Category: Manufacturing Engineering Objective Questions

250+ TOP MCQs on Gating design and Answers

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.

250+ TOP MCQs on Metal Solidification and Fluid Flow and Answers

Manufacturing Engineering Multiple Choice Questions on “Metal Solidification and Fluid Flow”.

1. Grains created when a metal solidifies rather slowly in the presence of a steep temperature gradient fall in the category of?
a) equiaxed grains
b) columnar grains
c) elongated grains
d) planer grains
Answer: b
Clarification: Columnar grains are long, thin, coarse grains created when a metal solidifies rather slowly in the presence of a steep temperature gradient. Relatively few nuclei are available when columnar grains are produced.

2. Vacancies are _____________
a) planer defects
b) line defects
c) point defects
d) volume defects
Answer: c
Clarification: Vacancy defect is the simplest point defect. In this system, an atom is missing from its regular atomic site, vacancies are formed during solidification due to vibration of atoms.

3. Scanning tunneling microscope is a tool usually used to analyze an image at ____________
a) sub-atomic level
b) atomic level
c) micro level
d) macro level
Answer: b
Clarification: Scanning tunneling microscope (STM) is a technique that has been used for the surface study of nanostructures using the chemical composition of atoms and molecules in NPs to image surfaces at the atomic level. High-resolution material contrast has been successfully demonstrated in STM photon emission maps that correlate closely with the topographi image.

4. What are the examples of line defect?
a) vacancies
b) dislocations
c) twins
d) stacking faults
Answer: b
Clarification: Line imperfections, or dislocations, in crystalline solids are defects that cause lattice distortion centered around a line.

5. A mixture of a metal(s) and a non-metal(s) is called?
a) composite
b) alloy
c) dislocation
d) cermet
Answer: b
Clarification: A mixture of metal and non-metal is termed as an alloy, whereas a combination of two different materials (may not have metal in it) is called as composite.

6. If there are 930 grains per mm2 on a photomicrograph of a metal at 2X, what is the ASTM grain size number of the metal?
a) 6
b) 7
c) 7.92
d) 8.91
Answer: d
Clarification: If there are 930 grains per mm2 at 2X, then at 1X we will have
N‘ = (2/1)2 (930 grains/mm2) = 3720
therefore, N = N‘/15.5 = 3720/15.5 = 240
240 = 2n-2
log 240 = (n-1)(log 2)
2.380 = (n-1)(0.301)
n = 8.91.

7. An ASTM grain size determination is being made from a photomicrograph of a metal at a magnification of 1X. What is the ASTM grain size number of the metal if there are 992 grains per square mm?
a) 6
b) 7
c) 7.92
d) 8.91
Answer: b
Clarification: N = 2n-1
where, N = no of grains per square inch at 100X
n = ASTM grain size number
and N is obtained using the following expression:
N = N‘/15.5 where N‘ = no. of grains per square mm at 1X
Thus, N = 992/15.5 = 64
or, 64 = 2n-1
log 64 = (n-1)(log 2)
n = 7.

8. Risers are also called __________
a) spure
b) runners
c) feeders
d) risers
Answer: c
Clarification: Risers also called feeders serve as reservoirs of molten metal to supply any molten metal necessary to prevent porosity due to shrinkage during solidification.

9. In a free-falling liquid, the cross-sectional area of the stream?
a) increases
b) decreases
c) remains constant
d) first increases and then decreases
Answer: b
Clarification: In a free falling liquid, the cross sectional area of the stream decreases as the liquid gains velocity downward.

10. If the pouring basin has a much larger cross-sectional area than the sprue bottom, then the velocity of the molten metal is?
a) low
b) high
c) normal
d) either high or low
Answer: a
Clarification: The molten metal flows through a sprue to a runner and a gate and fills the mold cavity. If the pouring basin has a much larger cross sectional area than the sprue bottom, then the velocity of the molten metal at the top of the pouring basin is very low and can be taken to be zero.

250+ TOP MCQs on Roll Forming – 2 and Answers

Manufacturing Processes Interview Questions and Answers on “Roll Forming – 2”.

1. EP 2 grease, high-temperature grease and chain and open-gear grease are used in roll forming equipment.
a) True
b) False
Answer: a
Clarification: EP 2 grease is used lubricating gears. This gear can handle heavy, suddenly applied loads in bearing application. High-temperature grease is used in weld boxes and other equipment that is subjected to a temperature above 200°F. Chain and open-gear grease are used on chain couplings, chain-driven components and open gear drives.

2. Which of the following oils is used in roll forming equipment?
a) SAE 140
b) SAE 30
c) Linseed oil
d) SAE 5W-30
Answer: a
Clarification: ISO grade 460 (SAE 140) Gear oil is used in sealed gearboxes. Gear oil has extreme pressure additives that strengthen the non-detergent oils to withstand heavy loads found in gears and gear drive systems.

3. In how many types roll forming lubricants are categorised?
a) 3
b) 5
c) 6
d) 4
Answer: b
Clarification: The different types of roll forming lubricants are listed below:
1. Evaporator compounds or vanishing oils
2. Chemical solutions (synthetics)
3. Micro-emulsions (semi-synthetics)
4. Macro-emulsions (solubles)
5. Petroleum based lubricants.

4. Chemical solutions (synthetics) ideal for coated steel.
a) True
b) False
Answer: a
Clarification: Chemical solutions are one of the fastest growing roll forming lubricant family. They are economical, environmentally safe, easy to handle, and are ideal for use on coated, galvanised, cold roll steel, aluminium, and in some instances, stainless steel.

5. Which of the following is used for lubrication in heavy-duty roll forming?
a) Extreme pressure-type solutions
b) Soap-type solutions
c) Non-ionic type solutions
d) Micro-emulsions
Answer: b
Clarification: The soap-type solutions are used for heavy-duty roll forming. Non-ionic type solutions are excellent for roll forming aluminium and coated components and extreme pressure-type are used for high strength alloys.

6. For which of the following materials evaporative lubricants are used?
a) Hot rolled steel
b) Stainless steel
c) Ferrous and non-ferrous materials
d) Aluminium
Answer: c
Clarification: Evaporative lubricants are used for roll forming of painted, coated, and vinyl surfaces as well as ferrous and non-ferrous materials. They are applied using the proper type of airless spray system.

7. Which of the following is ideal for lubrication in roll forming of hot rolled and cold rolled steel?
a) Micro-emulsion
b) Macro-emulsion
c) SAE 120
d) SAE 20W 40
Answer: a
Clarification: micro-emulsions provide some film strength from the combination of emulsifiers, water-soluble corrosion inhibitors, wetting agents, organic and inorganic salts, and sometimes extreme pressure agents.

8. Macro-emulsions are also called as soluble oils.
a) True
b) False
Answer: a
Clarification: Macro-emulsions contain an oil-based lubricant, such as a mineral or compounded oil in the form of suspended droplets, which have been dispersed with emulsifiers due to which they become milky white appearance. Therefore, they are sometimes misleadingly called soluble oils.

9. Why additives are mixed with lubricating oil?
a) To reduce the friction
b) To increase the heat transfer
c) To change the colour
d) To improve the lubricant properties
Answer: d
Clarification: Additives are mixed to adjust the lubricants and make the suitable for a specific application. Additives improve lubricant’s properties, protect metal surfaces as well as perform many other functions.
Examples of additives: Rust and corrosion additives, EP additives, etc.

10. Pick the odd one out.
a) Sulphur compounds
b) Nitrates
c) Phosphorous compounds
d) Chlorine compounds
Answer: b
Clarification: Nitrates are usually used as rust or corrosion inhibitors; whereas compounds of sulphur, chlorine and phosphor are extreme pressure additives.

Processes for Interviews,

250+ TOP MCQs on Electrochemical Etching – 8 and Answers

Manufacturing Processes Multiple Choice Questions on “Electrochemical Etching – 8”.

1. Cone-like pores can be obtained by using Lehmann’s law.
a) True
b) False
Answer: a
Clarification: According to the Lehmann’s law, the increasing collection of photo-generated holes results in a progressive reduction of the pore diameter with depth, yielding cone-like pores with decreasing diameter from top to bottom.

2. Progressively modified illumination intensity approach can be used to develop some optical structures.
a) True
b) False
Answer: a
Clarification: This approach can be readily used to develop some optical structures such as photonic crystals and optical waveguides in the visible and NIR range as the refractive index of MpSi can be engineered in depth along the pore yielding a waveguide structure embedded in the array of macropores.

3. Progressively modified illumination intensity approach when combined with lithographic patterning, gives_____
a) straight macropores
b) straight micropores
c) sponge-like pSi
d) honeycomb like pattern
Answer: a
Clarification: Variable illumination intensity technique can be combined with lithographic patterning to produce 2D infrared photonic crystals featuring perfectly ordered and straight macropores.

4. In the technique mentioned in the previous question, arrays of macropores are _____
a) heated to the melting temperature
b) soaked in HF solution for several hours
c) coated by a lithographic mask
d) kept under UV rays
Answer: c
Clarification: In this process, arrays of macropores are coated by a lithographic mask after electrochemical etching. Next, MpSi is selectively removed from the unmasked areas by a wet chemical etching. This results in a set of deep bars of macropore rows with well-defined pore geometry.

5. Which of the following is true according to the Lehmann’s model for the formation of MpSi?
a) The current density is equal to the critical current density
b) The current density is half of the critical current density
c) The critical current density is equal to square of the current density
d) Lehmann’s model does not give relation between current density and critical current density
Answer: a
Clarification: According to the Lehmann’s model for the formation of MpSi, the current density at the pore bottom tips is equal to the critical current density. Therefore, an increment of the illumination intensity at the backside of the silicon wafer during etching leads to the generation of electronic holes, which directly contribute to the total current density.

6. The pore diameter in macroporous silicon can be periodically modulated.
a) True
b) False
Answer: a
Clarification: Following the approach based on the Lehmann’s model, the pore diameter in macroporous silicon can be periodically modulated (Fig. 1.5). This approach takes advantage from the fact that the porosity of the resulting MpSi structure is established by the ratio between the total current density and the critical current density (i.e. JPS—current density limit between the formation of pSi and electro-polishing of silicon).

7. Increase in the total current density produced by the generation of electronic holes increases the pore diameter.
a) True
b) False
Answer: a
Clarification: The critical current density is constant at the pore bottom tips and thus the increment of the total current density produced by the generation of electronic holes widens the pore diameter. Following this procedure, the pore structure of MpSi can be modulated to produce periodic ratchet-type (i.e. asymmetric) or circular (i.e. symmetric) pore modulations.

8. If the etching conditions are not controlled, then _____ decreases with pore depth.
a) the period length
b) diameter of the pores
c) orderliness of the pores
d) reflectivity of the material
Answer: a
Clarification: If the etching conditions are not controlled, the period length, which is defined as the distance between two consecutive pore modulations, decreases with the pore depth due to diffusion limitations (i.e. lower concentration of HF at the pore bottom tips). As a result, the critical current density decreases and the pore growth rate becomes slower.

9. Post-treatment starts with a thermal treatment of the MpSi structure at _____
a) 900°C
b) 1100 °C
c) 1570°C
d) 1650°C
Answer: b
Clarification: A post-treatment is required after the fabrication of MpSi. This post-treatment starts with a thermal treatment of the MpSi structure at 1100 °C for 100 min under oxygen atmosphere.

10. During post treatment of MpSi, a layer of silicon dioxide is formed.
a) True
b) False
Answer: a
Clarification: A thermal treatment of the MpSi structure at 1100 °C for 100 min under oxygen atmosphere generates a silicon dioxide layer of 200 nm along the inner surface of the pores of MpSi.

250+ TOP MCQs on Abrasive Jet Micromachining – 4 and Answers

Manufacturing Processes online test on “Abrasive Jet Micromachining – 4”.

1. Performance of the AJMM process is dependent on the quality of the mask.
a) True
b) False
Answer: a
Clarification: The quality of the mask influences the performance of AJMM. The main qualification for a good mask material is a low erosion rate. It also requires the capability of an accurate and easy pattern transfer, and the ability to retain the irresistance in discontinuous layers.

2. How many types of materials can be used during AJMM?
a) 1
b) 3
c) 8
d) there is no compulsion on the material
Answer: b
Clarification: Three groups of mask materials can be applied to AJMM:
• Ductile materials such as metals.
• Elastic materials such as elastomer sand.
• Photo-resists as used in IC-industry.

3. The usability of the mask is affected by imaging accuracy.
a) True
b) False
Answer: a
Clarification: Each material used for making mask, needs a sufficient erosion resistance related to the substrate especially at normal blast angles. Furthermore, the achievable imaging accuracy determines the usability of a mask and minimum achievable features size.

4. Which of the following have a low erosion rate?
a) Ductile materials
b) Malleable materials
c) Hardened materials
d) Low melting point materials
Answer: a
Clarification: Ductile materials, like metals, have a low erosion rate, especially at perpendicular impact. This makes them suitable to be used as a mask material. It can be used by means of a thin plate (e.g. stainless-steel).

5. To apply metal mask plate for AJMM, magnetic clamps are used.
a) True
b) False
Answer: a
Clarification: Metals having low erosion rates are suitable for making masks for AJMM. To apply metal mask plate for AJMM, it can be magnetically clamped directly to the target or by introducing an intermediate protection/ adhesion layer.

6. Limitations in feature size are the major drawback of the metal masks.
a) True
b) False
Answer: a
Clarification: The disadvantages of this mask type are the limitations in feature size (approximately 50 μm) and pattern constraints (circular patterns cannot be used because the inner side should be supported).

7. In AJMM, metals masks can be applied to the workpiece by electroplating.
a) True
b) False
Answer: a
Clarification: In order to combine the low erosion rate of a metal, and the high resolution of a lithographic process, a metal mask can be applied to the target by electroplating. Copper is used by this method, while Zinc mask can be made by electro-forming.

8. The erosion mechanism of rubber-like materials is same as that of brittle materials and ductile materials.
a) True
b) False
Answer: b
Clarification: The erosion mechanism of rubber-like materials differs essentially from that of brittle materials or ductile materials. No lateral cracks are formed in elastomers as found in brittle materials. Neither do any evidence of cutting or ploughing wear as found in metals.

9. Erosion mechanism in elastomer materials is based on fatigue.
a) True
b) False
Answer: a
Clarification: The erosion mechanism of this class of materials is based on fatigue; therefore they display a good erosion resistance. The photosensitive materials can be patterned accurately using lithography. Photosensitive-elastomer can be a good option.

10. Behaviour of elastomer materials is dependent on temperature.
a) True
b) False
Answer: a
Clarification: In contrast to ductile or brittle materials, elastomers behaviour is dependent on temperature, rate of deformation and particle velocity. Thus elastomers can show ductile, elastic and brittle behaviour.

250+ TOP MCQs on Friction Welding and Answers

Manufacturing Processes Questions and Answers for Campus interviews on “Friction Welding”.

1. Friction welding process is restricted to_____
a) square bars
b) round bars
c) hexagonal bars
d) bars having diameters less than 20mm

Answer: b
Clarification: The process is restricted to joining round bars of same diameter (or bar tubes to flat surfaces), i.e., capable of being rotated about the axis. Furthermore, capital equipment and tooling costs are high and free-machining alloys are difficult to weld.

2. Which of the following materials cannot be welded by friction welding?
a) Aluminium
b) Copper
c) Stainless steel
d) Non-forgeable materials

Answer: d
Clarification: Dry bearing and non-forgeable materials cannot be welded by a friction welding process, i.e., one of the components must be ductile when hot, to permit deformations. Preparation and alignment of the workpieces of the workpieces may be critical for developing for developing uniform rubbing and heating, particularly for pieces having diameters larger than 50mm.

3. In which of the following areas, friction welded products are not used?
a) Aerospace
b) Automotive
c) Marine
d) Toy making

Answer: d
Clarification: Friction welded parts in production application span over wide products for aerospace, agriculture, automotive, defence, marine and oil industries. Right from tong holds to critical aircraft engine components are friction welded in production.

4. Which of the following automotive components are not friction-welded?
a) Gears
b) Engine valves
c) Strut rods
d) Rims

Answer: d
Clarification: Automotive parts that are friction welded include gears, engine valves, axel tubes, driveline components, strut rods and shock absorbers. Rims are generally welded by TIG or MIG welding.

5. Friction welding cannot be used for welding stainless steel to carbon steels.
a) True
b) False

Answer: b
Clarification: Stainless steels are friction welded to carbon steels in various sizes for uses in marine systems and water pumps for home and industrial use. Friction welded aluminium/copper joints are in wide usage in the electrical industry.

6. Friction welded components are cheaper than casted components.
a) True
b) False

Answer: b
Clarification: Friction welded components are comparatively cheaper than casted components. Friction welded assemblies are often used to replace expensive casted and forged components.

7. Which of the following components from agricultural equipment is not friction welded?
a) Track rollers
b) Axles
c) Bushings
d) Cultivator

Answer: d
Clarification: Following are the few components which are friction welded by manufacturers of agricultural equipment;
• Hydraulic piston rods
• Track rollers
• Gears
• Bushings
• Axles
Cultivators are heavy duty machines used for soil cultivation.

8. Aluminium is difficult to friction weld because of _____
a) ductility
b) softness
c) micro porosity
d) heat reflectivity

Answer: c
Clarification: The basic problems with friction welding of aluminium and its alloys are that they possess:
• Cast brittle dendritic structure
• Micro porosity
• Loss of strength in heat affected zone
• Solidification and liquation cracking
• Fatigue properties.

9. Which of the following processes can be used as alternative technique for joining aluminium and its alloys?
a) Tungsten inert-gas welding
b) Metal inert-gas welding
c) Friction stir welding
d) Oxy-Acetylene flame technique

Answer: c
Clarification: The following alternate techniques are being used for joining of aluminium and its alloys:
• Electron beam welding
• Laser beam welding
• Variable polarity plasma arc welding
• Friction stir welding.

10. Which of the following is not true about friction stir welding?
a) It is a solid state process
b) Fine grained structures can be obtained
c) It eliminates friction welding problems
d) It alters the chemical composition of the workpiece

Answer: d
Clarification: Following are the advantages of friction stir welding:
• It is a solid state process
• Fine grained, re-crystallized microstructures can be obtained
• It eliminates friction welding problems
• There is no significant alteration of chemical composition
• Routinely used to join difficult to friction weld alloys.