SECTION-5 (Q/A)

1. State the working principle of EBM?

When the high velocity beam of electrons strike the workpiece, its kinetic energy is converted into heat. This concentrated heat raises the temperature of work material and vaporizes a small amount of it, resulting in removal of metal from the work piece.

2. List any two advantages of EBM?

a.  Very small holes can be machined in any type of material to high accuracy.

b. It is a quicker process. Harder materials can also be machined at a faster rate than conventional machining.

3. What are the limitations of EBM?

a.  The metal removal rate is very slow.

b. It is not suitable for large work pieces. c.  Cost of equipment is very high

d. A little taper produced on hole.

e.  It is applicable only for thin materials.

4. State the principle of LBM?

In laser beam machining process, laser beam is focused on the workpiece by means of lens to give extremely high energy density to melt and vapourise the work material.

5. Give the examples of solid state laser?

a.  Ruby laser.

b. Neodymium doped Yitrium – aluminium – Garnet (YAG) laser. c.  Neodymium – doped glass laser (Nd-glass).

6. What are basic requirements of laser welding?

a.  The focus of the beam should be adjusted to the thickness or the materi al.

b. The wave length of the laser beam must be compatible with the materials being welded.

7. List any two advantages of LBM?

a.  Machining of any materials including non-metal is possible. b. Micro – sized holes can be machined.

c.  Heat affected zone is small around the machined surface.

8. List the limitations of LBM?

a.  High skilled operators are needed. b. Rate of production is high.

c.  Initial investment is high. d. Life of flash lamp is short.

9. What are the applications of LBM?

a.  It is used for making very small holes, difficult welding of non- conductive and refractory materials, cutting complex profiles in thin and hard materials.

b. It can be used for mass micro – machining production.

c.  It can also be used for selective heat treating of materials.

10. State the working principle of PAM?

In plasma are machining process, material is removed by directing a high velocity jet of high temperature (11,000˚C to 28,000˚C ) ionized gas on the workpiece. The high temperature plasma jet melts the material of the workpiece.

11. What are the gases used in PAM?

The commonly used gases are nitrogen, hydrogen, air, mixture or nitrogen –

hydrogen and argon – hydrogen etc.,

12. What are the types of plasma arc torches?

There are two types of plasma are torches. They are :

a.  Direct arc plasma torches (or) Transferred are type.

b. Indirect arc plasma torches (or) Non- transferred are type.

13. What is transferred arc type plasma?

In transferred are type process, electrode is connected to the negative terminal of the D.C power supply and workpiece is connected to the positive terminal of a D.C power supply, so, more electrical energy is transferred to the work, thus giving more heat to the work.

14. What is non – transferred arc type plasma?

In non- transferred are type, electrode is connected to the negative terminal of a D.C. power supply and nozzle is connected to the positive terminal of a D.C. power supply. When the working gas passing through the nozzle, a part of the working gas becomes heated, ionized and emerges from the torch as the plasma jet. This plasma feeds the heat to the workpiece. This type of torches is used for non- conducting materials.

15. Write any two applications of PAM?

a.  It is used for cutting alloy steels, stainless steel, cast  iron, copper, nickel , titanium. Aluminium and alloy of copper and nickel, etc.,

b. It is used for profile cutting