Category: Manufacturing Engineering Objective Questions

Manufacturing Engineering Multiple Choice Questions on “Welding Metallurgy and Welding Defects”.

1. Which of the following defects occur due to flux employed and electrode coating?
a) Inclusion of slag
b) Inadequate penetration
c) Incomplete fusion
d) Porosity
Answer: a
Clarification: Slag inclusions are one of the main weld defects. If we don’t properly clean the slag from a bead, we run the risk of it becoming part of the weld when we run the next bead. A good welder will generally burn it out on the next pass, but if not, there will be a chunk of slag in the bead which leaves a weak spot. Slag inclusions.

2. Which of the following defects occur when the deposited metal is not focused on the root of weld?
a) Inclusion of slag
b) Inadequate penetration
c) Incomplete fusion
d) Porosity
Answer: b
Clarification: Inadequate penetration defects occur when the deposited metal is not focused at the root of weld. Some part of gap remains unwelded due to this defect.

3. Which of the following defects occur when weld metal layer fails to fuse together?
a) Inclusion of slag
b) Inadequate penetration
c) Incomplete fusion
d) Porosity
Answer: c
Clarification: Incomplete fusion defects occur when weld metal layer fails to fuse together. It causes discontinuity in weld zone.

4. Which of the following defects occur due to the entrapment of gas bubbles by the freezing dendrites during the cooling of molten pad?
a) Inclusion of slag
b) Inadequate penetration
c) Incomplete fusion
d) Porosity
Answer: d
Clarification: Referred to as worm holes, these are gas pockets trapped in the weld. A couple of reasons would be from not enough shielding gas in MIG, or moisture in the flux.

5. Which of the following defects occur due to filler material having a different rate of contraction compared to parent metal?
a) Undercut
b) Spatter
c) Cracking in weld metal
d) Cold cracking
Answer: c
Clarification: Weld cracking occurs close to the time of fabrication. Most forms of cracking result from the shrinkage strains that occur as the weld metal cools. It can be of hot cracks types.

6. Which of the following defects occur due to melting or burning away of base metal?
a) Undercut
b) Spatter
c) Cracking in weld metal
d) Cold cracking
Answer: a
Clarification: Undercut is the cardinal sin of welding grasshopper! Cutting into the steel with the force of the arc leaves a cut out groove in the weld. If this is not filled back in with filler metal, it leaves a weld defect which is a weak point that can cause the joint to fail. This can cause property damage, injury and even loss of life.

7. Which of the following defects occur due to scattering of metal around the vicinity of weld?
a) Undercut
b) Spatter
c) Cracking in weld metal
d) Cold cracking
Answer: b
Clarification: Spatters are the droplets of molten material during GAS welding or arc welding. A temperature difference and slag accumulation are the reason of spatter formation. Welding speed is also one of the main causes of spatter. Type of material used and type of welding also decide to spatter density.

8. Which of the following defects occur due to incorrect welding techniques?
a) Undercut
b) Hot cracking
c) Cracking in weld metal
d) Cold cracking
Answer: c
Clarification: Cracking in weld metal defect occur due to incorrect welding techniques. Sometimes cracking may not be visible by naked eyes.

9. Which of the following defect is influenced by sulphur and carbon content of weld metals?
a) Undercut
b) Hot cracking
c) Cracking in weld metal
d) Cold cracking
Answer: b
Clarification: Hot cracks are those that occur at elevated temperatures and are usually solidification related. It is being influenced by sulphur and carbon content of weld metals. Sometimes cracking may not be visible by naked eyes.

10. Which of the following defects occur at a lower temperature?
a) Undercut
b) Hot cracking
c) Cracking in weld metal
d) Cold cracking
Answer: d
Clarification: Cold cracks are those that occur after the weld metal has cooled to room temperature and may be hydrogen related. These occurs are lower temperature. Sometimes cracking may not be visible by naked eyes.

Manufacturing Engineering Multiple Choice Questions on “Expendable Mold, Permanent-Pattern Processes”.

1. Applications of sand casting include __________
a) machine bases
b) large turbine impellers
c) propellers
d) automobile gears
Answer: d
Clarification: Typical applications of sand casting include machine bases, large turbine impellers, propellers, plumbing fixtures, and a wide variety of other products and components.

2. Sand casting consists of __________
a) placing a pattern in sand to make an imprint
b) incorporating a gating system
c) removing the pattern and filling the mold cavity with molten metal
d) all of the mentioned
Answer: d
Clarification: Basically, sand casting consists of
a) placing a pattern (having the shape of the desired casting) in sand to make an imprint,
b) incorporating a gating system,
c) removing the pattern and filling the mold cavity with molten metal,
d) allowing the metal to cool until it solidifies,
e) breaking away the sand mold, and
f) removing the casting.

3. Which of the following are used to mold the sand mixture into shape of the casting and may be made of wood, plastic, metal?
a) Vents
b) Patterns
c) Cores
d) Chills
Answer: b
Clarification: Patterns are used to mold the sand mixture into the shape of the casting and may be made of wood, plastic, or metal. The selection of a pattern material depends on the size and shape of the casting, the dimensional accuracy and the quantity of castings required, and the molding process.

4. Which of the following fill the flask uniformly with sand under a high-pressure stream?
a) Sandslingers
b) Patterns
c) Cores
d) Chills
Answer: a
Clarification: A sand slinger is an automatic machine equipped with a unit that throws sand rapidly and with great force into the mould box. Sand slingers fill the flask uniformly with sand under a high-pressure stream, they are used to fill large flasks and are operated typically by machine.

5. In which of the following technique, sand is compacted by a controlled explosion or instantaneous release of compressed gases?
a) vacuum molding
b) impact molding
c) blow molding
d) rotational molding
Answer: b
Clarification: In impact molding, the sand is compacted by a controlled explosion or instantaneous release of compressed gases whine in vacuum molding the pattern is covered tightly with a thin sheet of plastic.

6. In which of the following technique, the pattern is covered tightly with a thin sheet of plastic?
a) vacuum molding
b) impact molding
c) blow molding
d) rotational molding
Answer: a
Clarification: In vacuum molding (also known as the V process), the pattern is covered tightly with a thin sheet of plastic while in impact molding, the sand is compacted by a controlled explosion or instantaneous release of compressed gases.

7. Shell-molding applications include ____________
a) small mechanical parts requiring high precision
b) such as gear housings
c) cylinder heads
d) all of the mentioned
Answer: d
Clarification: Shell-molding applications include small mechanical parts requiring high precision, such as gear housings, cylinder heads, and connecting rods. The process also is used widely in producing high-precision molding cores.

8. Along with plaster of paris, with the addition of tale, which of the following is added in the plaster-molding process?
a) copper
b) iron
c) silica
d) calcium
Answer: c
Clarification: In the plaster-molding process, the mold is made of plaster of paris (gypsum or calcium sulphate) with the addition of tale and silica flour to improve strength and to control the time required for the plaster to set.

9. Typical parts such as impellers, cutters for machining operations are made by?
a) plaster-molding process
b) ceramic-mold casting process
c) shell-molding
d) metallic-mold casting process
Answer: b
Clarification: Typical parts made are impellers, cutters for machining operations, dies for metalworking, and molds for making plastic and rubber Components. Parts weighing as much as 700 kg have been cast by this process.

10. The surface finish in a plaster-molding process is?
a) rough
b) good
c) slippery
d) bad
Answer: b
Clarification: In the plaster-molding process, castings have a good surface finish with fine details. Because plaster molds have lower thermal conductivity than other mold materials, the castings cool slowly, and thus a more uniform grain structure is obtained with less warpage.

Manufacturing Engineering Multiple Choice Questions on “Jigs and Fixtures”.

1. With the use of Jigs and fixture total cost of production
a) Increases
b) Decreases
c) Remains same
d) Jigs are not used in any production process
Answer: b
Clarification: Total cost of production decreases with the use of jigs and fixture. Jigs are holding device and fixture are generally used for the bigger work piece.

2. With the use of Jigs and fixture rate of production will
a) Increase
b) Decrease
c) Remains same
d) Jigs are not used in any production process
Answer: a
Clarification: Total production increase with the use of jigs and fixture. Jigs are holding device and fixture are generally used for the bigger work piece.

3. Jigs and fixture increases the accuracy of the parts.
a) True
b) False
Answer: a
Clarification: Accuracy of parts increases by use of jigs and fixture. Jigs are holding device and fixture are generally used for the bigger work piece.

4. Jigs And fixture are used to provide interchangeability.
a) True
b) False
Answer: a
Clarification: Interchangeability of parts increases by use of jigs and fixture. Jigs are holding device and fixture are generally used for the bigger work piece.

5. With the use of Jigs and fixture quality control expenses will
a) Reduce
b) Increases
c) Jigs and fixture are not used in any production process
d) None of the mentioned
Answer: a
Clarification: Jigs and fixture increase accuracy. Jigs are holding device and fixture are generally used for bigger work piece. Interchangeability of parts increases by use of jigs and fixture.

6. With the use of Jigs and fixture
a) Labour cost decreases
b) Labour cost increases
c) Labour cost decreases
d) None of the mentioned
Answer: a
Clarification: Less skilled labour required. Interchangeability of parts increases by use of jigs and fixture. Jigs and fixture increases accuracy. Jigs are holding device and fixture are generally used for bigger work piece.

7. Which of the following is not correct about fixture?
a) It is used to hold the work
b) It is used to position the work the work
c) It assures high accuracy of parts
d) It is used to guide the cutting tool
Answer: d
Clarification: Fixture do not guide cutting tool. jigs and fixture increases accuracy. Jigs are holding device and fixture are generally used for bigger work piece.

8. Which of the following is not correct about jig?
a) It is used to hold the work
b) It is used to position the work the work
c) It is used to guide the cutting tool
d) None of the mentioned
Answer: d
Clarification: All of the mentioned are correct about jigs. Jigs and fixture increases accuracy. Jigs are holding device and fixture are generally used for bigger work piece.

9. In which of the following operation jigs are preferred over fixture?
a) Drilling
b) Turning
c) Milling
d) Grinding
Answer: a
Clarification: Jigs and fixture increases accuracy. Jigs are holding device and fixture are generally used for bigger work piece. Jigs are preferred over fixture in drilling because they also help in guidance of tool.

10. Number of degree of freedom of a workpiece in space is equal to
a) 10
b) 12
c) 14
d) 16
Answer: b
Clarification: Work piece has 16 degree of freedom. It can have 16 different movements.

Manufacturing Processes Multiple Choice Questions on “Electro-Chemical Machining – 1”.

1. Electro-chemical machining is opposite of electrochemical coating.
a) True
b) False
Answer: a
Clarification: In electrochemical or galvanic coating, some another material is coated on the workpiece metal; whereas in Electro-chemical machining, material is removed from the workpiece.

2. ECM can also be called as un-controlled anodic dissolution.
a) True
b) False
Answer: b
Clarification: ECM can be thought of a controlled anodic dissolution at atomic level of the workpiece that is electrically conductive by a shaped tool due to flow of high current at relatively low potential difference through an electrolyte which is quite often water based neutral salt solution.

3. For ECM of steel which is used as the electrolyte?
a) Kerosene
b) NaCl
c) Deionised water
d) HNO₃
Answer: b
Clarification: During ECM, there will be reactions occurring at the electrodes i.e. at the anode or workpiece and at the cathode or the tool along with within the electrolyte. For electrochemical machining of steel, generally a neutral salt solution of sodium chloride (NaCl) is taken as the electrolyte.

4. MRR is ECM depends on _____________
a) hardness of work material
b) atomic weight of work material
c) thermal conductivity of work material
d) ductility of work material
Answer: b
Clarification: In ECM, material removal takes place due to an atomic dissolution of work material. Electrochemical dissolution is governed by Faraday’s laws. Also, for ECM, MRR= IA/(Fρv), where I= current, ρ= density of the material, A= atomic weight, v= valency, F= faraday’s constant.

5. For which of the following ECM cannot be undertaken?
a) Steel
b) Nickel based superalloy
c) Aluminium oxide
d) Titanium alloy
Answer: c
Clarification: ECM can machine any electrically conductive work material irrespective of their hardness, strength or even thermal properties. In ECM, material is removed from the workpiece by oxidizing it. Aluminium oxide cannot be oxidized further; therefore it cannot be machined by ECM.

6. Commercial ECM is carried out at a combination of ___________
a) low voltage high current
b) low current low voltage
c) high current high voltage
d) high voltage only
Answer: a
Clarification: As we know, in ECM, MRR= IA/(Fρv), where I= current. Therefore, the amount of electrochemical dissolution or deposition is proportional to the amount of charge passed through the electrochemical cell, i.e.
m∝Q, where m = mass of material dissolved or deposited
Q = amount of charge passed.

7. In ECM of pure iron a material removal rate of 600 mm3/min is required. What will be the current requirement?
a) 157A
b) 183.6A
c) 247.8A
d) 268.8A
Answer: d
Clarification: MRR= IA/(Fρv)
MRR = 600 mm³/min = 600/60 mm³/s = 10 mm³/s = 10×10^-3cc/s
A= 56,
v= 2,
F= 96500 coulomb, and
ρ = 7.8 gm/cc
Therefore, I= (96500*10*10^-3*7.8*2)/56
I= 268.8A.

8. In ECM operation of pure iron an equilibrium gap (h) of 2 mm is to be kept. What will be the supply voltage (v), if the total overvoltage is 2.5 Volts. The resistivity(r) of the electrolyte is 50 Ω-mm and the set feed rate (f) is 0.25 mm/min.
a) 5v
b) 7.8v
c) 11.3v
d) 13.2v
Answer: d
Clarification: h= c/f
Where, c= (v- overvoltage)*A/(F*ρ*r*v)
Therefore, c= (v-2.5)*56/(96500*7.8*10^-3*50*2)
c= (v-2.5)/1344.1
Now, h= c/f
2= [(v-2.5)/1344.1]/[0.25/60]
Therefore, v= 13.2 volts.

9. In ECM, workpiece acts as a cathode.
a) True
b) False
Answer: a
Clarification: In ECM, material is depleted from anode workpiece and transported to a cathode tool in an electrolyte bath. Electrolyte flows rapidly between two poles to carry off depleted material, so it does not plate onto tool.

10. Electrolyte used in ECM should have _____________
a) high specific heat
b) lower resistance to film formation on the workpiece
c) higher viscosity
d) corrosive nature
Answer: a
Clarification: Desirable properties of the electrolytes are as follows:
• High electrical conductivity – for easy ionization
• Low viscosity – for easy flow
• High specific heat – to carry more heat
• Chemical stability – to be chemically neutral or
does not disintegrate during the reaction
• Resistance to formation of passivating film on
the workpiece surface
• Non corrosiveness and non-toxicity
• Inexpensiveness and easy availability.

Manufacturing Processes online quiz on “Abrasive Jet Micromachining – 9”.

1. Which of the following technology is used for ferrite substrates?
a) Powder coating
b) Powder blasting
c) Sintering
d) Continuous powder processing
Answer: b
Clarification: Another possible application of the powder blasting technology is the micro-structuring of ferrite substrates. In this case, powder blasting proved to be not only the most appropriate but also a very fast and cheaper way to get such structures.

2. Manufacturing of capillary electrophoresis chips has an application of which of the following process?
a) Ultrasonic machining
b) Chemical Milling
c) Abrasive jet machining
d) Electron beam machining
Answer: c
Clarification: The device consists of a glass chip which contains a single separation channel as well as an integrated conductivity detection cell. In contrast to most micro-fluidic glass devices, the channels are not wet etched in HF but machined by AJMM which allows the creation of micro-structures below 100μm, and additionally makes parallel holes machining at very low costs outside the clean room environment.

3. Monolithic suspended micro-structure in glass was realized using _____
a) oblique AJMM
b) ion beam technique
c) photo chemical technique
d) laser beam technique
Answer: a
Clarification: Complex three-dimensional and monolithic suspended microstructure in glass was realized using normal and oblique AJMM. By controlling the under etching induced by oblique AJMM blasting, millimetrer high microstructure single as scan be fabricated with an aspect ratio of 5:10, as well as free-standing monolithic 100-μm-wide structures, suspended over many millimeters.

4. The mask using SU8, _____ is applied as a micro-pattern for AJMM process.
a) SU6
b) SU7
c) SU8
d) SU9
Answer: c
Clarification: A passive micro-mixer with3-dimensional feature fabricated by AJMM process by employing photo-polymer as a mask on a glass slide target. The mask using SU8, a photo-sensitive polymer is applied as a micro-pattern for AJMM process. The fabrication process involved three glass target slides and conducted multi-masking processes with four different mask patterns.

5. Which of the following is true about AJMM?
a) It is a high maintenance process
b) It is a time consuming process
c) Depths upto few microns are not possible
d) Multiple features can be machined in one operation
Answer: d
Clarification: Following are the few advantages of AJMM;
• Minimal tooling cost
• Quick turn-around for prototyping and development work
• Feature sizes down to 100 μm and featured depths to just a few microns are possible
• Multiple features can be machined in one operation.

6. AJMM generates no heat.
a) True
b) False
Answer: a
Clarification: Following are the few advantages of AJMM;
• The process generates no heat and does not change the material properties of the work-piece
• Very high pattern densities are possible
• Process works well with metalized parts
• Features can be of any 2D shape: square, round, designed shapes, and connected channels.

7. Abrasive jet machined features have tapered sidewalls ranging from _____
a) 5—10˚
b) 22—28˚
c) 15—30˚
d) 18—26˚
Answer: d
Clarification: Unlike vertical side walls produced by ultrasonic machining, abrasive blasting machined features have tapered sidewalls ranging from 18 to 26˚, depending on several factors.

8. Maximum possible aspect ratio in AJMM is_____
a) 1:2
b) 1.5:3
c) 2:1
d) 3:1
Answer: d
Clarification: In AJMM, maximum aspect ratio is 3:1 (Thickness: Diameter). Therefore, its applications are restricted to brittle materials because of low MRR in case of ductile materials.

9. Which of the following is correct about AJMM?
a) It requires no cleaning
b) It has very high accuracy
c) It tends to pollute the environment
d) The nozzle has very less wear
Answer: c
Clarification: Following are the limitations of AJMM;
• Sometimes additional cleaning operation is required to machine parts to remove abrasives from the surface
• Machining accuracy is poor
• Nozzle wear rate is high
• The process tends to pollute the environment.

10. Dimensional tolerances of very less microns are possible with AJMM
a) True
b) False
Answer: a
Clarification: With AJMM, feature location and dimensional tolerances down to +/-25 microns are possible. Also, features of any 2D shape: square, round, designed shapes, and connected channels can be machined.

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