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Electrochemical-machiningfor stress free, smooth surfaces.SOLUTIONS with Effective, Practical Advice
Electrochemical-machining (ECM) is a method of metal removal by controlled electrochemical dissolution of a workpiece. The part to be machined is connected to the positive terminal (anode) of a direct current source. Both the workpiece and the tool, linked to the negative terminal (cathode) are immersed in an electrolyte, thus completing the electrolytic cell. Metal removal occurs in the workpiece upon passage of electrical current in the circuit and reproduces in reverse the tool shape. Thus that a bulge in the tool makes a cavity in the piece and vice versa a cavity in the tool makes a bulge in the piece. Originally developed to shape hard metal, to avoid the need for harder tools, the process has been later employed to shape difficult to machine alloys even if not so hard. Electrochemical machining is normally used for mass production as the process can be adapted to automatic operation with very high metal removal rates. Unlike conventional machining methods, the tool electrode does not wear in the process, and therefore soft metals tools can shape harder workpieces.
Also to drill holes, smooth surfaces and remove fatigue cracks in steel structures. In the aerospace industry it is used to produce aerodynamic surfaces with good surface finish in difficult to machine materials, or to remove excess weight.
ECM displays the advantage of not deforming the surface, avoiding the introduction of surface stresses or of work hardened layers left by chip removal tools. Electrochemical-machining is also effective as a deburring process as it is very fast and much more convenient than the conventional manual method or nontraditional machining processes. As compared to Electrodischarge Machining (EDM), briefly described in our page on Electrical Discharge Cutting, and to laser machining, ECM avoids completely the recast layer, often cause of development of fatigue micro cracks. Electrochemical-machining is called sometimes "reverse electroplating" and can be applied only to metals due to their electrical conductivity. The Electrochemical-machining metal removal tool is advanced along the desired path very close to the work without touching it, decreasing the distance progressively, at a typical rate of 0.02 mm/sec, down to about 0.4 mm. The electrolyte is pumped through the gap so that the products of the electrolysis are forcibly removed. Dimensional accuracy of Electrochemical-machining was poor at the start of development, but in time these problems were overcome. Also the treatment of environmentally polluting waste was finally successfully addressed. For keeping constant operating conditions the electrolyte is filtered and maintained at constant temperature to avoid changes in its conductivity. Smoothing and shaping hard metals by high-rate anodic electrochemical dissolution with simple aqueous electrolyte solutions is currently performed. Electrochemical-machining offers remarkable advantages for cavity-sinking and shaped-hole production operations. Besides direct current, pulsed current sources were recently introduced, claimed to allow better accuracy under proper process control.
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