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The correct answer is (d) Dry sand molding

The explanation: Among the FOUR METHODS of molding MENTIONED here, dry sand molding offers better accuracy in DIMENSIONS than the green sand molding types mentioned.

The correct choice is (C) Turn-over method molding

Best explanation: The following figure REPRESENTS a turn-over method of molding, where the drag FLASK is KEPT over the pattern.

Correct answer is (b) Squeezing

Easiest explanation: In squeezing, we apply force with the help of a RAM. Due to applied pressure ramming of SAND takes place but the same LOAD is not able to transmit to the bottom of the mold resulting in LOWER STRENGTH at the bottom portion of the mold. But, in jolting impact force act at the bottom. In jolt and squeezing, uniform strength will be achieved. In hand molding, strength will be non-uniform.

Correct ANSWER is (c) Magnesium

The explanation is: Magnesium which is PRESENT in small quantity INSIDE the light alloy, when REACTS with WATER, causes the formation of hydrogen filled pinholes.

Right option is (B) False

Explanation: For MAINTAINING the proper venting, the pouring time cannot be increased because that will cause other problems in the CASTING process such as early solidification which will form the incomplete sections in the casting and several defects in the casting components like cracks and SHRINKAGES.

The correct ANSWER is (B) False

Easy explanation: After the SOLIDIFICATION of the casting component, the sand mould is broken and the casting part is EXTRACTED from the broken mould. This process is also known as SHAKEOUT and it is commonly performed by a vibrating machine or tool that shakes the sand particles and then the casting comes out from the flask.

The CORRECT option is (c) Mould making

Best explanation: The first step involved in the SAND casting method is to produce the mould for the casting. In an expendable MOULDING process, this step should be done for each DIFFERENT casting. A sand mould is basically produced by packing sand mass into each half of the mould. The sand mass is rammed near at the pattern side; pattern is a replica of the casting to be made.

Correct choice is (b) False

Explanation: In SQUEEZING method of ramming, the RESULTING force COMPACT the sand uniformly and the hardness achieved directly depends to the pressure applied on the plate. More the pressure more will be the hardness of the sand, but the sand NEXT to the plate rams hardest while the sand below is progressively less hard.

Right answer is (d) Hand molding

Explanation: In hand molding operation the force required for RAMMING the mold is applied by human hand THUS the TIME taken for making the mold is longer. This LEADS to the least production RATE when compared with the above processes. Whereas in other methods machines are used reducing the production time.

Right answer is (a) Hand moulding

The explanation is: For the small batch production, it is very convenient to USE the hand moulding METHOD of RAMMING which is done manually and REST of the methods are mainly performed by the machines. So, it is very economical and time saving to use hand moulding for the small level production of CASTINGS.

Right answer is (b) Deoxidizing

The best I can EXPLAIN: When PINHOLES are being PRODUCED more than necessary, the metal-mold reaction has to be deoxidized, which can cause the pinholes to reduce.

The correct choice is (a) True

To elaborate: Porous sintered MATERIALS can be placed in the mould cavity to act as a vent. It MAINLY depends on the thickness of the porous MATERIAL used. More the thickness, then less will be the venting capacity. So venting passages should be machined properly to collect the gases, proper CLEANING of vents is also important as the gas DEPOSITS can block the passages.

Right choice is (a) True

For explanation I would say: Generally, the hardness achieved follows the contour of the squeeze plate which is in CONTACT with the sand, Contour is always provided with the plate to match the pattern to ACHIEVE a better uniform hardness of the mould. So, application of contour is very ESSENTIAL for better and EFFICIENT RAMMING.

The CORRECT answer is (a) True

Best explanation: In mould making process, the moulding TIME generally involves positioning of pattern, sand ramming and pattern extraction from the moulding box. The mould making time is greatly affected by the size and SHAPE of the casting components, number of cores, and the type of sand mould USED in the process.

Correct choice is (a) True

The explanation is: The molten metal is poured into the mould cavity that begins to cool and solidify. During solidification, most of the defects which may OCCUR are a result of the solidification process. If the molten metal solidifies too quickly, then the casting parts may EXHIBIT defects LIKE shrinkage, CRACKS or blow holes.

Right CHOICE is (a) True

Explanation: Hand RAMMERS are used for RAMMING sand in BENCH mold. It can be made up of either METAL or it could be of wood too. The material depends on the type of operation.

Right ANSWER is (a) OPEN sand method MOLDING

Best explanation: Castings which are simple with tops being FLAT, can be produced from the open sand molding method.

The correct answer is (a) Air cooling

Best explanation: AMONG the following processes, air cooling is not a type of hand MOLDING PROCESS, while the remaining other processes are hand molding processes.

Right ANSWER is (B) False

The best explanation: In the mould, the core experiences the static pressure as well as the weight of the core. When these two worked together in combination, then there is a lifting of the core due to the FORCE which is called as buoyancy force. This force acts onto the core because of the DENSITY difference of the molten metal and the core material USED.

Correct choice is (d) NOZZLE

The explanation: In the sand slinging method of RAMMING, the sand is uniformly sprayed into the mould by moving the nozzle through the entire area of the flask. Also, it is necessary that the sand is sprayed in layers to achieve uniform HARDNESS. This method is very ECONOMICAL and widely used for ramming.

The correct ANSWER is (d) OVERHEAD hopper

For EXPLANATION I would say: Basically, an overhead hopper is used in jolt mould method of ramming, in which after filling the sufficient amount of sand to the mould, an overhead hopper is raised to a certain height and then it is allowed to free fall on to a solid bed plate, which RESULTS into the ramming and packing of sand layers in the mould.

Correct choice is (b) Button smoother

For explanation I would say: The hand molding equipment which is SHOWN in the figure is a button smoother. They ensure the REPAIRING work of the casts. Not just that, they ALSO HELP in the finishing work.

The correct choice is (B) BEDDED-in method molding

The best explanation: If the requirement of the casting is that, its UPPER surface should be SMOOTH, bedded in the method should be used.

Right choice is (b) False

Explanation: In the method of JOLT moulding, it gives RISE to uneven packing and it is very severe on the moulding equipment also. The sand at the bottom experiences the highest force and the magnitude of the force is decreases in UPWARD direction, so the bottom layers packed well as compared to the top layers in the mould.

The correct answer is (C) JOLTING

To explain: During jolting, the sand-filled mold is taken to a certain height so that it possesses potential energy and then ALLOWED to FALL freely onto the GROUND. Due to impact force transmitted to the bottom of the mold is very high when compared to the top of the mold that leads to high strength at the bottom and low strength at top of the mold.

The correct choice is (C) The property to withstand HIGHER metallostatic PRESSURES during casting

The best I can explain: The Nobake moulding process provides a good STRENGTH of mould, hence, it can withstand the metallostatic pressures and can give good dimensional TOLERANCES.

Right OPTION is (c) Jolting

To explain I would SAY: In jolting, we only need to take the mold to a certain height and then drop it. Thus highest production rate of the is achieved. Sand slinging requires more time as it is a repetitive PROCESS. Jolt and squeezing combines both jolting and squeezing hence will take more time than jolting. In squeezing, we need to keep the force for a certain time which REDUCES the production rate.

The correct OPTION is (a) Furan or Urethane

The EXPLANATION is: Nobake is a moulding process that involves the use of furan (CHEMICAL BINDERS) to bond the moulding SAND.

The CORRECT option is (d) 300°F – 650°F

To explain I would say: To CONVERT GREEN sand into dry sand, the green sands are heated to a fairly good amount of temperature. This temperature would range in between the RANGES of 300°F to 650°F.

Right OPTION is (c) Rubber PLASTER Moulding

The best EXPLANATION: R.P.M stands for Rubber Plaster Moulding. RPM is also KNOWN as plaster moulding, since, use of plaster of paris is done in this process.

The correct answer is (B) False

Best explanation: Green sand MOLD is FOUND to contain a very LOW AMOUNT of strength and a low amount of permeability.

Correct choice is (c) Non-uniform STRENGTH

The explanation: In hand MOLDING, the ramming force required for compressing the molding SAND is applied by HUMAN hand. A human knows about projection in the pattern ACCORDINGLY he applies force thus no damage to projections. Surface finish obtained is also good.But, the force applied is non-uniform which results in non-uniform strength.

Right ANSWER is (b) Decreases with ramming

The BEST explanation: The permeability of green sand decreases with an intensity of ramming DONE on the sand. Hence, the amount of CLAY is adjusted to keep permeability in a profitable ZONE.

The correct option is (a) Increases bulk DENSITY

The EXPLANATION: The increased DEGREE of ramming RESULTS in an increase of bulk density or hardness of sand.

The CORRECT choice is (d) Sodium SILICATE

The best explanation: Sodium silicate is the PRINCIPLE binder used in carbon DIOXIDE moulding process. The mixture of sodium silicate and sand is TREATED with carbon dioxide to form a bond.

The correct answer is (C) 72 HOURS

The explanation: The mold in cement bonded sand is ALLOWED to get SET, get dry and get cured for about 72 hours before POURING.

Correct choice is (c) RESIST CORROSION

Explanation: Resisting corrosion is not any of the characteristics of molds while REMAINING others are COUNTED as mold characteristics.

The correct CHOICE is (b) The sand is TAKEN out of the MIXTURE

The EXPLANATION is: A mixture is used to BLEND the sand with chemical binder. The chemical hardening starts when this sand exits the mixture.

The CORRECT answer is (a) Low permeability

The BEST I can explain: The DRIED PLASTER moulds have extremely low permeability, about- 1 to 2 AFS.

Right CHOICE is (a) True

To elaborate: A SKIN DRIED MOLD cannot be made to wait after drying and has to be immediately poured, else, it may CATCH the moisture from green sand and may become ineffective.