These methods utilize electric, chemical, sound, or ray energy. They supplement cutting but sometimes can replace it. Electrical discharge machine Electrical discharge machining: 1 – tool (cathode); 2 – pool; 3 – work-piece (anode); 4 – dielectric liquid (kerosene); 5 – insulator ELECTRO-PHYSICAL AND ELECTRO-CHEMICAL PROCESSING Electrical discharge machining is based on erosion (destruction) of electrodes by electric current discharges generated between them. When voltage between electrodes reaches the breakdown value, a spark discharge is generated and elementary volume of metal on the anode is melted and evaporated thus forming a micro crater. Pulled out parts of the metal may solidify in a dielectric liquid forming granules of a micron size. The distance between electrodes is supported automatically at 0.01–0.05 mm.

Schemes of electrical discharge machining a – broaching; b – machining of shaped die cavity; c – broaching a hole with a curved axis; d – grinding internal surface of a die hole; 1 – pulse generator; 2 – dielectric liquid delivery; 3 – tool; 4 – kerosene; 5 - dielectric liquid tapping; 6 – work-piece; 7 – insulator a b cd

Electrospark gear cutting with internal toothing Advantages of electrical discharge machining : 1) absence of force action raises accuracy of processing; 2) the surface of a part is not strengthened; 3) it is easy to automate processes; 4) it is possible to process all necessary surfaces simultaneously; 5) processing goes continuously.

Examples of parts made by electrical discharge machining This method allows making holes and cavities, cut out work-pieces of a complicated shape. It is applied for hard-processed metals and alloys, for example, tool alloys, heat resisting steels.

View A magnified Scheme of electrochemical polishing: 1 – pool; 2 – work-piece; 3 – pole plate; 4 – electrolyte; 5 – micro irregularity; 6 – products of anodic dissolution Parts after electrochemical polishing Electrochemical processing is based on the phenomenon of anodic dissolution. Metal from the anode surface transfers into a chemical compound and dissolves; micro irregularities are dissolved first of all since current density is higher on them.