1. In friction welding process, materials are joined by _____ motion between materials.
a) rectilinear
b) rubbing
c) translatory
d) brownian
Explanation: Friction welding is a solid-state joining process that produces coalescence in materials, using the heat developed between surfaces through a combination of mechanically induced rubbing motion and applied load. The resulting joint is of forged quality.
2. In arc welding, the voltage on A.C supply system is in the range
1000-1200 V
400-500 V
200-250 V
70-100V
3. All metallic engineering materials which are _____ can be friction welded.
a) soft
b) weldable
c) forgeable
d) metamaterials
Explanation: As a rule, all metallic engineering materials which are forgeable can be friction welded, including automotive valve alloys, maraging steel, tool steel, alloy steels and tantalum. In addition, many castings, powder metals and metal matrix composites are weldable.
4. Friction welding is _____ process.
a) costly
b) cost saving
c) time consuming
d) highly material selective
Explanation: Since dissimilar materials can be joined, a significant cost savings are possible because engineers can design bimetallic parts that use expensive materials only where needed. Expensive forgings and castings can be replaced with less expensive forgings welded to bar stock, tubes, plates and the like.
5. Friction welding produces quality joints, with a 100% _____ weld.
a) lap joint
b) tee-joint
c) butt joint
d) edge joint
Explanation: Friction welding produces forged quality joints, with a 100% butt joint weld through the contact area. Furthermore, in friction welding heat affected zone is much narrower as compared to other welds, which indeed reduces the cost of post-weld heat treatments (stress relieving processes).
6. Which of the following is not true about friction welding?
a) Dissimilar metals cannot be joined
b) This technique is relatively faster as compared to the other techniques
c) This technique is suitable for any parts of shape or size
d) Sheared surfaces can also be joined by the process
Explanation: Following are the few advantages of friction welding over other techniques:
• Dissimilar metals are joined, even some considered incompatible or unweldable.
• The process is at least twice— and up to 100 times—as fast as other welding techniques.
• Friction welders are versatile enough to join a wide range of part shapes, materials and sizes.
• Joint preparation isn’t critical… machined saw cut, and even sheared surfaces are weldable.
7. Which of the following joint have high corrosion resistance?
(a) Welding joint
(b) Riveted joint
(c) Bolted joint
(d) None of the above
8. Which of the following ray is not produced during welding?
(a) Gamma rays
(b) Visible light rays
(c) Infrared ray
(d) Ultra violet rays
9. Which of the following is an example of solid state welding?
(a) Gas welding
(b)Arc welding
(c) Forge welding
(d) Thermit welding
10. The voltage used in resistance welding is generally kept between-
(a) 4-12 volts
(b) 12-20 volts
(c) 20-28 volts
(d) 28-36 volts
11. The heat generated (H) in resistance welding is expressed by-
(a) I2Rt
(b) IR2t
(c) IRt2
(d) 2IRT
12. The voltage needed in resistance welding does not depend upon-
(a) Composition
(b) Area
(c) Thickness of weld
(d) Length of weld
13. Which of the following statement(s) is/are true for resistance welding?
(i)The time for which current flows is very important
(ii)After switching off the current, the pressure is maintained until the weld cools
(iii)Water is circulated through hollow electrodes to cool the electrodes
(a) i & ii
(b) i & iii
(c) ii & iii
(d) i, ii & iii
14.In resistance welding, two electrodes are made of-
(a) Aluminium
(b) Copper
(c) Iron
(d) Bronze
15.Which of the following is not a resistance welding?
(a) Spot welding
(b) Butt welding
(c) Pressure welding
(d) Percussion welding
16.The resistance welding process suitable for welding ferrous and non-ferrous metals upto 8mm thickness is-
(a) Spot welding
(b) Projection welding
(c) Butt welding
(d) Pressure welding
17.In spot welding, for lap joint, the diameter of welded zone (weld nugget) should be-
(a) 4t+2.5mm
(b) 8t+2.5mm
(c) 12t+2.5mm
(d) 2t+2.5mm
Where ‘t’ is thickness of sheet
18.In spot welding, the spacing between two spot welds is-
(a) 4t
(b) 8t
(c) 12t
(d) 16t
19.In spot welding, the tip diameter of electrode is about-
(a) √t
(b) √2t
(c) 2√t
(d) √3t
20.Which resistance welding process is used for making continuous welds between two overlapping pieces of sheet metals?
(a) Projection welding
(b) Seam welding
(c)Flash welding
(d) Percussion welding
21.The current is not passed continuously in-
(a) Projection welding
(b) Seam welding
(c) Flash welding
(d) Percussion welding
22.In which of the following resistance welding process, electrodes of two copper wheels are used-
(a) Projection welding
(b) Seam welding
(c) Flash welding
(d) Percussion welding
23. At what temperature, does fusion welding takes place?
a) 850°C
b) 900°C
c) 950°C
d) 1000°C
Explanation: The process of fusion welding can be used for joining metal to a metal or a metal can be joined to a ceramic. For the joining of this process, a temperature of 900°C is provided for the approach.
24. Which of the following is not a type of diffusion welding?
a) Gas-pressure welding
b) Vacuum fusion welding
c) Eutectic fusion bonding
d) Eutectoid fusion welding
Explanation: Diffusion welding is has three basic techniques which are incorporated by it. These three basic techniques are, gas – pressure welding, vacuum fusion welding and eutectic fusion welding.
25. What is the minimum frequency used in ultrasonic welding?
a) 10,000 Hz
b) 20,000 Hz
c) 30,000 Hz
d) 40,000 Hz
Explanation: The process of ultrasonic welding is mainly used for the joining of similar metals or dissimilar metals using vibration energy, by way of high frequency. The minimum frequency needed for this purpose is 20,000 Hz.
26. What is the maximum frequency used in ultrasonic welding?
a) 30,000 Hz
b) 40,000 Hz
c) 50,000 Hz
d) 60,000 Hz
27. In what conditions are the parts kept before welding in ultrasonic welding method?
a) Low static pressure
b) High static pressure
c) Low moving pressure
d) High moving pressure
Explanation: In ultrasonic welding method, the parts which are to be joined, are kept clamping to one another in between of supporting member and the welding tip. This clamping is done at a low static pressure.
28. What is the maximum thickness that can be welded in ultrasonic welding?
a) 1.8 mm
b) 2.1 mm
c) 2.3 mm
d) 2.5 mm
Explanation: Weldings such as spot welding or continuous seam welding can be done through ultrasonic welding. The maximum thickness that can be achieved varies depending on the metal. The maximum thickness can be that can be welded is 2.5mm.
29. Electric currents are passed is ultrasonic welding.
a) True
b) False
Explanation: In ultrasonic welding method, the parts which are to be joined, are kept clamping to one another in between of supporting member and the welding tip. In doing this, no current is required to be passed through the metal, and usually, no heat is needed for this too.
30. What is the minimum thickness that can be welded in ultrasonic welding?
a) 0.58 mm
b) 0.21 mm
c) 0.38 mm
d) 0.92 mm
31.As the thickness of the part to be welded increases, which of the following parameter for ac welding should also increase?
(a) Voltage
(b) Current
(c) Frequency
(d) All of the above
32. Seam-welding is.........
(a) Multi-spot welding process
(b) Continuous spot welding process
(c) Used to form mesh
(d) Used for welding cylindrical objects
33. Which of the following holds true for friction welding?
a) Hazardous fumes are generated during the process
b) Argon is used as a shielding gas
c) It is a power consuming process
d) There are no solidification defects in the welded parts
34. TIG welding is best suited for welding.......
(a) Stainless steel
(b) Carbon steel
(c) Silver
(d) Aluminium
35. In inertia friction welding ______ energy of welding machine is used.
a) electrical
b) potential
c) rotational
d) frictional
Explanation: Inertia Friction Welding is a variation of friction welding in which the energy required to make the weld is supplied primarily by the stored rotational kinetic energy of the welding machine.
36. In inertia friction welding, one workpiece is connected to _____
a) flywheel
b) the pin tool
c) rotor
d) generator
Explanation: In Inertia Welding, one of the workpieces is connected to a flywheel and the other is restrained from rotating. The flywheel is accelerated to a predetermined rotational speed, storing the required energy. The drive motor is disengaged and workpieces are forced together by the friction welding force.
37. Friction welding process is restricted to_____
a) square bars
b) round bars
c) hexagonal bars
d) bars having diameters less than 20mm
Explanation: The process is restricted to joining round bars of same diameter (or bar tubes to flat surfaces), i.e., capable of being rotated about the axis. Furthermore, capital equipment and tooling costs are high and free-machining alloys are difficult to weld.
38. Which of the following materials cannot be welded by friction welding?
a) Aluminium
b) Copper
c) Stainless steel
d) Non-forgeable materials
39. Which of the following is the effect of increased content of Sulphur and Phosphorous in Steel ?
a) yields high strength
b) affects weldability
c) increases resistance to corrosion
d) improves resistance to high temperature
40. In which of the following areas, friction welded products are not used?
a) Aerospace
b) Automotive
c) Marine
d) Toy making
Explanation: Friction welded parts in production application span over wide products for aerospace, agriculture, automotive, defence, marine and oil industries. Right from tong holds to critical aircraft engine components are friction welded in production.
41. Which of the following automotive components are not friction-welded?
a) Gears
b) Engine valves
c) Strut rods
d) Rims
Explanation: Automotive parts that are friction welded include gears, engine valves, axel tubes, driveline components, strut rods and shock absorbers. Rims are generally welded by TIG or MIG welding
42. In Direct Drive Friction Welding, energy is supplied by _____
a) an electromagnet
b) a capacitor
c) an electric motor
d) a heating unit called heater
Explanation: Direct Drive Friction Welding is a variation of friction welding in which the energy required to make the weld is supplied by the welding machine through a direct motor connection for a preset period of the welding cycle.
43. Which of the following holds true about direct drive friction welding?
a) Both the workpieces are restrained from motion
b) Among two workpieces, the one attached to motor-driven unit is restrained from motion
c) Among two workpieces, the one which is not attached to motor-driven unit is restrained from motion
d) Both the workpieces are moving relative to each other
44. _____ generated during friction welding is coherent.
a) Burr
b) Molten metal
c) Flash curl
d) Fly ash
Explanation: The flash curl generated during welding is coherent, will not flake off, and can often be left intact if design and engineering considerations allow. Alternately, parts can frequently be designed to accommodate the flash curl in a recess (flash trap).
45. Part geometry and accessibility of the flash are the factors which decide flash removal process.
a) True
b) False
46. On which of the following factor, does weldability not depend?
a) Boiling point
b) Melting point
c) Thermal expansion
d) Thermal conductivity
47. How many flash removal systems are there?
a) 2
b) 3
c) 4
d) 5
Explanation: Available systems are:
• Shearing–outside
• Shearing–inside
• Plunge Cut–one axis
• Plunge Cut–two axis.
48. Which of the following components of an aircraft is/are not friction welded?
a) Gears
b) Hooks bolt
c) Shafts
d) Hydraulic cylinders
Explanation: Aircraft/ aerospace components which are friction welded include compressor rotors, fan shafts, cluster gears, landing gear components, bi-metallic rivets and hook bolts, aluminium heat pipes, and cryogenic rocket components.
49. Friction welding is one of the leading methods of joining different metals.
a) True
b) False
Explanation: Proven reliability of friction welded connections, coupled with the process advantages such as being clean, fast, consistent, and free of operator-induced error, makes friction welding one of the leading methods of joining flanges to valve bodies, drill pipe, high-pressure hose couplings, and manifold tubes.
50. Friction welding produces a _____ bond.
a) metallic
b) metallurgical
c) ionic
d) co-ordinate
Explanation: Friction welding produces a metallurgical bond strong enough to take the high torque and highly loaded rotary tension due to directional drilling.
51. Which of the following is not the advantage of friction welding?
a) No smoke generation during the process
b) Less sparks are produced during the process
c) Applicable for all metals
d) Time saving process
Explanation: The advantages of this process such as no smoke, fumes or gases, or few sparks produced, and the fact that the process is machine-controlled, make it suitable for use in potentially explosive or hazardous environments. The machine can be fully automated so the operator can be safely located out of harm’s way. This process is not applicable to non-forgeable metals.
52. Which of the following set is not joined by friction welding process?
a) Aluminium to Steel
b) Copper to Aluminium
c) Copper to Titanium
d) Rubidium to Caesium
Explanation: Metal combinations not normally considered compatible are joined by friction welding, such as aluminium to steel, copper to aluminium, titanium to copper, and nickel alloys to steel.
53. Laser beam welding is a ______ joining process.
a) fission
b) fusion
c) coherent
d) plastic
Explanation: Laser is an acronym for light amplification by stimulated emission of radiation. Laser Beam Welding (LBW) is a fusion joining process that produces coalescence of materials with the heat obtained from a concentrated beam of coherent, monochromatic light impinging on the joint to be welded.
54. Which of the following is used to direct laser beam?
a) glass apertures
b) perforated glass sheets
c) flat optical elements
d) electro-magnetic coils
Explanation: In the LBM process, the laser beam is directed by flat optical elements, such as mirrors and then focused to a small spot (for high power density) at the workpiece using either reflective focusing elements or lenses.
55. Inert gas shielding is generally employed to protect _____
a) laser beam
b) molten puddle of metal
c) filler electrode
d) lenses
Explanation: It is a non-contact process, requiring no pressure to be applied. Inert gas shielding is generally employed to prevent oxidation of the molten puddle and filler metals may be occasionally used.
56. Which of the following is a commercially used laser?
a) Nd-GAG laser
b) 1.06 µm wavelength CO2 laser
c) 2 µm wavelength CO2 laser
d) Nd- YAS laser
Explanation: The Lasers which are predominantly being used for industrial material processing and welding tasks are the Nd-YAG laser and 1.06 µm wavelength CO2 laser, with the active elements most commonly employed in these two varieties of lasers being the neodymium (Nd) ion and the CO2 molecules respectively.
57. In solid state laser _____ is used as a dopant.
a) actinium ion
b) neodymium ion
c) platinum ion
d) lead ion
Explanation: It utilizes an impurity in a host material as the active medium. Thus, the neodymium ion (Nd+++) is used as a ‘dopant’, or purposely added impurity in either a glass or YAG crystal and the 1.06 µm output wavelength is dictated by the neodymium ion.
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58. The lasing material is a cylinder of a diameter of about _____ mm.
a) 5
b) 9
c) 17
d) 20
Explanation: The lasing material or the host is in the form of a cylinder of about 150 mm long and 9 mm in diameter. Both ends of the cylinder are made flat and parallel to each other.
59. The lasing material or crystal is excited by _____
a) neon lamps
b) krypton lamps
c) tungsten wire laps
d) CFLs
Explanation: Both ends of the cylinder are made flat and parallel to very close tolerances, then polished to a good optical finish and silvered to make a reflective surface. The crystal is excited by means of an intense krypton or xenon lamps.
60. Which of the following laser is the most efficient?
a) CO2 lasers
b) Nd-YAG lasers
c) Ruby lasers
d) Dye lasers
Explanation: The electric discharge style CO2 gas lasers are the most efficient type currently available for high power laser beam material processing. Dye lasers use complex organic dyes like rhodamine 6G.
61. CO2 lasers employs gas mixture of _____
a) nitrogen and helium
b) hydrogen and helium
c) argon and xenon
d) oxygen and nitrogen
Explanation: These lasers employ gas mixtures primarily containing nitrogen and helium along with a small percentage of carbon dioxide, and an electric glow discharge is used to pump this laser medium.
62. Gas heating produced by gas lasers is controlled by _____
a) coolant
b) a blow of cool air
c) adjusting the wavelength of the laser
d) circulating the gas mixture
Explanation: Gas heating produced by gas lasers is controlled by continuously circulating the gas mixture through the optical cavity area and the thus CO2 lasers are usually categorized according to the type of gas flow in the system.
63. How many categorize are there of CO2 lasers?
a) 2
b) 3
c) 4
d) 5
Explanation: CO2 laser are usually categorized according to the type of gas flow in the type of gas flow in the system:
• slow axial
• fast axial
• transverse axial.
64. Slow axial flow gas lasers are simplest of the CO2 lasers.
a) True
b) False
Explanation: They are the simplest of the CO2 lasers. Gas flow in the same direction as the laser resonator’s optical axis and electric excitation field, or gas discharge path. These lasers are capable of generating laser beams with a continuous power rating.
65. Solid axial flow CO2 lasers can generate laser beams with a constant rating of 80 Watts.
a) True
b) False
Explanation: These lasers can generate laser beams with a constant rating of approximately 80 Watts for every meter of discharge length. A folded tube configuration is used for achieving output power levels of 50 to 1000 Watts, maximum.
66. ______ is used to circulate the laser gas in case of fast axial flow gas laser.
a) Compressor
b) Turbo pump
c) Guide vanes
d) Vane pump
Explanation: In the case of the FAF Laser, a roots blower or turbo pump is used to circulate the laser gas at high speed through the discharge region and corresponding heat exchangers.
67. Fast axial flow gas lasers are available between _____ watts power levels.
a) 10-100
b) 50-500
c) 500-6000
d) 6000-7000
Explanation: The fast axial flow lasers with continuous wave (CW) output power levels of between 500 to 6000 watts are available. The fast axial flow lasers have a similar arrangement of components as that of slow axial flow gas laser.
68. In transverse flow type gas lasers, gas is circulated across _____
a) the resonator cavity axis
b) optical axis
c) deflection coils
d) the focusing lens
Explanation: These lasers operate by continuously circulating gas across the resonator cavity axis by means of a high speed fan type blower while maintaining an electric discharge perpendicular to both the gas flow direction and the laser beam’s optical axis. Transverse flow lasers with output power levels between 1 and 25 kW are available.
69. In case of laser welding, heat input is _____ to fuse the weld metal.
a) equal to the required amount
b) close to the minimum required
c) greater by 200 J than required
d) approximately higher by atleast 320 J
Explanation: Following are the few advantages of Laser Beam Welding:
• Heat input is close to the minimum required to fuse the weld metal
• Reduced heat affected zones
• Workpiece distortions are minimized due to smaller heat affected zones.
70. Which of the following holds true about laser welding process?
a) Time for welding thick sections is more in case of LBW
b) Shielding gas is used to melt the burr formed during the machining
c) In LBW, sometimes filler metals are used
d) In Nd- YAG lasers, crystals of C14 are used as the lasing material
Explanation: Time for welding thick sections is reduced and the need for filler wires and elaborate joint preparations is eliminated by employing the single pass laser welding procedures but filler metals may be occasionally used.
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71. Laser welding is performed with freedom from electrode contamination.
a) True
b) False
Explanation: In laser beam welding, no electrodes are required.
72. Which of the following does not hold true about laser beam welding?
a) Laser welding cannot be used in case of joints at intricate locations
b) It can produce tiny welds
c) Laser welding can be used for a variety of metal combinations
d) In case of LBW, thin welds on small diameter wires are less susceptible to burn back
Explanation: Following are the advantages of laser beam welding:
• Welding in areas that are not easily accessible with other means of welding can be done by LBM, since the beams can be focused, aligned and directed by optical elements
• Laser beam can be focused on a small area, permitting the joining of small, closely spaced components with tiny welds
• Wide variety of materials including various combinations can be welded
• Thin welds on small diameter wires are less susceptible to burn back than is the case with arc welding.
73. Laser welds are not influenced by _____
a) electric field
b) magnetic field
c) radio waves
d) ultraviolet rays
Explanation: Laser welds are not influenced by magnetic fields, as in arc and electron beam welds. They also tend to follow weld joint through to the root of the work-piece, even when the beam and joint are not perfectly aligned.
74. Aspect ratios, i.e., depth-to-width ratios of the order of _____ are attainable by LBW.
a) 1:2
b) 5:10
c) 10:1
d) 15:1
Explanation: Following are the few advantages of the LBW process:
• Aspect ratios (i.e., depth-to-width ratios) of the order of 10:1 are attainable in LBM
• Metals with dissimilar physical properties, such as electric resistance can also be welded
• No vacuum or X-Ray shielding is required.
75. Weld penetrations of larger than _____ are difficult to weld by LBW.
a) 5 mm
b) 13 mm
c) 19 mm
d) 25 mm
Explanation: The maximum joint thickness that can be welded by a laser beam is somewhat limited. Thus weld penetrations of larger than 19 mms are difficult to weld. Also, joints must be accurately positioned laterally under the beam and at a controlled position with respect to the beam focal point.
76. Which of the following material properties has no effect on laser beam machining?
a) Reflectivity
b) Thermal conductivity
c) Weldability
d) Electrical conductivity
Explanation: High reflectivity and high thermal conductivity of materials like Al and Cu alloys can affect the weldability with lasers. Also, in case of mechanical clamping of the weld joints, it must be ensured that the final position of the joint is accurately aligned with the beam impingement point.
77. Lasers tend to have fairly low energy conversion efficiency.
a) True
b) False
78. Which of the following material properties should match before joining to components by a transmission welding method.
a) Electrical properties
b) Thermal properties
c) Weldability
d) Tensile strength
Explanation: In transmission welding process, the energy is absorbed through novel interfacial absorption methods. Composites can be joined by this process provided that the thermal properties of the matrix and reinforcement are similar.
79. Transmission welding mode is used for materials that______
a) transmits near infrared radiation
b) have high heat capacities
c) have lower melting points
d) absorbs infrared radiations
Explanation: The energy transmission mode of conduction welding is used with materials that transmit near infrared radiation, notably polymer. Absorption of infrared radiation has nothing to do with weldability of materials.
80. In transmission welding mode, absorbing ink is placed at the interface of a lap joint for _____
a) absorbing the laser beam energy
b) cooling the work metal
c) protecting the weld puddle
d) reducing the process time
Explanation: An absorbing ink is placed at the interface of a lap joint. The ink absorbs the laser beam energy, which is conducted into a limited thickness of surrounding material to form a molten interfacial film that solidifies as the welded joint.
81. Butt welds can be made using transmission mode of conduction welding by _____
a) melting the outer surfaced of the joint
b) directing the energy towards the joint
c) applying ink to the joining surface before welding
d) using filler material
Explanation: Butt welds can be made by directing the energy towards the joint line at an angle through material at one side of the joint, or from one end if the material is highly transmissive. Also, thick section lap joints can be made without melting the outer surfaces of the joint.
82. In which of the following processes, the laser beam is used to melt a filler addition?
a) Laser drilling
b) Laser cutting
c) Laser welding
d) Laser soldering
Explanation: In the laser soldering and brazing processes, the beam is used to melt a filler addition, which wets the edges of the joint without melting the base material.
83. In electron beam machine, just after the cathode, there is/are _____
a) deflector coils
b) a magnetic lens
c) bias grid
d) port for vacuum gauge
Explanation: Just after the cathode, there is an annular bias grid. A high negative bias is applied to this grid so that the electrons generated by this cathode do not diverge and approach the next element, the annular anode, in the form of a beam.
84. Electron is accelerated by _____
a) cathode cartridge
b) electromagnetic coils
c) aperture
d) annular anode
Explanation: The annular anode now attracts the electron beam and gradually gets accelerated. As they leave the anode section, the electrons may achieve a velocity as high as half the velocity of light.
85. _____ determines the mode of an electron beam.
a) Applied voltage
b) Operating pressure
c) Position of magnetic lens
d) The nature of biasing
Explanation: The nature of biasing just after the cathode controls the flow of electrons and the biased grid is used as a switch to operate the electron beam gun in pulsed mode.
86. After the anode, the electron beam passes through _____
a) cathode cartridge
b) deflector coils
c) bias grid
d) a series of lenses
Explanation: After the anode, the electron beam passes through a series of magnetic lenses and apertures. The magnetic lenses shape the beam and try to reduce the divergence.
87. In the electron beam gun, apertures ______
a) allow only convergent electrons to pass
b) absorb convergent electrons
c) allow divergent electrons to pass
d) accelerate the electron beam
Explanation: The magnetic lenses shape the beam and try to reduce the divergence. Apertures on the other hand allow only the convergent electrons to pass and capture the divergent low energy electrons from the fringes. This way, the aperture and the magnetic lenses improve the quality of the electron beam.
88. In the final section of the electron beam gun, electron beam passes through the electromagnetic lens and deflection coil.
a) True
b) False
Explanation: After the apertures, the electron beam passes through the final section of the electromagnetic lens and deflection coil. The electromagnetic lens focuses the electron beam to the desired spot. The deflection coil can manoeuvre the electron beam, though by small amount, to improve the shape of the machined holes.
89. What is the purpose of a series of slotted rotating discs provided between the electron beam gun and the workpiece?
a) It increases the accuracy of the beam
b) It can increase the intensity of the beam (if needed)
c) It prevents power losses
d) It prevents vapour generated during machining to reach the gun
Explanation: Generally in between the electron beam gun and the workpiece, which is also under vacuum, there would be a series of slotted rotating discs. Such discs allow the electron beam to pass and machine materials but helpfully prevent metal fumes and vapour generated during machining to reach the gun. Thus it is essential to synchronize the motion of the rotating disc and pulsing of the electron beam gun.
90. For alignment of the beam, _____ is provided.
a) a lens
b) a telescope
c) magnifier
d) microscope
Explanation: Electron beam guns are also provided with illumination facility and a telescope for alignment of the beam with the workpiece. Lens are provided to focus the beam.
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