Manufacture - Electro-chemical

ELECTRO-CHEMICAL MACHINING (E.C.M.)

Fig. 22-11 Electro-chemical machining.

30. This type of machining employs both electrical and chemical effects in the removal of metal. Chemical forming, electro-chemical drilling and elec- trolytic grinding are techniques of electro-chemical machining employed in the production of gas turbine engine components.

31. The principle of the process is that when a current flows between the electrodes immersed in a solution of salts, chemical reactions occur in which metallic ions are transported from one electrode to another (fig. 22-11). Faraday's law of electrolysis explains that the amount of chemical reaction produced by a current is proportional to the quantityof electricity passed.
32. In chemical forming, (fig. 22-11), the tool electrode (the cathode) and the workpiece (the anode) are connected into a direct current circuit. Electrolytic solution passes, under pressure, through the tool electrode and metal is removed from the work gap by electrolytic action. A hydraulic ram advances the tool electrodes into the workpiece to form the desired passage.