MCQ’s On Thermal Processes
1. In advanced machining processes, what is the full form of EDM?
a) Electro discharge Machining
b) Electro discharge Manufacturing
c) Electrical dimensioning Machining
d) Electrode dimensions Manufacturing
Answer & Explanations
Answer: a
Explanation: Full form of EDM in advanced machining processes is, Electrodischarge machining.
2. The evolution of wire EDM took place in which part of history?
a) 1940s
b) 1950s
c) 1960s
d) 1970s
Answer & Explanations
Answer: d
Explanation: Evolution of wire EDM in 1970s was due to powerful generators, new wire electrodes, improved machining intelligence and better flushing.
3. Machining speeds have gone up to how many times after the invention of EDM?
a) Ten
b) Twenty
c) Thirty
d) Fifty
Answer & Explanations
Answer: b
Explanation: Machining speeds have gone up to 20 times after the invention of EDM.
4. By using EDM, how much percentage of machining costs can be reduced?
a) 10 %
b) 20 %
c) 30 %
d) 50 %
Answer & Explanations
Answer: c
Explanation: EDM decreased the machined cost at least by 30 %.
5. After invention of EDM, surface finish have improved by how much factor?
a) 10
b) 15
c) 20
d) 25
Answer & Explanations
Answer: b
Explanation: Surface finish have been improved by a factor of 15 after the invention of EDM.
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6. Cavities with, which of the following factors can be produced using Electro discharge machining?
a) Thin walls
b) Fine features
c) Thin walls & Fine features
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: Cavities with thin walls and fine features can be machined using EDM.
7. Which of the following geometries can be machined using EDM?
a) Simple
b) Complex
c) Difficult to cut
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Electrodischarge machining can be used for simple as well as complex geometries.
8. State whether the following statement is true or false regarding EDM.
“In EDM, process is affected by hardness of material.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: EDM process is not affected by the hardness of material.
9. How much amount of burr is produced in this process?
a) 10 %
b) 40 %
c) 70 %
d) No burr
Answer & Explanations
Answer: d
Explanation: Electro discharge machining is a burr free process.
10. Which of the following mechanisms is used for material removal?
a) Electro discharge erosion
b) Magnetic abrasion
c) Electro chemical dissolution
d) Mechanical erosion
Answer & Explanations
Answer: a
Explanation: Material is removed by electro-discharge erosion (EDE) in EDM.
11. What is the value of order of frequency applied between the two electrodes in EDM?
a) 1 kHz
b) 3 kHz
c) 5 kHz
d) 7 kHz
Answer & Explanations
Answer: c
Explanation: The magnitude of frequency applied between the electrodes in EDM is about 5 kHz.
12. What are the magnitude of voltages used in Electro discharge machining?
a) 1 to 20 V
b) 20 to 120 V
c) 120 to 220 V
d) 220 to 320 V
Answer & Explanations
Answer: b
Explanation: In EDM, the magnitude of voltages range between 20 and 120 V.
13. What are the values of gaps between the electrodes in EDM?
a) 0.001 – 0.05 mm
b) 0.01 – 0.5 mm
c) 0.1 – 5 mm
d) 1 – 15 mm
Answer & Explanations
Answer: b
Explanation: In EDM, very small gaps that range between 0.01 – 0.5 mm are maintained.
14. How is material removed in Electro discharge machining?
a) Melt and evaporate
b) Corrode and break
c) Mechanical erosion takes place
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: In Electro discharge machining, material is melted and then evaporated.
15. What is the radius of channel, when electrical breakdown occur?
a) 4 µm
b) 6 µm
c) 8 µm
d) 10 µm
Answer & Explanations
Answer: d
Explanation: In EDM, the electrical breakdown occurs in dielectric in a channel of radius about 10 µm.
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16. State whether the following statement is true or false regarding EDM.
“In EDM, negative ions (electrons) collide with positive ions to generate heat.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: In Electro discharge machining, electrons collide with neutral atoms producing positive ions and further electrons.
17. What are the values of temperature that are obtained while machining using EDM?
a) 2000 to 3000ᵒC
b) 4000 to 6000ᵒC
c) 8000 to 12000ᵒC
d) 15000 to 20000ᵒC
Answer & Explanations
Answer: c
Explanation: The temperatures obtained when the ions reach their respective electrodes, range between 8000ᵒC and 12000ᵒC.
18. What range of heat fluxes are obtained while machining using EDM?
a) 1017 W/m2
b) 1019 W/m2
c) 1024 W/m2
d) 1027 W/m2
Answer & Explanations
Answer: a
Explanation: Heat flux up to the value of 1017 W/m2 are obtained in EDM.
19. What is the duration of sparks that are produced in Electro discharge machining?
a) 0.001 – 1 µs
b) 0.1 – 2000 µs
c) 0.2 – 100 ms
d) 100 – 2000 ms
Answer & Explanations
Answer: b
Explanation: Duration of spark in Electro discharge machining is about 0.1 to 2000 µs.
20. State whether the following statement is true or false about material removal in EDM.
“In EDM, high pressures allow the metal to evaporate.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: High pressures in EDM try to prevent the super-heated metal from evaporation.
21. What are the values of pressure of the plasma in EDM?
a) Up to 2 atm
b) Up to 20 atm
c) Up to 200 atm
d) Up to 2000 atm
Answer & Explanations
Answer: c
Explanation: Pressure on the plasma channel rises to values as high as 200 atm when dielectric evaporates.
22. At the end of pulse, super-heated metal evaporates _______________
a) Explosively
b) Normally
c) Periodically
d) Occasionally
Answer & Explanations
Answer: a
Explanation: At the end of pulse, pressure drops suddenly and super-heated metal evaporates explosively.
23. After the explosion is over, how is the debris carried away?
a) Evaporation
b) Fresh dielectric
c) Old dielectric
d) All of the mentioned
Answer & Explanations
Answer: b
Explanation: Debris is carried away by the fresh dielectric that rushes in.
24. The layer formed when unexpelled molten metal solidifies is known as _______________
a) Reabsorbed layer
b) Recast layer
c) Unevaporated layer
d) Condensed layer
Answer & Explanations
Answer: b
Explanation: Unexpelled molten metal solidifies to form a layer known as recast layer.
25. Amount of material removed from anode and cathode depend on which of the following?
a) Electrons
b) Positive ions
c) Electrons & Positive ions
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: The amount of material removed from electrodes depend on the contribution of the charged ions.
26. What happens when the electron current predominates in the discharge?
a) More anodic removal
b) More cathodic removal
c) Remains same
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: When electron current predominates the electrical discharge, anodic material removal is greater than cathodic material.
27. Between what values mentioned below, do the discharges and sparks usually vary?
a) 1 and 10,000
b) 500 and 500,000
c) 500,000 and 1,000,000
d) None of the mentioned
Answer & Explanations
Answer: b
Explanation: Frequency of discharges or sparks generally vary between 500 and 500,000 sparks per second.
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28. What is the value of gap maintained between the electrodes when we use servo mechanism?
a) 10 – 100 µm
b) 100 – 200 µm
c) 200 – 500 µm
d) 500 – 1000 µm
Answer & Explanations
Answer: c
Explanation: In EDM, value of gap maintained between the electrodes range between 200 and 500 µm.
29. Based on the electrode gap, which of the following electric pulses are generated?
a) Open Circuit pulses
b) Sparks
c) Arcs
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Based on the electrode gap, electric pulses are distinguished which are – circuit pulses, sparks, arcs and short circuits.
30. State whether the following statement is true or false regarding EDM.
“In Electro discharge machining, electric pulses generated affect the material removal.”
a) True
b) False
Answer & Explanations
Answer: a
Explanation: In Electro discharge machining, electric pulses generated have an impact on the material removal.
31. Open gap voltages contribute to how much amount of material removal?
a) 20 %
b) 50 %
c) 70 %
d) No contribution
Answer & Explanations
Answer: d
Explanation: Open gap voltage that occur at too large distances do not contribute to any material removal.
32. When the electrode gap is too small or electrodes are in contact, how much material is removed?
a) 10%
b) 20%
c) 30%
d) No material removed
Answer & Explanations
Answer: d
Explanation: When electrodes come in contact with one another, short circuits occur and material removed is not possible.
33. Which components mentioned below are affected due to arcs?
a) Work piece
b) Tool
c) Work piece & Tool
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: Arcs are believed to occur at same spots on electrode surfaces which damage both tool and work piece.
34. Which of the following pulses contribute to the desired material removal in EDM?
a) Open circuit pulses
b) Short circuits
c) Arcs
d) Sparks
Answer & Explanations
Answer: d
Explanation: The sparks are the one which contributes to the desired material removal in Electro discharge machining.
35. Which of the following are main components of EDM?
a) Dielectric system
b) Servomechanism
c) Power supply
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Main components of machining system in EDM are – dielectric system, power supply and servomechanism.
36. What is the function of feed-control system in Electro discharge machining?
a) Constant gap
b) Supply power
c) Dielectric fluid supply
d) Work piece holding
Answer & Explanations
Answer: a
Explanation: Feed control system is used to maintain constant gap between electrodes.
37. What is the use of power supply system in Electro discharge machining?
a) Constant gap
b) Supply power
c) Dielectric fluid supply
d) Work piece holding
Answer & Explanations
Answer: b
Explanation: Power supply system is used to supply pulses at certain voltages, current, on time and off time.
38. What is the function of dielectric circulation unit in Electro discharge machining?
a) Constant gap
b) Supply power
c) Dielectric fluid supply
d) Work piece holding
Answer & Explanations
Answer: c
Explanation: Dielectric circulation unit is used to supply dielectric fluid for flushing.
39. Which of the following materials are used as electrodes in EDM?
a) Graphite
b) Copper
c) Brass
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: All the materials mentioned above, can be used as electrodes in Electro discharge machining.
40. Metals with _________ melting point and _________ electrical conductivity are chosen as tools in EDM.
a) Low, good
b) Low, bad
c) High, good
d) High, bad
Answer & Explanations
Answer: c
Explanation: In EDM, metals with high melting point and good electrical conductivity are used as tools.
41. Copper has _________ Electro discharge machining wear and _________ conductivity.
a) Good, better
b) Good, worse
c) Bad, better
d) Bad, worse
Answer & Explanations
Answer: a
Explanation: Cu is the metal which has better conductivity and good electro discharge machining wear.
42. Which of the following tungsten carbides are used as electrodes in EDM?
a) Silver tungsten
b) Copper tungsten
c) All of the mentioned
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: Both Silver tungsten and copper tungsten are the tungsten carbides used in EDM.
43. State whether the following statement is true or false regarding materials used in Electro discharge machining.
“In metals, copper graphite has less electrical conductivity than graphite.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: Copper graphite has better electrical conductivity than graphite.
44. Brass metal ensures which type of sparking conditions in Electro discharge machining?
a) Stable
b) Unstable
c) Unsteady
d) Insecure
Answer & Explanations
Answer: a
Explanation: Brass is a type of metal which ensures stable sparking conditions in Electro discharge machining.
45. In addition to the feed of tool, Electro discharge machining tool can have which type of motion?
a) Oscillatory
b) Rotary
c) Vibrational
d) All of the mentioned
Answer & Explanations
Answer: b
Explanation: In addition to feed, the tool electrode may have rotary or orbiting motion.
46. Which of the following parameters determines the size of cavities?
a) Size of electrode
b) Radius of orbit
c) All of the mentioned
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: Size of electrode and radius of orbit determines the size of cavities in EDM.
47. Electrode orbiting ________ the flushing of dielectric fluid in Electro discharge machining.
a) Improves
b) Decreases
c) Reduces
d) Degrades
Answer & Explanations
Answer: a
Explanation: The additional orbiting motion of electrodes helps in improving the flushing by creating a pumping effect of dielectric liquid.
48. Quality of hole produced by orbiting motion is _________ to that obtained by using stationary electrode.
a) Inferior
b) Superior
c) Lower
d) All of the mentioned
Answer & Explanations
Answer: b
Explanation: Quality of hole produced by orbiting motion is superior to that obtained by using stationary electrode.
49. In EDM, electrode polarity depends up on which of the following components?
a) Work piece
b) Electrode material
c) All of the mentioned
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: In Electro discharge machining, electrode polarity depends on both work piece and electrode material.
50. Which one among the following, is the most important factor in determining the tool wear?
a) Melting point
b) Boiling point
c) Power supplied
d) Feed rate
Answer & Explanations
Answer: a
Explanation: In EDM, melting point is the most important factor in determining the tool wear.
51. Electrode wear ratios can be expressed as, which of the following wears?
a) End wear
b) Side wear
c) Corner wear
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Electrode wear ratios are expressed as end wear, corner wear, side wear and volume wear.
52. The term no wear in EDM occurs when electro-to-work piece wear ratio is __________
a) <1%
b) <3%
c) <5%
d) <10%
Answer & Explanations
Answer: a
Explanation: In Electro discharge machining, no wear is the term used when the electrode-to-work piece ratio is less than 1%.
53. Which of the following are the other factors that influence the electrode wear?
a) Voltage
b) Current
c) Electrode material
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: In EDM, electrode wear depends on the factors such as voltage, current, electrode material and polarity.
54. State whether the following statement is true or false regarding wear in EDM.
“In EDM, electrode wear is less dominant when it comes to micromachining applications.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: Electrode wear is more when it comes to micromachining applications in EDM.
55. State whether the following statement is true or false regarding wear in EDM.
“In EDM, corner wear ratio does not depend on type of electrode material.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: In EDM, corner wear ratio depend on the material of electrode used.
56. In Electro discharge machining, highest wear ratio is associated with which type of melting point?
a) Low
b) Medium
c) High
d) Very high
Answer & Explanations
Answer: a
Explanation: In Electro discharge machining, lowering of the melting point of electrode material results in high wear ratio.
57. Which of the following is not a function of dielectric in EDM?
a) Flush particles
b) Cool the section
c) Maintain voltage
d) Provide insulation
Answer & Explanations
Answer: c
Explanation: Flushing particles, providing insulation and cooling the sections that are heated, are the functions of dielectric.
58. Which of the following are the main requirements of dielectric fluids?
a) Viscosity
b) High flash point
c) Minimum odour
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Adequate viscosity, high flash point, oxidation stability, minimum odour, low cost and good electrical discharge are the main requirements of dielectric fluids.
59. Which of the following can be used as dielectric fluids in EDM?
a) Kerosene
b) Silicon fluids
c) Distilled water
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: The dielectric fluids used are kerosene, silicon fluid, ethylene glycol, water in emulsions and distilled water.
60. In EDM, inadequate flushing will not result in which of the following consequences?
a) Arcing
b) Debris removal
c) Decrease electrode life
d) Increased production time
Answer & Explanations
Answer: b
Explanation: Inadequate flushing in Electro discharge machining results in less removal or no removal of debris.
61. Which methods below, are used for introducing the dielectric in machining gap?
a) Normal flow
b) Reverse flow
c) Jet flushing
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Four methods namely normal flow, reverse flow, jet flushing and immersion flushing are used for introducing dielectric.
62. Few large holes are _________ than many small flushing holes in Electro discharge machining.
a) Worse
b) Better
c) Well
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: Many small holes are better than a few large holes in machining thorough the EDM process.
63. State whether the following statement is true or false regarding the dielectric in EDM.
“In EDM, flushing through the tool is more preferred than side flushing.”
a) True
b) False
Answer & Explanations
Answer: a
Explanation: Flushing through the tool is preferred than side flushing for deep cuts.
64. In Electro discharge machining, which type of dielectric flow mentioned below is desirable?
a) Unsteady flow
b) Steady flow
c) Unstable flow
d) None of the mentioned
Answer & Explanations
Answer: b
Explanation: In EDM, steady dielectric flow on the entire electrode-work piece interfaces is most desirable.
65. Metal is removed on which of the components in electro discharge machining?
a) Electrode tool
b) Work piece
c) Electrode tool & Work piece
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: In Electro discharge machining, material is removed from both tool and work piece.
66. On which of the following components, does the MRR depend?
a) Work piece
b) Electrode tool
c) Electrode tool & Work piece
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: Material removal rate not only depends on work piece material but also the tool material.
67. Which of the following factors influence the material removal rate?
a) Pulse condition
b) Electrode polarity
c) Machining medium
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: The factors such as pulse conditions, electrode polarity and machining medium also affect the material removal rate.
68. In Electro discharge machining, materials with low melting point have which type of material removal rate?
a) Very low
b) Low
c) Medium
d) High
Answer & Explanations
Answer: d
Explanation: In Electro discharge machining, materials having low melting point have high material removal rates and vice-versa.
69. In Electro discharge machining, materials with low melting point have which type of surface roughness?
a) Rough
b) Smooth
c) Fine
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: In Electro discharge machining, materials having low melting point have high rougher surfaces and vice-versa.
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70. What are the values of material removal rates in EDM?
a) 0.001 to 0.1 mm3/min
b) 0.1 to 400 mm3/min
c) 400 to 1000 mm3/min
d) 1000 to 5000 mm3/min
Answer & Explanations
Answer: b
Explanation: In EDM, material removal rates range from 0.10 to 400 mm3/min.
71. What happens to the material removal rate if the sparks are very less in EDM?
a) Decreases
b) Increases
c) Increase and then decrease
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: In EDM, if sparks generated are less then material removal rate decreases.
72. What is the relation between the melting point and the material removal rate?
a) Directly Proportional
b) Inversely proportional
c) Indirectly proportional
d) None of the mentioned
Answer & Explanations
Answer: b
Explanation: In Electro discharge machining, material removal rate is inversely proportional to the melting point.
73. What happens to the crater size if we increase the current keeping the pulse time constant?
a) Increase
b) Decrease
c) Decrease and increase
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: By keeping pulse time constant and increasing current, crater size also increases.
74. What happens to the crater size if we decrease the pulse time keeping the current constant?
a) Increase
b) Decrease
c) Increase and decrease
d) None of the mentioned
Answer & Explanations
Answer: b
Explanation: By decreasing pulse time and keeping current constant, crater size also decreases.
75. On which of the following factors do the craters depend?
a) Physical properties
b) Mechanical properties
c) Composition of medium
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: In EDM, craters depend on the physical and mechanical properties of material and composition of medium.
76. The maximum depth of damaged layer is how many times that of average surface roughness?
a) 1.5 time
b) 2 times
c) 2.5 times
d) 3 times
Answer & Explanations
Answer: c
Explanation: Depth of damaged layer is two and half times the average surface roughness value.
77. What happens to the surface roughness values if the MRR increases in EDM?
a) Increases
b) Decreases
c) Decrease and increase
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: In EDM, the surface roughness values increases linearly with increase in the material removal rates.
78. State whether the following statement is true or false regarding the surface roughness in EDM.
“In EDM, graphite electrodes produce smoother surfaces than metal ones.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: In EDM, graphite electrodes produce rougher surfaces than that of the metal ones.
79. In Electro discharge machining, what happens to the surface finish if the pulse energy is decreased?
a) Reduces
b) Decreases
c) Improves
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: In Electro discharge machining, the surface finish improves if the pulse energy is decreased.
80. Using of a mate electrode in Electro discharge machining _____________ the surface roughness of material.
a) Increases
b) Decreases
c) Enhances
d) None of the mentioned
Answer & Explanations
Answer: b
Explanation: By using a mate electrode in Electro discharge machining, the surface roughness values are decreased.
81. What happens to the surface roughness if oxygen gas is introduced in the gap?
a) Increases
b) Decreases
c) Decrease and then increase
d) All of the mentioned
Answer & Explanations
Answer: b
Explanation: In EDM, surface roughness increases with the supply of oxygen gas in gaps.
82. By how much percent surface roughness is reduced if we use proper dielectric flow?
a) 25%
b) 50%
c) 75%
d) 100%
Answer & Explanations
Answer: b
Explanation: In Electro discharge machining, if we use a proper dielectric fluid flow, surface roughness is decreased by 50 percent.
83. What are the tolerance values obtained by machining using EDM?
a) ± 10 mm
b) ± 15 mm
c) ± 25 mm
d) ± 40 mm
Answer & Explanations
Answer: c
Explanation: The tolerance values of ± 25 mm are obtained when we machine components using EDM.
84. How much extra tolerances are achieved when we choose proper variables?
a) ± 5 mm
b) ± 10 mm
c) ± 15 mm
d) ± 20 mm
Answer & Explanations
Answer: a
Explanation: Extra tolerances of ± 5 mm are obtained with a proper choice of process variables.
85. What are the values of temperatures obtained in Electro discharge machining?
a) 1000 to 2000 oC
b) 2000 to 4000 oC
c) 4000 to 8000 oC
d) 8000 to 12000 oC
Answer & Explanations
Answer: d
Explanation: The temperature attained while machining in Electro discharge machining are from 8000 to 12000 oC.
86. What is the value of thickness of recast layer obtained when power of 5 µJ is given?
a) 1 µm
b) 3 µm
c) 5 µm
d) 7 µm
Answer & Explanations
Answer: a
Explanation: When a power of 5 µJ is given, recast layer thickness of 1 µm is obtained.
87. What are the values of thickness of recast layers in Electro discharge machining?
a) 0.001 to 0.025 µm
b) 0.01 to 0.25 µm
c) 1 to 25 µm
d) 10 to 250 µm
Answer & Explanations
Answer: c
Explanation: In Electro discharge machining, the value of thickness of recast layers ranges from 1 to 25 µm.
88. In Electro discharge machining, some annealing of the work piece can be expected __________ the machined surface.
a) On
b) Just below
c) Above
d) At bottom
Answer & Explanations
Answer: b
Explanation: Annealing of some part of the work piece in EDM can be expected just below the machined surface.
89. The depth of the annealed surface is __________ to the amount of power used in machining operation.
a) Directly proportional
b) Inversely proportional
c) Exponential
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: The depth of annealed surface in EDM is proportional to the amount of power used.
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90. What are the values of thickness of annealed surface obtained while machining using EDM?
a) 1 to 25 µm
b) 50 to 200 µm
c) 200 to 500 µm
d) 500 to 1000 µm
Answer & Explanations
Answer: b
Explanation: Values of annealed surface thickness range from 50 µm to 200 µm.
91. In EDM, choosing electrodes that produce which type of machining reduces the annealing effect?
a) Stable
b) Unstable
c) Uneven
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: In Electro discharge machining, choosing the electrodes which produce more stable machining reduces the annealing effect.
92. What happens to the fatigue strength of alloys if altered surfaces are produced in Electro discharge machining?
a) Increases
b) Reduces
c) Enhances
d) Improves
Answer & Explanations
Answer: b
Explanation: The altered surface layers that are produced in Electro discharge machining, significantly reduces the fatigue strength of alloys.
93. The altered layers formed during the process of EDM consists of which of the following?
a) Tempered layers
b) Heat affected zones
c) Intergranular precipitates
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Altered layers consists of recast layers, tempered layers, HAZs and intergranular precipitates in EDM.
94. During roughing process through Electro discharge machining, what is the thickness of layer formed?
a) <0.075 mm
b) <0.125 mm
c) <0.500 mm
d) <0.750 mm
Answer & Explanations
Answer: b
Explanation: The thickness of layer obtained after machining is <0.127 mm in EDM.
95. During finishing process through Electro discharge machining, what is the value thickness of layer formed?
a) <0.075 mm
b) <0.125 mm
c) <0.500 mm
d) <0.750 mm
Answer & Explanations
Answer: a
Explanation: The thickness of layer obtained during EDM finishing is <0.075 mm.
96. Which of the following processes can be used for restoration of fatigue properties?
a) Low-stress grinding
b) Chemical machining
c) Reheat treatment
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: For removal of altered layers processes such as low-stress grinding, chemical machining, reheat treatment, metallurgical type coating and application of shot peening.
97. State whether the following statement is true or false regarding the HAZ in EDM.
“In EDM, post treatment to recover fatigue strength is not recommended.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: After machining using EDM, post treatment to restore the fatigue strength is recommended.
98. Which of the following shapes can be produced using Electro discharge machining?
a) Complex shapes
b) Simple shapes
c) All of the mentioned
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: Electro discharge machining is used to machine complex shapes to a high degree of accuracy.
99. Which of the following materials can be machined using Electro discharge machining?
a) Heat resistant alloys
b) Super alloys
c) Carbides
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: EDM is used to machine materials such as carbides, heat resistant and super alloys which are difficult-to-machine materials.
100. Which of the following are the applications of Electro discharge machining?
a) Holes
b) Slots
c) Texturing
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Micromachining of holes, slots, dies, texturing, milling, surface modification and mechanical pulsing are some typical applications of Electro discharge machining.
101. State whether the following statement is true or false regarding the applications of EDM.
“In advanced machining processes, the incorporation of EDM with CIM increased the length of time for unit operation.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: The incorporation of EDM in CIM reduced the length of time per unit operation.
102. Which type of electrode is used for drilling in Electro discharge machining?
a) Flat electrode
b) Cuboidal electrode
c) Tubular electrode
d) Spherical electrode
Answer & Explanations
Answer: c
Explanation: Tubular electrode is mostly preferred in Electro discharge machining, for drilling purpose.
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103. The dielectric fluid is flushed in thorough which part of the electrode in drilling in EDM?
a) Interior hole
b) Side gaps
c) All of the mentioned
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: EDM drilling uses a tubular electrode which flushes the dielectric thorough the interior holes for removing debris.
104. Which type of holes can be produced through drilling using Electro discharge machining?
a) Irregular
b) Curved
c) Tapered
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Drilling of work piece using EDM produced holes which can be irregular, curved, tapered as well as inclined holes.
105. What are the values of general feed rates used for drilling in EDM?
a) 0.1 mm/min
b) 0.3 m/min
c) 0.5 mm/min
d) 0.7 mm/min
Answer & Explanations
Answer: a
Explanation: Usually a feed rate of 0.10 mm/min is used for drilling the work piece using Electro discharge machining.
106. What are range of diameter values obtained by drilling using EDM?
a) 0.01 to 0.05 mm
b) 0.1 to 0.5 mm
c) 1 to 5 mm
d) 10 to 15 mm
Answer & Explanations
Answer: b
Explanation: Diameter values while drilled using Electro discharge machining, ranges from 0.10 to 0.50 mm.
107. What are the values of overcuts left behind after drilling of work piece?
a) 0.01 to 0.05 mm
b) 0.1 to 0.5 mm
c) 1 to 5 mm
d) 10 to 15 mm
Answer & Explanations
Answer: a
Explanation: Overcut values from 0.01 to 0.05 mm are obtained after the drilling process in EDM.
108. Electro discharge sawing is an application of EDM which employs __________ as tool material.
a) Steel band
b) Disc
c) Steel band & Disc
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: Electro discharge sawing is an application of EDM which employs either steel band or disc as tool.
109. When compared to the conventional abrasive sawing, how many times faster is the MRR?
a) Twice
b) Thrice
c) Four
d) Five
Answer & Explanations
Answer: a
Explanation: Electro discharge sawing cuts the work piece material at the rates which are twice that of conventional abrasive sawing method.
110. How much amount of burr is produce while machined using Electro discharge sawing?
a) 10%
b) 20%
c) 50%
d) No Burr
Answer & Explanations
Answer: d
Explanation: The cuts produced in Electro discharge sawing have smaller kerf widths which hav no burrs in it.
111. What are the values of finish obtained by machining work piece thorough Electro discharge sawing?
a) 0.1 to 4 µm
b) 6.3 to 10 µm
c) 12.4 to 23 µm
d) 25.6 to 40 µm
Answer & Explanations
Answer: b
Explanation: The finish obtained ranges from 6.3 to 10 µm when machined using Electro discharge sawing.
112. What are the recast layer thickness values obtained in ED sawing?
a) 0.001 to 0.022 mm
b) 0.025 to 0.130 mm
c) 0.236 to 0.352 mm
d) 0.432 to 0.568 mm
Answer & Explanations
Answer: b
Explanation: The recast layer thickness values obtained from ED sawing range from 0.025 to 0.13 mm.
113. Which of the following electrodes are used for machining spherical surfaces in Electro discharge machining?
a) Tubular electrodes
b) Flat electrodes
c) Cuboidal electrodes
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: Simple tubular electrodes are used to machine convex and concave spherical surfaces.
114. What are the values of dimensional accuracy obtained while machining spherical surfaces?
a) ± 1 µm
b) ± 3 µm
c) ± 5 µm
d) ± 7 µm
Answer & Explanations
Answer: a
Explanation: Dimensional accuracy of ± 1 µm is obtained while machining spherical surfaces using EDM.
115. What are the surface roughness values obtained while machining spherical surfaces using Electro discharge machining?
a) <0.1 µm
b) <0.3 µm
c) <0.5 µm
d) <0.7 µm
Answer & Explanations
Answer: a
Explanation: The surface roughness values obtained while machining of spherical surfaces are <0.1 µm in Electro discharge machining.
116. Which motion of tool is used for machining spherical surfaces in Electro discharge machining?
a) Oscillatory
b) Vibratory
c) Rotary
d) All of the mentioned
Answer & Explanations
Answer: c
Explanation: The rotary motion tool is used for machining spherical surfaces of conducting ceramic materials in EDM.
117. Which type of electrodes are used for milling application in Electro discharge machining process?
a) Tubular type electrodes
b) Cylindrical type electrodes
c) Flat type electrodes
d) Spherical type electrodes
Answer & Explanations
Answer: b
Explanation: Standard cylindrical electrodes are used for milling application in EDM process.
118. Which type of cavities can be machined using milling process by Electro discharge machining?
a) Complex cavities
b) Simple cavities
c) Simple & Complex cavities
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: Simple cavities and complex cavities are machined by successive NC sweeps of electrode over the desired path.
119. The simple electrodes are rotated at which speed for milling of work pieces in Electro discharge machining?
a) Very low
b) Low
c) Medium
d) High
Answer & Explanations
Answer: d
Explanation: Simple electrodes are rotated at high speeds for milling in Electro discharge machining same as that of conventional milling.
120. What happens to the dielectric flushing while milling tool is rotated at a high speed in EDM?
a) Improved
b) Worsen
c) Reduced
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: Milling by electro discharge machining enhances the dielectric flushing due to high speed rotation of tool.
121. State whether the following statement is true or false regarding the applications of EDM.
“In EDM, milling process can machine complex shapes with sharp corners.”
a) True
b) False
Answer & Explanations
Answer: b
Explanation: EDM milling has a main limitation i.e.., it cannot machine complex shapes with sharp tools because of rotating tool.
122. Which of the following are the steps included in the die sinking process of EDM?
a) CAD of electrode
b) Electrode manufacturing
c) Programming for die sinking
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Designing of electrode, then manufacturing, and programming of die sinking are the steps to be followed for die sinking process in EDM.
123. Wire EDM is a special form of Electro discharge machining which contains __________ electrode.
a) Continuously moving
b) Periodically moving
c) Discontinuously moving
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: Wire EDM is a special type of EDM which uses a continuously moving electrode for removal of material.
124. Which path of the components in wire EDM determines the path to be machined?
a) Horizontal worktable movement
b) Vertical worktable movement
c) Horizontal & Vertical worktable movement
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: Horizontal movement of the work table determines the path to be machined in Wire Electro discharge machining.
125. Which of the following materials are machined using Wire Electro discharge machining?
a) Polycrystalline diamond
b) Cubic Boronitride
c) Matrix composites
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Polycrystalline diamond (PCD), cubic boron nitride (CBN) and other matrix composites are the material than can be machined using wire EDM.
126. How much amount of burr is produce when we use Wire Electro discharge machining for machining of work pieces?
a) 10%
b) 20%
c) No burr
d) Small amount
Answer & Explanations
Answer: c
Explanation: In Wire Electro discharge machining no burr is produced without any distortion while machining work pieces.
127. Which of the following industries use wire EDM for different applications?
a) Chemical industry
b) Aerospace industry
c) Automobile industry
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Industries such as chemical, aerospace, automobile, nuclear etc.., use wire EDM for a wide variety of applications in their industries.
128. While machining insulating ceramic materials using EDM, where is the sheet metal placed?
a) Over material
b) Below material
c) Under material
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: Sheet metal is placed over the material in machining of insulating materials using EDM.
129. Sparks occur between which of the following components?
a) Work piece and sheet metal
b) Tool electrode and sheet metal
c) Work piece and electrode
d) None of the mentioned
Answer & Explanations
Answer: b
Explanation: Sparks occur between sheet metal and tool electrode for macining insulating ceramics.
130. Texturing is applied to the steel sheets at which stages of cold rolling?
a) Initial stages
b) Middle stages
c) Final stages
d) All of the mentioned
Answer & Explanations
Answer: a
Explanation: At the final stages of cold rolling, texturing is applied to the steel sheets.
131. What is the full form of EDT in EDM processes?
a) Electro discharge Tinplating
b) Electro discharge Texturing
c) Electro discharge Tapping
d) Electro discharge Turing
Answer & Explanations
Answer: b
Explanation: Electro Discharge Texturing is a variant of EDM which is the full form of EDT.
132. Which of the following are the process variables for texturing process in EDM?
a) Pulse current
b) Electrode polarity
c) Dielectric type
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Pulse current, polarity, dielectric, electrode material and roll rotation speed are some process variables of texturing.
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133. What are the values of current amplitudes used in EDT?
a) 0.2 to 1 A
b) 2 to 10 A
c) 20 to 100 A
d) 40 to 200 A
Answer & Explanations
Answer: b
Explanation: The values of current amplitudes in EDT range from 2 to 10 A.
134. What are duration values of current amplitude in EDT?
a) 0.1 to 1 µs
b) 1 to 10 µs
c) 10 to 100 µs
d) 100 to 1000 µs
Answer & Explanations
Answer: c
Explanation: Duration of current amplitudes used for EDT range from 10 to 100 µs.
135. What are the spindle rotation speeds used in EDT?
a) 1 to 4 rpm
b) 10 to 40 rpm
c) 20 to 60 rpm
d) 30 to 90 rpm
Answer & Explanations
Answer: b
Explanation: Spindle rotation speeds for EDT process range from 10 to 40 rpm.
136. What are the values of diameter which are machined using Micro-EDM?
a) 0.001 to 0.01 mm
b) 0.01 to 0.1 mm
c) 0.1 to 1 mm
d) 1 to 10 mm
Answer & Explanations
Answer: c
Explanation: Values of diameter in Micro-EDM range from 0.10 to 1.0 mm.
137. What happens to the machine capital cost in EDT when there is an increase in tool quantity?
a) Decreases
b) Increases
c) Remains same
d) None of the mentioned
Answer & Explanations
Answer: b
Explanation: With increase in tools quantity machine cost increases but texturing cost reduces.
138. What is the value of depth to diameter ratio in Micro-Electro discharge machining process?
a) 10:1
b) 5:2
c) 4:3
d) 2:1
Answer & Explanations
Answer: a
Explanation: Value of the depth to diameter ratio in Micro-Electro discharge machining is about 10:1.
139. What are the values of depths that can be machined using Micro-EDM?
a) 1 mm
b) 10 mm
c) 100 mm
d) 1000 mm
Answer & Explanations
Answer: c
Explanation: Micro-Electro discharge machining can machine up to a depth of 100 mm in the work piece material.
140. What are the machining rates used in Micro-EDM process?
a) 0.1 to 2 mm/min
b) 1 to 20 mm/min
c) 10 to 200 mm/min
d) 100 to 500 mm/min
Answer & Explanations
Answer: b
Explanation: Machining rates used in Micro-EDM process range from 1 to 20 mm/min.
141. What are the values of hole diameters obtained using Wire electro discharge grinding?
a) 1 µm
b) 3 µm
c) 5 µm
d) 7 µm
Answer & Explanations
Answer: c
Explanation: Values of hole diameters up to 5 µm can be obtained using Wire electro discharge grinding process.
142. What are the feed rates used in WEDG process?
a) 1 to 5 mm/min
b) 5 to 10 mm/min
c) 10 to 15 mm/min
d) 15 to 20 mm/min
Answer & Explanations
Answer: b
Explanation: Feed rate values in WEDG process range from 5 to 10 mm/min.
143. Which of the following is a major difficulty in the Electro discharge machining process?
a) Proper sparks
b) Abnormal discharges
c) Optimum feed rates
d) No burr
Answer & Explanations
Answer: b
Explanation: Avoidance of abnormal discharges has become a major difficulty in Electro discharge machining process.
144. What has been done to the off time when there is a no-load voltage of electric discharge?
a) Increased
b) Decreased
c) Reduced
d) Remains same
Answer & Explanations
Answer: a
Explanation: The off time of pulse is increased in order to avoid the abnormal electric discharges.
145. In a simple application which of the following parameters are inputs?
a) Pulse duration and current
b) Normal and abnormal pulses
c) All of the mentioned
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: Inputs used are pulse duration and current in a simple application.
146. In a simple application which of the following parameters are outputs?
a) Pulse duration and current
b) Normal and abnormal pulses
c) All of the mentioned
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: Outputs used are normal and abnormal pulses in a simple application.
147. Which of the following are correlated with the machining conditions at output stage?
a) Machining depth
b) Surface roughness
c) Accuracy
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: Machining depth, surface roughness, accuracy are correlated with the machining conditions at the output stage.
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148. How are EDM’s levels of integration when compared to conventional machining?
a) Slower rate
b) Faster rate
c) Same rate
d) None of the mentioned
Answer & Explanations
Answer: a
Explanation: EDM’s levels of computer integration is at a slower rate when compared to conventional machining processes.
149. Manufacturing of tool electrode undergoes which of the following processes?
a) Milling
b) Turning
c) Finishing
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: The tool electrode manufacturing used in EDM has to undergo the basic production processes such as milling, turning and finishing.
150. High temperatures produced in the working gap results in which of the following potentials?
a) Hazardous smoke
b) Toxic vapours
c) Aerosols
d) All of the mentioned
Answer & Explanations
Answer: d
Explanation: The temperatures in the working gap increases leading to hazardous smoke, vapours and aerosols.
151. Hydro carbons present in the dielectric fluid have impact on which of the body parts?
a) Eyes
b) Teeth
c) Skin
d) Nails
Answer & Explanations
Answer: c
Explanation: Hydrocarbons present in dielectric fluids of EDM will have a negative impact on the skin in our body.
152. What happens to the Electro discharge machining process under unfavourable working conditions?
a) Will remain stable
b) Explosion may occur
c) Machining rate increases
d) Nothing happens
Answer & Explanations
Answer: b
Explanation: Explosion occurs if Electro discharge machining is done under unfavourable process variables and conditions.
153. Reduction in the electrical energy consumption will have impact on which aspects mentioned below?
a) Environmental
b) Economic
c) Environmental & Economic
d) None of the mentioned
Answer & Explanations
Answer: c
Explanation: The reduction of electric energy consumption has economic as well as environmental benefits.
