This set of Casting, Forming and Welding Multiple Choice Questions & Answers (MCQs) focuses on “Core Making Machines”.
1. In core making operation, core sand without binder and moisture is used to increase hardness.
a) True
b) False
View Answer
Explanation: In the core making process, core sand is used which is also known as oil sand. It is high rich silica sand that blends with oil binders such as core oil which is a combination of linseed oil, resin, mineral oil and other bind substances. Flours and water can also be used in making of large cores which is a very economical way.
2. Cores can be made within the mould by using moulding sand which is used for mould preparation.
a) True
b) False
View Answer
Explanation: The cores are compact mass of core sand which is a special kind of sand. And cores are always prepared separately and then placed in mould cavity at a required location with proper alignment and accuracy. Core does not allow the liquid metal to occupy space for solidification in that part and hence help to produce hollowness in the casting component.
3. The permeability of core sand is generally kept higher as compared to that of moulding sand in core making operation.
a) True
b) False
View Answer
Explanation: In the core making process, the permeability of the core sand should be sufficiently high as compared to that of the moulding sand. So the core gases easily escape through the area of the core recesses which is generated by the core prints. And the core sand should also be of highly refractoriness in nature to sustain high temperature of molten metal.
4. Better collapsibility of core sand in core making process can ease the cleaning of castings.
a) True
b) False
View Answer
Explanation: The core sand must be collapsible in nature, i.e. it should be disintegrate easily after the metal solidifies in the mould cavity, this property can ease the cleaning of the castings. For a sufficient degree of collapsibility, adequate core binders should be used in core making process which also increases strength of core.
5. Inorganic type of core binders is generally preferred as compared to organic core binders in core making procedure.
a) True
b) False
View Answer
Explanation: In general, the binders are present as inorganic as well as organic ones, but for the core making process, organic binders are normally preferred because they are combustible and can be easily destroyed by the heat at high temperatures thereby providing the sufficient collapsibility to the core sand.
6. Which of the following materials is used for imparting strength and collapsibility in core sand during core making process?
a) Molasses
b) Core oil
c) Sulphite binder
d) Thermo-setting resin
View Answer
Explanation: Thermo-setting resin is very popular in core making because it imparts high strength, collapsibility to core sand and it also emits a minimum amount of mould and core gases which can produce defects in the casting component. The most general binders under this category are phenol formaldehyde and urea formaldehyde.
7. Uniform and homogenous mixture of core sand can be achieved by manual operation.
a) True
b) False
View Answer
Explanation: Preparation of uniform and homogenous mixture of core sand cannot be possible manually. So for better and uniform core sand properties using proper sand constituents and binders, the core sands are generally blended with the help of roller mills or core sand mixer which uses vertical revolving arm type and horizontal paddle type mechanisms.
8. In core blowing machines, the filling of core sands in core boxes is done by using compressed air.
a) True
b) False
View Answer
Explanation: The basic principle of core blowing machine constitutes of filling the core sands into the core boxes by using compressed air. The velocity of the air is kept high to get a high velocity of core sand particles that ensures their deposit in every corner of the core box. On entering of core sand with high velocity, the shaping and ramming of core are performed simultaneously in the core box.
9. In core sand preparation, roller mills are suitable for core sand that contains only a single binder called cereal binders.
a) True
b) False
View Answer
Explanation: In the case of roller mills, the rolling function of the mulling machine along with the turning over movement caused by the ploughs gives a satisfactory and homogeneous mixing of core sand. Roller mills are only suitable for core sands that contain cereal binders, whereas the core sand mixer can be suitable for all types of core binders.
10. A low viscous fluid as lubricant is basically used for extraction of cores from the core boxes.
a) True
b) False
View Answer
Explanation: After ramming of sand, the core box is put on a core plate supported by the machine bed. A rapping action is generated on the core box by vibrating a vertical plate. This rapping action helps in extracting the core from the core box. After rapping the core box, the core is pulled up and gets onto the core plate.
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