By electrochemical machining

Metal objects with complex shapes can be formed by electrochemical machining (electroerosion), especially important when mechanical machining is not possible. The object is the anode, where dissolution occurs, and the tool is the cathode, having the form of a mould for the object. The cathode has small holes from which jets of electrolyte exit so that there is a layer of electrolyte between anode and cathode (Fig. 15.9). An extremely important example is the manufacture of components such as blades for turbines. 

B. Ghoshal, B. Bhattacharyya, Influence of vibration on micro-tool fabrication by electrochemical machining, Int. J. Mach. Tools Manuf 64 (2013) 49-59. 

Figure 8.5 Components manufactured by electrochemical machining (a) turbine discs (the cathode tools to form the complex features are also shown), (b) turbine blade with longitudinal cooling holes formed by machining (the holes are seen on the X-ray of the blade and (c) angled square holes for air cooling. Photographs supplied by Rolls Royce Ltd, Aero Division.

This may be why cells use electric signals because these are in principle highly efficient. Electrochemical machines (i.e., storage batteries) are just the type that enable large concentration gradients to be balanced by electrical potential jumps so as to preserve the continuity of the electrochemical potential, which is the requirement for reversibility. The concentration gradients of K+ and Na across cell membranes that... 

Finally, metal objects can sometimes be fabricated in their entirety by electrodeposition (electroforming), with much the same considerations as electroplating. Conversely, portions of a metal specimen can be selectively electrolyzed away (electrochemical machining). This technique is especially useful where the metal to be shaped is too hard or the shape to be cut is too difficult for conventional machining. The sample is made the anode, a specially shaped tool the cathode, and electrolyte solution (e.g., aqueous NaCl) is fed rapidly but uniformly over the surface to be machined. Current densities may reach several hundred amperes per square centimeter across the electrolyte gap of a millimeter or so. Excellent tolerances can be achieved in favorable circumstances.16... 

Hypodermic needles formed by ECM [MACHINING METHODS, ELECTROCHEMICAL] (Vol 15)... 

Electrodeposition and electrodissolution of metals has an important role in the fabrication of metal articles with shapes that are difficult to make by conventional methods32, We exemplify with two types of processing electroformation and electrochemical machining. 

Electrochemical Part-by-Part Machining of Nano- and Microstructures... 

ELECTROCHEMICAL PART-BY-PART MACHINING OF NANO- AND MICROSTRUCTURES... 

Electrochemical machining (ECM) is a method of metal machining that aims at producing parts of specified shape, dimensions, and surface finish. The process is based on the removal of metal by electrochemical dissolution ([1-15] and references cited therein). Special machines have been developed to realize this aim. A complete ECM installation (Fig. 1) consists of the machine, the power supply, the electrolyte circulation system (tank, pump, heat exchanger, and sludge removal unit), and the control system (control of current, voltage, feed rate, gap width, and electrolyte temperature, pH value, pressure, and concentration short-circuit protection). 

Since the mid-1970s there has been a considerable amount of material published on the influence of ultrasound upon the electrochemistry of metal systems. Most of this work was carried out in former Eastern block countries and concentrated on such electrochemical processes as corrosion, electrodeposition, and electrochemical dissolution. Recently there has been an upsurge in the interest shown in sonoelectrochemical processes using both non-metal and metal systems worldwide. There have been a considerable number of publications in the employment of ultrasound in areas as diverse as semiconductor production to sono-electrochemical machining and metal finishing. A review by R. Walker [27] into the use of ultrasound in metal deposition systems, provides an introduction into the fundamental effects of ultrasound in plating and metal finishing. 

Therefore, optimising machining by electrochemical discharges means taking control of the following three aspects ... 

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