Electro Chemical Grinding (ECG)
Electro chemical grinding is also called electrolytic grinding. Metal is removed from the surface of the work piece by electro chemical action and also by abrasive action of a grinding wheel. 90% of metal is removed by electro chemical action and 10% of metal is removed by the abrasive action of the grinding wheel.
The equipment has a metal bonded grinding wheel. Brass, bronze and copper are bonded with abrasive grains in the grinding wheel. Diamond abrasive is used for grinding tungsten. Aluminium oxide abrasive is used for other metals.
The wheel is held in a horizontal spindle. The spindle is supported on insulated bearings. The work piece is held in a fixture against the grinding wheel. A gap of about 0.01mm is maintained between the wheel and the surface of the work piece. The work piece is connected to the positive terminal of a D.C. supply. The grinding wheel is connected to the negative terminal. 4 to 16V, 300 to 1000 Amps D.C supply is applied. A mixture of sodium chlorite, sodium chlorate or sodium nitrate and water is used as the electrolyte. The electrolytic solution is made to flow between the work piece and the grinding wheel. Electro chemical action takes place. Metal from surface of the work piece is removed in small particles. In addition to this, the rotating grinding wheel also removes metal from the work surface by abrasion. The small particles of metal removed from the work piece are carried away by the electrolyte. The electrolyte is collected in a reservoir. It is filtered and recirculated by a pump. Electrolyte also acts as coolant. The work piece is slowly fed towards the grinding wheel maintaining a constant gap between the work piece and the grinding wheel.
· Used for machining hard materials which are conductive to electricity
· Used for grinding of tungsten carbide tool tips and hard steels.
· Used to grind thin section.
· Cylindrical grinding, form grinding, plunge grinding and surface grinding operations are done using this process.
· Used for machining refractory materials, high strength steels, nickel and cobalt base alloys etc.,
· Very fine finish is obtained
· Suitable for machining very hard materials like carbides. Carbides are difficult to machine by other processes.
· No heat is generated during the process.
· No distortion to the work piece
· No burrs are produced.
· Fast operation
· Thin materials can be ground without deflection as the grinding wheel does not press the work piece.
· Wheel wear is drastically reduced.
· No heat is generated so there is no danger of burning or heat distortion.
· This process can be used to machine only metals which are conductive.
· Sharp corners of the work piece cannot be machined.
· Electrolytic solution is corrosive.
· Initial cost of the equipment is high when equipped with larger power supplies.
· Intricate shapes may not be formed.