Advanced Machining Processes Multiple Choice Questions on “EDM-Mechanism of Material Removal – 2”.
1. 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: b
Clarification: Debris is carried away by the fresh dielectric that rushes in.
2. The layer formed when unexpelled molten metal solidifies is known as _______________
a) Reabsorbed layer
b) Recast layer
c) Unevaporated layer
d) Condensed layer
Answer: b
Clarification: Unexpelled molten metal solidifies to form a layer known as recast layer.
3. 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: c
Clarification: The amount of material removed from electrodes depend on the contribution of the charged ions.
4. 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: a
Clarification: When electron current predominates the electrical discharge, anodic material removal is greater than cathodic material.
5. 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: b
Clarification: Frequency of discharges or sparks generally vary between 500 and 500,000 sparks per second.
6. 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: c
Clarification: In EDM, value of gap maintained between the electrodes range between 200 and 500 µm.
7. 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: d
Clarification: Based on the electrode gap, electric pulses are distinguished which are – circuit pulses, sparks, arcs and short circuits.
8. 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: a
Clarification: In Electro discharge machining, electric pulses generated have an impact on the material removal.
9. Open gap voltages contribute to how much amount of material removal?
a) 20 %
b) 50 %
c) 70 %
d) No contribution
Answer: d
Clarification: Open gap voltage that occur at too large distances do not contribute to any material removal.
10. 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: d
Clarification: When electrodes come in contact with one another, short circuits occur and material removed is not possible.
11. Which components mentioned below are affected due to arcs?
a) Work piece
b) Tool
c) Work piece & Tool
d) None of the mentioned
Answer: c
Clarification: Arcs are believed to occur at same spots on electrode surfaces which damage both tool and work piece.
12. 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: d
Clarification: The sparks are the one which contributes to the desired material removal in Electro discharge machining.