Important Short Questions and Answers: Chemical and Electro Chemical Energy Based Processes

1.  State the principle of chemical machining process?

In chemical machining process, material is removed from the workpiece through a controlled etching or chemical attack of the workpiece material.

2.     Name the etchants used in chemical machining process?

a.     Caustic Soda

b.     Hydrochloric acid

c.      Nitric acid

d.     Iron carbide.

3.     Name some of the maskants used in CHM?

a.     Butyl rubber

b.     Neoprene rubber

c.      Polymers

d.     Polethylene, etc.,

4.     Write the principle of ECM process?

ECM is based on the principle of Faraday’s laws of Electrolysis and reverse electroplating. In this process, the work piece is connected to positive terminal (anode) and the tool is connected to negative terminal (cathode). When the current is passed, the workpiece loses metal and the dissolved metal is carried out by circulating an electrolyte between the work and tool.

5.     What are the requirements of tool materials in ECM process?

a.     It should be conductor of electricity.

b.     It should be chemically inert to the electrolyte.

c.      It should be easily machinable.

6.     What are the factors to be considered while designing the tool.?

a.     Determine the tool shape, so that the desired shape of the job is obtained under existing machining conditions.

b.     Design the tool by considering the electrolyte flow, insulation strength and fixing arrangements.

7.     State the function of electrolyte used in ECM process?

a.     It carries the current between the tool and the work piece.

b.     It cools the cutting zone which becomes hot due to the flow of high current.

c.      It removes products of machining from the cutting zone.

8.     What are essential characteristics of an electrolyte used in ECM process?

a.     It should be good conductor of electricity.

b.     It should have non- corrosive property

c.      It should have low viscosity and high specific heat.

d.     It should be non-toxicity and chemical stability.

9.     What are materials used for tools in Electro chemical Machining?

Most commonly used tool materials are copper, brass, titanium, copper- tungsten and stainless steel when the electrolyte is made of sodium or potassium.

The other materials which can be used as tool materials are aluminum. Graphite, bronze, platinum, tungsten carbide.

10.                        What are the advantages of ECM?

a.     Metal removal rate is high compared to conventional machining process.

b.     Wear and tear of the tool is negligible.

c.      The machined work surface is free of stresses.

d.     No cutting forces are involved in the process.

e.      High surface finish of the order 0.2 to 0.8 microns can be obtained.

11.                        What are the disadvantages of Electro Chemical Machining process?

a.     Non- conducting materials cannot be machined.

b.     Initial investment is quite high.

c.      More space is required.

d.     Consumption of power is high.

12.                        List the applications of ECM process? It is used for

a.     Machining complicated profiles

b.     Drilling small deep holes.

c.      Machining of hard materials and heat resistant materials.

d.     Machining of cavities and holes of irregular shapes.

13.                        What are the limitations of ECM process?

a.     Sharp internal corners cannot be obtained. Tool design is very complicated and it requires cut and try method to achieve the final shape.

b.     Post machining cleaning is needed to reduce the corrosion of the work piece.

14.                        List the advantages of Electro Chemical Grinding (ECG) process/

a.     Tool wear is negligible. So, the life of the grinding wheel is increased.

b.     Good surface finish is obtained.

c.      Burr free and stress free components are produced.

d.     As compared to conventional grinding, a very little cutting force is applied to the work piece.

15.                        List the disadvantages of ECG process?

a.     Initial cost is high.

b.     Power consumption is high.

c.      Metal removal rate is lower than conventional grinding.

d.     Non- conducting materials cannot be machined.

16.                        What is the difference between ECG and conventional grinding?

In conventional grinding process, metal is removed from the workpiece by using grinding wheel.

In electrochemical grinding process, the work is machined by the combined action of electrochemical effect and conventional grinding operation.