Electro-chemical machining

Abstract

The metal and alloys which are difficult to machine by machining process for this purpose electro machining process is used. It has got vide applications in various processes. Its is based on Michall Faradays classical laws of electrolysis requiring basically two electrodes, an electrolyte, a gap and a source of D.C power of sufficient capacity. In the actual process, the cathode is tool-shaped, more or lens like the mirror image of the finished workspace. The work piece is connected to positive supply. The tool or cathode is connected to negative terminal supply. The cathode is advanced towards anode through the electrolyte that completes electric circuit between anode and cathode. The metal is then removed from the workpiece through electrical action and cathode tool shape is reproduced on the workpiece. The metal is detached atom by atom from the anode surface and appears in the electrolyte as positive ions. During electrolysis of water, its molecules gain electrons from cathode so that they separate in to free hydrogen gas and hydroxyl ion. As the anode dissolves, negative charged hydroxyl ions are electrically balanced by positive charged metal ions entering in to the electrolyte. This process is normally used for mass production and used for hard materials. The process is reversed then electroplating where material is added but in this process material is removed instead of addition .The turbine blades are manufactured by this process only.