a result of discharge energy dispersion. Considering the similarity of the ECDM process compared to EDM where electrical sparks are utilized, powder-mixed electrolyte was introduced to create similar effects. In this paper fine graphite powder (which has good thermal and electrical conductivity) mixed with electrolyte has been applied to the ECDM process. Borosilicate glass, which is frequently used as a material for micro structures, was used as a workpiece. To investigate effectiveness of the proposed method experiments were conducted. The experiment results demonstrated that the breakdown voltage was reduced and the peak current during the process was decreased by ten percents. Discharging pattern was modified such that a single discharge pulse was branched into two or three. As a result, the surface quality was improved compared to that from the conventional process. Various experiment results of product quality with respect to powders volume ratio are also presented.