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Normally water soluble NaCl and NaNO 3 are used as electrolyte. The workpiece is made anode Electrolyte is pumped between workpiece and the tool Water is used as base of electrolyte in ECM. Whole process is carried out in a tank, (made of transparent plastic non-reactive to the electrolyte.) The tank is filled with electrolyte. The cavity machined is the mirror image of the tool. This works on the basis of the Faraday’s law of electrolysis. This works on the principle of reverse of electroplating.
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Both electrodes are immersed into the electrolyte solution. Tool is made cathode and kept in close proximity to the workpiece and current is passed through the circuit. The workpiece is made anode of the setup and material is removed by anodic dissolution. Electrochemical machining removes material of electrically conductor workpiece. It is thus seen that Electrochemical machining (ECM) process uses electrical energy in combination with chemical energy to remove the material of workpiece. Material removal rate is of the order of 1600 mm 3/ min for each 1000 amp. represents a major art of the cost of ECM machine. The electrical generating equipment generating electric supply at about 5-15 volt. The only drawback of the process is that huge amount of energy is consumed (about 100 times that required for turning or milling steel). Due to low temperature developed at the time of normal machining of workpiece, no thermal damage is done to the workpiece structure. The chemical composition and structure, melting point, hardness, toughness or brittleness of the material to be machined have no influence on the machining process. Current density in the gap between tool and workpiece is of the order of 0.4 to 8 A per mm 2.īy this process any metal or alloy which is good conductor of electricity can be given any complicated profile in a single step operation. The positive metallic ions will react with negative ions present in the electrolytic solution forming metallic hydroxides can other compounds, and thus the metal will be anodically dissoluted with the formation of sludges and precipitates. When sufficient electrical energy (about 6 eV) is available between tool and workpiece, s metallic ion may be pulled out of the workpiece surface. In this process no spark is produced and the temperatures generated are low which do not cause metallurgical changes in the workpiece material. A great deal of hydrogen is evolved at the cathode, and high pressure of electrolyte across the gap helps dissipate the gas, thereby avoiding polarisation. All this calls for rigid machine structure to resist the hydrostatic and hydro- dynamic forces. Velocity of electrolyte flow through the gap between tool and workpiece is of the order of 30-60 m/sec. The metal from the work is removed due to the ion migration towards the tool and the deposition of the ions on the tool is prevented by pumping a strong stream of electrolyte at high pressure upto 14 kg/cm 2. The electrolyte used is generally an aqueous solution of common salt or dilute acid which dissolves the particles.
USING ECM TOOLS FREE
It is essential that the feed drive system to the tool be free from stick-slip under high forces. The work is generally kept stationary and the tool is fed in a linear direction. The metal removal is carried out by maintaining an electrolyte between the work (anode) and tool (cathode) in a very small gap of 0.1 to 0.2 mm between the two by pumping electrolyte through the gap. Examples of application of this process include aircraft engine parts, turbine blades, grinding of carbide tools and dies, gun drilling etc. This process is ideally suited for the production of deep holes and profiled cavities in electrically conducting materials. It is a production process for machining conducting materials and gives the highest chip removal rates with reasonable surface finish on repetitive work.īy this process, even hardest possible material can be machined. This process is thus reverse of electroplating, but the metal removed from the work before being deposited on the tool is pumped in the flowing electrolyte. This process continues like this till the tool has reproduced its shape in the workpiece. Thus the metal is mainly removed in the form of sludge’s and precipitates by electro chemical and chemical reactions occurring in the electrolytic cell.
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Due to electrolysis process at the cathode, hydroxial (-vely charged) ions are released which combine with the metal ions of anode to form insoluble metal hydroxides.