Manufacturing Engineering Multiple Choice Questions on “Extrusion”.
1. In which process the cross section of the metal is reduced by forcing it to flow through a die under high pressure?
a) Forging
b) Forming
c) Extrusion
d) Welding
Answer: c
Clarification: Extrusion is a process that uses a die in order to get a material with a constant cross-sectional cut. The die is what the material is pushed through in order to get the desired shape. Each product has a specific die that will create that shape and characteristic. Extrusion is used with materials such as plastic, aluminum, and dough. These products are either too brittle or too soft to be formed using bending or hammering, so in order to form the desired shapes extrusion is necessary.
2. Which of the following is a type of extrusion process?
a) Direct
b) Indirect
c) Impact
d) All of the mentioned
Answer: d
Clarification: Classification of extrusion processes are shown below.
3. Which of the following is true about the extrusion process?
a) Structure is homogeneous
b) No time is lost in changing the shape
c) Service life of extrusion tool is too high
d) Its leading end is in good shape as compared to rolling
Answer: b
Clarification: No time is lost in changing the shape as the dies may be readily removed in the process of extrusion.
4. In which extrusion process the direction of flow of metal is in same direction as that of ram?
a) Direct
b) Indirect
c) Impact
d) Hydrostatic
Answer: a
Clarification: Direction extrusion is a process in which the metal billet, placed in a container is forced by a ram to pass through a die. In this type, the direction of flow of metals is, in same as that of movement of ram. The punch closely fits the die cavity to prevent the backward flow of the material.
5. In direct extrusion process at higher temperature which of the following is used to avoid friction?
a) Oil
b) Lubricants
c) Molten glasses
d) Wax
Answer: c
Clarification: For steels, stainless steel, and high temperature materials, glass is a good excellent lubrication. The reasons for this are as follows. i. Glass contains its viscosity at elevated temperatures, ii. Has good wetting characteristics, and 3. Glass acts as a thermal barrier between the billet, the container and the die, thus minimizing cooling.
6. Which of the following is not used because of the problem of handling extruded metal coming out through moving ram?
a) Direct
b) Indirect
c) Impact
d) Hydrostatic
Answer: b
Clarification: Indirect extrusion method is not used because of the problem of handling extruded metal coming out through moving ram.
7. Which of the following is not a cold extrusion process?
a) Cold extrusion forging
b) Impact extrusion
c) Hydrostatic extrusion
d) Cold rolling
Answer: c
Clarification: Cold extrusion is done at room temperature or near room temeprature. The processes, impact extrusion, hydrostatic extrusion and cold extrusion forging are the types of cold forging. The advantages of this over hot extrusion are the lack of oxidation, higher strength due to cold working, closer tolerances, and good surface finish.
8. In which of the following process frictional loss is eliminated at the billet container interface?
a) Direct
b) Indirect
c) Impact
d) Hydrostatic
Answer: d
Clarification: In hydrostatic extrusion process frictional loss is eliminated at the billet container interface. This elimination increases the quality of the product.
9. In which of the following process fluid medium is used to apply the load on the billet?
a) Direct
b) Indirect
c) Impact
d) Hydrostatic
Answer: d
Clarification: In hydrostatic extrusion process fluid medium is used to apply the load on the billet. As hydro stands for fluid and static for rest.
10. Extrusion is similar to?
a) Rolling
b) Forming
c) Welding
d) Casting
Answer: a
Clarification: Extrusion is similar rolling in producing constant cross-sectional shape.
11. Which defect arises due to high friction or high speed?
a) Tearing
b) Surface cracking
c) Tearing & Surface cracking
d) Flaking
Answer: c
Clarification: The defects such as, surface cracking and tearing, occurs with high friction or speed. These can also occur with stickling of billet material on die land. Material sticks, pressure increases, product stops and starts to move again. This produces circumferential cracks on surface like a bamboo stem.
12. Which of the following defect is also known as bamboo defect?
a) Blow hole
b) Cold shut
c) Surface cracking
d) Pipe defect
Answer: c
Clarification: Bamboo defects are periodic surface cracks that develop due to the extruded product sticking to the die land.
13. Which of the following defect tends to draw surface oxides and impurities towards the centre of billet?
a) Blow hole
b) Cold shut
c) Surface cracking
d) Pipe defect
Answer: d
Clarification: Pipe defect is the formation of sin hole at the end of the billet. It is associated with direct extrusion. The use of dummy blocks whose diameter is slightly less than that of the billet helps to avoid piping.
14. Which of the following defect is also known as fish tailing?
a) Surface cracking
b) Pipe defect
c) Tearing
d) Internal cracking
Answer: b
Clarification: In extrusion, the pipe defect is also termed as “tail pipe”, and “fish tailing”. It occurs during hot extrusion due to the presence of impurities and oxides.
15. The centre of the extruded product can develop cracks called as?
a) Centre cracking
b) Centre burst
c) Arrow headed fracture
d) All of the mentioned
Answer: d
Clarification: Cracks that are developed in the centre of extruded material is known as internal cracking. These are termed as “centre cracking”, “centre burst”, “chevron cracking”, and as “arrow head cracking”.