Electrochemical drilling with vacuum extraction of electrolyte

Forward flow pattern of electrolyte is widely used in electrochemical drilling (ECD) process. But electrolyte in the machining gap presents a sharp divergent flow which causes an abnormal dissolution and even harmful sparking. Reverse flow of electrolyte leads to a stable machining process but is rarely used due to the poor application feasibility. In this paper, an electrochemical drilling method with vacuum extraction of electrolyte has been proposed. Vacuum extraction of electrolyte greatly facilitates the application of reverse flow in electrochemical drilling. Flow distributions along the machining gap with different electrolyte flow pattern are compared numerically and experimentally. Reverse flow using vacuum extraction is shown to improve the process stability while diminishing sparking and formation of striations. Machining characteristics of vacuum extraction are investigated experimentally. To minimize the radial overcut of machined hole by electrochemical machining with vacuum extraction of electrolyte, the orthogonal design is used to optimize process parameters such as initial machining gap, applied voltage, tool feed rate, and electrolyte concentration. Good results have been obtained in the experiments with optimized parameters. (C) 2009 Elsevier B.V. All rights reserved.