What do you know about Electro Chemical Machining?
Electro Chemical Machining is a process that converts the electrical energy into chemical energy. Electro Chemical Machining is based on the principle of electrolysis. The process completely rely on Faraday’s law of electrolysis. In this electro chemical machining process, the tool used will act as cathode and the work piece will act as anode.
During this operation, the work piece is placed stationary and the tool is moved at a constant required rate. A very small gap is provided between the tool and the work piece which allows a small DC current to pass through them. The voltage ranges from 3 volts to 30 volts. At this time of passing the electric current, an electrolyte is fed into the gap. The low voltage enables the current to flow through the electrolyte with positively charged ions attracting the tool and the negatively charged ions attracting the work piece. This flow of ions in the electrolyte causes the electro chemical reaction which results in the removal of metal from the work piece or the tool in the form of sludge. This sludge can be removed from the apparatus and can be removed from the bottom. The area closer to the contact pieces results in very high current due to less resistance. Therefore at this area, the metal removal rate is faster, the process continues and the tool reproduces its shape on the work piece.
According to Faraday’s law, if two electrodes considering anode and cathode, are immersed in an electrolyte and a small DC potential is applied on them, then this causes the metal to get detached from anode surface and that material appears on the cathode. This removed metal apperas as coating on the cathode.
As the gap increases between the cathode and anode, the current flow decreases and as the gap increases between the cathode and anode, the current flow increases. If the current flow increases, the material removal rate will be higher and if the current flow decreases, the material removal rate will be lowered. Electro Chemical Machining process is widely used in electro plating by considering the work piece as cathode and the material can also be removed by considering the work piece as anode. This is also known as Reverse Electro Plating. This is also mostly employed.
Functions of an electrolyte in between anode and cathode-
1. It forms a high electric circuit between the tool and the work piece.
2. It dissipates heat which is generated during the chemical reaction.
3. It carries away the metal particles produced during the machining.
4. It provides favorable conditions for the machining reactions to complete the process.
Properties of electrolyte-
1. Electrolyte must posses high electrical conductivity.
2. Electrolyte should posses high Specific Heat.
3. The viscosity must be as low as possible.
4. The electrolyte must be chemically stable.
5. Electrolyte must be chemically active to cause the better metal or material removal rate.
6. Electrolyte should not form any type of excess layer on the top of electrolyte, tool or the work piece.
7. Electrolyte should not be toxic and corrosive.
8. Electrolyte should be economical and easily available.
Advantages of Electro Chemical Machining-
1. Electro Chemical Machining gives high material removal rate designed for high strength and temperature materials.
2. Electro Chemical Machining produces intricate and complex shapes with ease. No hard work is needed.
3. Tool wear is very negligible. We can also consider as no tool wear.
4. Thin metal sheets can be processed very easily.
5. There is an absence of residual stresses and cutting forces on the machined material surface.
6. Electro Chemical Machining produces very close tolerances of about +0.005 mm to -0.005 mm.
7. Electro Chemical Machining can perform the following machining process efficiently namely drilling, milling, grinding and many others, even the processes done on the lathe machine..
Disadvantages of Electro Chemical Machining-
1. Materials that are poor in conducting electricity cannot be machined even to a small extent.
2. Electro Chemical Machining uses high power for proper working.
3. There is more danger of corrosion and rusting in Electro Chemical Machining.
4. We find most difficulty in designing and fabrication of tools.
5. Electro Chemical Machining is not applicable for machining fine corner radii in the work piece.
6. Specially designed and approved fixtures are necessary for Electro Chemical Machining.
7. Required floor area for the placement of the Electro Chemical Machining equipment is large and high.
Applications of Electro Chemical Machining-
1. Machining of hard and heat resistant materials.
2. Machining of cavities in forging dies, for drilling deeper holes and irregular shaped holes.
3. Machining of complex profiles like turbine wheels, turbine and jet blades.
4. Rough corners or edges can be turned into very smooth parts and the process is known as deburring. This can be processed using Electro Chemical Machining.