Manufacturing Engineering Multiple Choice Questions on “Gating design”.
1. In which type of gating system aspiration effect takes place?
a) Vertical
b) Horizontal
c) Diagonal
d) Bottom
Answer: a
Clarification: When the molten metal is flowing through gating system and if somewhere along the gating system pressure fall below the atmosphere pressure, due to high velocity of molten metal then air from outside start flowing into the gating system due to pressure difference between atmospheric air and flow pressure, this effect is called as aspiration effect. Aspiration effect takes place in a vertical gating system. Aspiration effect leads to the formation of blow holes in the casting.
2. In the gate area for non-pressurized casting gating ratio a:b:c? (gating ratio = a: b: c where, a = cross-sectional area of sprue, b: cross-sectional area of runner, c = total cross-sectional area of ingates).
a) 1:2:2
b) 2:2:1
c) 1:4:4
d) 1:4:2
Answer: c
Clarification: The gating ratio may be of the order of 3:2:1 for pressurized gating system and for unpressurized gating system is will be in 1:3:2. The further differences between pressurized and non-pressurized gating system are tabulated below:
| S.No. | Pressurized gating systems | Unpressurized gating systems |
|---|---|---|
| 1 | Gating ratio may be of the order of 3:2:1 | Gating ratio may be of the order of 1:3:2 |
| 2 | Air aspiration effect is minimum | Air aspiration effect is more |
| 3 | Volume flow of liquid from every ingate is almost equal | Volume flow of liquid form every ingate is different |
| 4 | They are smaller in volume for a given flow rate of metal. Therefore, the casting yield is higher. | They are larger in volume because they involve large runners and gates as compared to pressurized system and thus the cast yield is reduced. |
| 5 | Velocity is high, severe turbulence may occur at corners. | Velocity is low and turbulence is reduced. |
3. Which of the following is not a type of riser?
a) Top riser
b) Open riser
c) Internal riser
d) Bottom riser
Answer: d
Clarification: In casting process there are mainly two types of raisers are used: 1. Open riser (top riser), 2. Blind riser (side riser). Blind risers are good design features and maintain heat longer than open risers too.
4. Caine curve is a graph between?
a) Volume ratio and solidification ratio
b) Volume ratio to freezing ratio
c) Volume ratio to heating ratio
d) Freezing ratio to time ratio
Answer: b
Clarification: Caine curve is a graph between volume ratios to freezing ratio. Caine curve is used to determine exact volume for perfect freezing.
5. To prevent heavier and lighter impurities which of the following system is used?
a) Skim bob
b) Pouring basin
c) Strainer
d) Splash core
Answer: a
Clarification: Skim bob is a hollow above the runner that acts to skim off floating dross, sand and debris so it does not enter the casting.
6. To reduce the eroding force of the liquid metal which of the following system is used?
a) Skim bob
b) Pouring basin
c) Strainer
d) Riser
Answer: b
Clarification: The pouring basin or pouring cup is used to make the pouring operation easy and effective without losing the molten metal. Without a pouring basin with the right dimensions it would be hard to pour the metal from a ladle.
7. If velocity of metal flow at gate is 4m/sec, volume of mould is .1 cubic meters and the cross-sectional area of gate is 0.002 cubic meters then the time required to fill up the mould in seconds is?
a) 10
b) 12
c) 12.5
d) 15.5
Answer: c
Clarification: t = [v/ (a*V)], where v is volume, V is the velocity, a is the area and t is the time taken to fill the mould.
8. If the volume to surface area ratio is 2 for riser and for casting it is 4, then the freezing ratio is?
a) 2
b) 4
c) 8
d) .5
Answer: d
Clarification: The freezing ratio (x) of the mould is defined as the ratio of cooling characteristics of casting to the riser:
x = (displaystylefrac{(frac{surface ,area}{volume})_{casting}}{(frac{surface ,area}{volume})_{riser}})
Freezing ratio, as per the given values in the question, x = (displaystylefrac{(frac{surface ,area}{volume})_{casting}}{(frac{surface ,area}{volume})_{riser}} = frac{2}{4}) = 0.5.
9. Time required to fill the mould by vertical gating system is?
a) Less to bottom gating system
b) More to bottom gating system
c) Equal to bottom gating system
d) Sometimes more and sometimes less to bottom gating system
Answer: a
Clarification: Time required to fill the mould by vertical gating system is less than bottom gating system.
10. A mould has a down sprue length of 0.2 meters. The velocity of metal in meter/second at gate will be?
a) 1.78
b) 1.98
c) 2.3
d) 2.5
Answer: b
Clarification: Velocity = (sqrt{(2*g*h)}), where h is the length of down sprue, and g is the value of earth gravity which can be taken as 9.81.