Category: Manufacturing Engineering Objective Questions

Manufacturing Engineering Multiple Choice Questions on “Welding Basics-1”.

1. Pinch effect in welding is the result of?
a) Electromagnetic forces
b) Electrostatic forces
c) Magnetic forces
d) Electric forces
Answer: a
Clarification: Pinch effect in welding gives narrow and long flame which is concentrated on the desired part and is achieved by an induction coil, which results in electromagnetic forces.

2. The junction between weld face and base metal is known as?
a) Throat
b) Toe
c) Root
d) Puddle
Answer: b
Clarification: The junction of the weld face and the base metal is known as ‘toe’. For a better weld, the junction should be as small as it can be in size.

3. The junction between two workpieces and weld face is known as?
a) Throat
b) Toe
c) Root
d) Puddle
Answer: a
Clarification: The throat of a weld is the distance from the centre of the face to the root of the weld. Typically, the depth of the throat should be at least as thick as the thickness of the metal we are welding.

4. The portion at which two workpieces are at the nearest distance is called?
a) Throat
b) Toe
c) Root
d) Puddle
Answer: c
Clarification: The weld root is the point at which the back of a weld intersects with the base metal surfaces. It determines the weld penetration and fusion to form a rigid joint.

5. The portion of weld joint that is melted by the heat of melting is called as ______________
a) throat
b) toe
c) root
d) puddle
Answer: d
Clarification: The arc spot or “puddle” weld is started by striking an arc on the deck surface, causing a hole to form in the deck. The weld operation then continues by depositing electrode material on the beam or joist and allowing the molten “puddle” to engage the penetrated deck.

6. Small weld used to temporarily hold the two pieces is called as ______________
a) crater
b) base metal
c) tack weld
d) penetration
Answer: c
Clarification: Tack welds are essentially temporary welds that help to hold two metals in place. The main purpose of the tack weld is to hold the two pieces of metal in place while we apply the actual, final weld.

7. What is the function of a torch?
a) It controls fuel rate
b) It mixes fuel and oxygen and controls delivery
c) It controls oxygen rate
d) It mixes fuel and hydrogen
Answer: b
Clarification: Torch mixes fuel and oxygen and controls delivery. It has two control valves, one for controlling the flow of acetylene and the other of oxygen, entering a chamber called mixing chamber where the two gases are mixed in a correct proportion.

8. The depth up to which, the filler material is mixed up with base metal is called?
a) Deposition
b) Reinforcement
c) Penetration
d) Fusion depth
Answer: c
Clarification: The depth up to which the filler material is mixed up with base metal is called as penetration. Penetration can be increased by increasing temperature and appropriate flux.

9. Weld pass is associated with the movement of __________
a) torch
b) metal
c) flux
d) electrode
Answer: a
Clarification: A single progression of welding or surfacing along a joint or substrate. The result of a pass is a weld bead.

10. The raised potion from the parent metal in welding is known as __________
a) deposition
b) fusion depth
c) penetration
d) reinforcement
Answer: d
Clarification: Weld metal in excess of the quantity required to fill a joint. This can be machined for a good surface finish.

Manufacturing Engineering Multiple Choice Questions on “Moulding sand”.

1. Which of the following is not a principle constituent of molding sand?
a) Silica
b) Aluminum
c) Iron oxide
d) Copper
Answer: d
Clarification: Copper is not a principle constituent of molding sand. Moulding sand is generally composed of silica, aluminum, and iron oxide.

2. When sand is in its natural moist state it is known as?
a) Green sand
b) Facing sand
c) Loam sand
d) Dry sand
Answer: a
Clarification: Green sand is a mixture of silica sand with 18-30% clay, having a water content in the range 6-8%. This name got its name “green” in the sense of “not ready” or “not processed” meaning.

3. Which of the following sand contains clay up to 50% and dries hard?
a) Green sand
b) Facing sand
c) Loam sand
d) Dry sand
Answer: c
Clarification: Loam sand contains clay up to 50% and dries hard. It covers less part of mould. This sand is used for loam sand moulds for making very heavy castings usually with the help of sweeps and skeleton patterns.

4. Which of the following sand is black in color?
a) Green sand
b) Facing sand
c) Loam sand
d) Backing sand
Answer: d
Clarification: Backing sand is black in color due to the presence of coal dust or due to burning. It contains mainly of old, used moulding sand which is black in colour due to the presence of coal dust etc on contact with any hot metal.

5. Which of the following sand is placed next to the surface and comes in contact with the molten metal?
a) Green sand
b) Facing sand
c) Loam sand
d) Backing sand
Answer: b
Clarification: Facing sand is placed next to the surface and meets the molten metal. Facing sand is the sand which covers the pattern all around it. The remaining box is filled with ordinary floor sand.

6. Green strength of sand does not depend upon?
a) Grain size
b) Moisture content
c) Shape and distribution of sand
d) Refractoriness of the sand
Answer: d
Clarification: The strength of the sand in green or moist state is termed as green strength. The green sand particles have the ability to cling to each other to impart sufficient strength to the mold.

7. The strength of the sand which is required to hold the shape of the mould cavity when the metal in the mould is still in liquid form is known as?
a) Hot strength
b) Green strength
c) High strength
d) Refractoriness of the sand
Answer: a
Clarification: When the moisture in sand being eliminated, the sand would reach at a high temperature when the metal in the mold is still in liquid state. The strength of the sand that is required to hold the shape of the cavity is called hot strength.

8. Which of the following will have better plasticity?
a) Coarse sand
b) Fine grained sand
c) Semi grained sand
d) Plasticity does not depend on sand grain size
Answer: b
Clarification: Plasticity is the ability of sand particles to undergo unrecoverable deformation at constant volume without cracking and crumbling. Fine grained sand particles will have better plasticity.

9. The passage of gaseous material, water and steam vapor through the molding sand is known as?
a) Plasticity
b) Flowability
c) Permeability
d) Refractoriness
Answer: c
Clarification: The passage of gaseous material, water and steam vapor through the molding sand is known as permeability. Sand which are coarse or have rounded grains exhibit more permeability. In the absence of adequate permeability, defects like surface blows, gas holes, mold blast etc. may be experienced.

10. Which of the following sand is coated with phenol or urea formaldehyde resins?
a) Shell sand
b) Green sand
c) Dry sand
d) Facing sand
Answer: a
Clarification: Shell sand is coated with phenol or urea formaldehyde resins.

Manufacturing Engineering Multiple Choice Questions on “Fundamentals Of Metal Casting”.

1. ‘V’ or ‘f’ marked surfaces on a casting indicates?
a) Camber allowance
b) Machining allowance
c) Draft allowance
d) Shrinkage allowance
Answer: b
Clarification: Surfaces of castings required to be machined, are made to dimensions more than that indicated on the working drawings. The extra amount of material provided on the surfaces is called machine finish allowance and V or f is indicated on these surfaces.

2. Considering the shrinkage allowance, the amount of pattern, when compared to casting is?
a) larger than casting
b) smaller than casting
c) same as casting
d) equal to casting
Answer: a
Clarification: Shrinkage allowance is a correction for solidification shrinkage of metal and its contraction during cooling. It is larger than the casting to provide space for total contraction.

3. The process of removing unwanted material from the casting is called?
a) fettling
b) cleaning
c) finishing
d) blowing
Answer: a
Clarification: Fettling is the complete process of the cleaning of the casting. It involves removal o the cores, gates, risers, cleaning of the as surface and chipping of any of the unnecessary projection on the surfaces. Core can be removed simply by knocking of it with an iron bar or by means of a cone vibrator. Gates and risers can be removed by hammering, chipping, hack sawing, or by flame or arc cutting.

4. In the following type of foundry, melting unit, as well as balance equipment, are installed to the casting of the particular metal is?
a) jobbing foundry
b) ferrous foundry
c) mass production foundry
d) non-ferrous foundry
Answer: b
Clarification: A jobbing foundry is one that produces a casting or a small number of castings of a given kind as per order. Mass production foundries have automatic molding, pouring and finishing lines with a little or no manual handling. The melting unit, as well as balance equipment in the foundry, is installed in ferrous foundry to suit the casting of particular metal.

5. Which of the following is used for making the hollow cavities in the casting?
a) chaplet
b) vent rod
c) core
d) chill
Answer: c
Clarification: For producing a casting with internal cavities or passages, cores which are made of sand are utilized. Cores are placed in the mold cavity to form the interior surface of the casting and are removed from the finished part during fettling process.

6. What is the limitation of oil as a binder?
a) at lower temperature, bond between sand mix and oil becomes strong
b) at higher temperature, bond between sand mix and oil becomes strong
c) should be added in high volumes
d) quickly hardens
Answer: b
Clarification: At higher temperatures the bond between sand mix and oil becomes hard and brittle there by weakening the sand mix. So, care should be taken about the rate and temperature of baking of oil sands.

7. Cereals are added to the molding sand to improve which of the following?
a) hot strength
b) porosity
c) green strength
d) edge hardness
Answer: c
Clarification: The role of cereals on imparting an amount of green strength in oil sands has been mentioned. Cereals are used because they are less harmful than clays form the point of view of baked strength in oil sand cores. Starch is capable of imparting a higher green strength than dextrin for the same amount of moisture.

8. To improve the surface finish of castings, which of the following additive is used in the molding sand?
a) resins
b) sea coal
c) oils
d) wood flour
Answer: b
Clarification: Resins produces good bonding strength between the sand grains, oils are used as binders, wood flour is cellulose material used to overcome sand expansion defects and seal coal is finely ground soft coal used for surface finish of castings.

9. To permit the escape of gases generated in the mold, which of the following are provided?
a) vent holes
b) chills
c) chaplets
d) core print
Answer: a
Clarification: Chaplets are used to support the cores inside the mold cavity to take care of its own weight and overcome the metallostatic force, core print is used to create openings and various shaped cavities in the castings, and vent hole, a small opening in the mold to facilitate the escape of air and gases.

10. Which of the following is used for making the hollow cavities in the casting?
a) chaplet
b) vent rod
c) core
d) chill
Answer: c
Clarification: Chaplets are used to support the cores inside the mold cavity to take care of its own weight and overcome the metallostatic force, core is a separate part of the mold, made of sand and generally baked, which is used to create openings and various shaped cavities in the castings.

Manufacturing Processes Multiple Choice Questions on “Roll Forming – 1”.

1. Which word best describes the roll forming?
a) Die forming
b) Coining
c) Progressive
d) Profiling
Answer: c
Clarification: Roll forming is a continuous process for forming sheet, strip or coiled metal stock into long shapes of essentially uniform cross-section. The material is fed through pairs of contoured forming rolls, which progressively shape the metal until the desired cross-section is produced.

2. Which of the following are the most desirable materials used in roll forming?
a) Spring steel
b) Chromium-molybdenum steel
c) Non-metals
d) Mild steels and aluminium
Answer: d
Clarification: Both ferrous and non-ferrous metals as well as some non-metallic material can be roll formed. Mild steel and aluminium are the most common materials used in the process. Additionally, polished, painted, coated and plated materials can also be roll formed.

3. The most common cutting method of roll forming is ____________
a) sawing
b) pre-cutting
c) parting
d) post-cutting
Answer: d
Clarification: The stock to be roll formed may be either pre-cut to a pre-determined length before roll forming, or post-cut afterward to a specified dimension. But the latter one is the most common. By incorporating auxiliary equipment such as pre-notching, punching, embossing, etc. the post-cut method can be a complete net-shape process, fully automated.

4. Pre-cut roll forming production speed are ______________
a) 600 to 800 feet per minute
b) up to 1000 feet per minute
c) 50 to 250 feet per minute
d) 100 to 300 feet per minute
Answer: c
Clarification: In the pre-cut method, material passes through the rolls at fixed speeds of 50 to 250 feet per minute or 15 to 76 meters per minute. Pre-cut roll forming is commonly used for low production when nothing is required that cannot be easily done using post-cut lines, or when multiple profile s require expensive and or time consuming tool changeover.

5. Post-cut roll forming production speeds are ______________
a) 100 to 180 feet per minute
b) 650 to 780 feet per minute
c) 800 to 900 feet per minute
d) up to 100 feet per minute
Answer: a
Clarification: The post-cut method typically involves a stock uncoiler, a roll forming machine, and a runout table. Production speeds average 100 to 180 feet, or 30 to 55 meters per minute, but can be as high as 600 feet or 185 meters per minute.

6. Camber refers to deviation from a straight line the____
a) side edge before roll forming
b) vertical plane
c) horizontal plane
d) side edge after roll forming
Answer: a
Clarification: Depending on the length, roll forming length tolerance of plus or minus 0.020 to 0.093 of an inch, or 0.51 to 0.236 of a millimetre are possible. To determine the straightness few terms are used and camber being one of them. Camber means the deviation a side edge from a straight line measured prior to roll forming.

7. When does springback occur?
a) When the material does not stress beyond its elastic limit
b) When the material is stressed beyond its elastic limit
c) When the material is too hard
d) When the material is too soft
Answer: a
Clarification: Elastic limit is the point beyond which material deforms permanently under stress. Springback is the tendency to regain the initial shape. Therefore, it occurs when the material does not stress beyond its elastic limit during forming. Spring is often compensated by overforming the material and then allowing it to ‘spring back’ to the required profile.

8. The flower design is____
a) the total number of formed bends
b) a station-by-station overlay of progressive part contours
c) the part’s finished profile
d) the finished profile divided into component bends and straight sections
Answer: b
Clarification: The design of forming rollers is dependent on several factors such as number of forming passes, material , roll material, flower design, etc. Flower design is a station-by station overlay of the progressive part contours starting with the flat strip before forming and ending with the final desired section profile.

9. Which of the following is the most common material used to produce forming rolls?
a) Aluminium
b) Carbide
c) Chrome steels
d) Oil hardened tool steels
Answer: d
Clarification: Several types of materials are used in the manufacture of the forming rolls and oil hardened tool steel being the most common. For extended tool life, hardened high-carbon, high-chromium too steels are used. On extremely tough forming applications involving high temperatures and or abrasive materials, aluminium/bronze or carbide rolls are required.

10. Why spacers are used in roll forming machines?
a) To prevent the springback of the material
b) To fix the rolls in exact position
c) To accommodate specific material thickness by adjusting the
d) To support the shaft
Answer: b
Clarification: Spacers are used to fix the rolls in the exact position on the spindles. Vertical adjustment of the top shaft fine tunes the machine to accommodate specific rolls and material thickness.

Manufacturing Processes Multiple Choice Questions on “Electrochemical Etching – 7”.

1. Morphology of μpSi and mpSi can be defined by a concrete spatial distribution.
a) True
b) False
Answer: b
Clarification: The sponge-like morphology of μpSi and mpSi cannot be defined by a concrete spatial distribution because of the complex structure of their porous network.

2. The resulting pore structure in pSi is intrinsically dependent on the doping level of the Si wafer.
a) True
b) False
Answer: a
Clarification: MpSi is produced by electrochemical etching of n-type wafers. The etching of p- and n-type Si wafers with a high or moderate level of doping yields mpSi structures and μpSi structures.

3. Why the pore characteristics of the resulting pSi structures depend upon the doping type? Choose the most correct option.
a) Processing time depends on doping
b) The manufacturing process is selected on the basis of doping
c) The pore formation mechanism relies on doping
d) Atomic size of doping atom affects the final structure
Answer: c
Clarification: The reason why the pore characteristics of the resulting pSi structures depend upon the doping type and its level of the silicon wafer is that the pore formation mechanism relies on these parameters.

4. _____ mechanism is associated with the pore formation in μpSi structures.
a) Enhanced electric field
b) Tunnelling
c) Quantum confinement
d) Space-charge limited mechanism
Answer: d
Clarification: The space-charge limited mechanism is associated with the pore formation in μpSi structures, which results when n-type silicon wafers are electrochemically etched in HF solutions.

5. The enhanced electric field and tunnelling mechanisms are associated with the formation of _____ structures.
a) mpSi
b) MpSi
c) μpSi
d) pSi
Answer: a
Clarification: The enhanced electric field and tunnelling mechanisms are associated with the formation of mpSi structures when highly or moderately doped Si wafers are electrochemically etched in HF solutions.

6. In the pore formation mechanism of MpSi, electronic holes initiate the dissolution process of silicon.
a) True
b) False
Answer: a
Clarification: As far as the pore formation mechanism of MpSi is concerned, electronic holes initiate the dissolution process of silicon and these are minority charge carriers in n-type silicon. Therefore, the concentration of electronic holes in n-type silicon under equilibrium conditions is very low.

7. The neutral state is achieved when the concentration of electrons is equal to the concentration of electronic holes and ionized donors.
a) True
b) False
Answer: a
Clarification: Three types of charges are present in the bulk silicon: namely, electronic holes, electrons and ionized donors. The system is a neutral state when the concentration of electrons is equal to the concentration of electronic holes and ionized donors together.

8. For a given level of doping, the growth of MpSi in n-type silicon substrates can be controlled by_____
a) amount of electric current passed
b) current density
c) voltage drop
d) processing time
Answer: b
Clarification: For a given level of doping, the growth of MpSi in n-type silicon substrates can be led by the current density and the illumination applied in the course of the etching process.

9. A pre-treatment by a lithographic patterning stage enables the production of ordered pore distribution.
a) True
b) False
Answer: a
Clarification: As-produced MpSi has a random pore distribution since pores nucleate uniformly on the Si wafer surface. A pre-treatment by a lithographic patterning stage enables the production of MpSi structures with perfectly ordered pores featuring square or triangular arrangement.

10. Among all the etching parameters, the etching current density (J) is the most critical factor.
a) True
b) False
Answer: a
Clarification: The growth of well-defined cylindrical macropores from top to bottom in MpSi can be precisely controlled through the etching parameters (e.g. etching current density, HF concentration and its temperature, wafer doping, illumination intensity, etc.). In particular, among these parameters, the etching current density (J) is a critical factor to lead a homogeneous pore growth as the longer the pore the more effective the collection of photo-generated holes.

Manufacturing Processes Multiple Choice Questions on “Abrasive Jet Micromachining – 3”.

1. In AJMM, material removal starts when the fracture strength is reached.
a) True
b) False
Answer: a
Clarification: During AJMM, plastically deformed surface layer is formed near the eroded surface, and therefore, the yield strength of the material increases. Upon further deformation, the yield strength at the surface of the material will eventually become equal to its fracture strength. The surface becomes brittle and its fragments may be removed by subsequent impacts.

2. Brittle fracture can occur due to indentation rupture.
a) True
b) False
Answer: a
Clarification: Brittle fracture may take place due to:
1) Indentation ruptures
2) Elastic–plastic deformation
3) Critical plastic strain theory
4) Radial cracking and propagation or surface energy criterion.

3. The mass loss of workpiece is proportional to_____
a) power supplied
b) nozzle diameter
c) amount of abrasive
d) carrier gas
Answer: c
Clarification: The mass loss of workpiece is proportional to the amount of abrasive.
Mass loss = (Kρmv²)/(2H), where, K (> 2) is a dimensionless factor, m and v amount and velocity of
particles, and ρ and H are density and hardness of the eroded material, respectively. The above relation is true for brittle erosion but not for softer materials (elastomers and some metals) due to time variant erosion behaviour.

4. In AJMM, there is initial weight gain in the workpiece.
a) True
b) False
Answer: a
Clarification: Especially at normal impact angle, particles tend to embed in the material, resulting in an initial gain in weight of the specimen. After this incubation time steady-state erosion is established and mass loss from the eroded material is proportional to the amount of abrasive particles.

5. Erosion rate is directly proportional to velocity of the jet.
a) True
b) False
Answer: a
Clarification: The principal empirical relation between erosion rate Erate, expressed as the quotient of mass loss and amount of abrasive, and particle velocity is given as a power function by
E_rate α v^k , where k= velocity coefficient.

6. For metal, velocity coefficient ranges from_____
a) 0.5—1
b) 1.8—3
c) 2.3—3
d) 2—4
Answer: c
Clarification: velocity coefficient k commonly reported for,
1) for metals – between 2.3 and 3,
2) for glasses – between 2 and 4 and
3) for elastomers – between 1.8 and 3.2.

7. AJMM can also machine poly methyl methacrylate (PMMA).
a) True
b) False
Answer: a
Clarification: AJMM can machine much steeper side walls and flatter bottom section in PMMA than those in glass. For PMMA, there is only a small probability of a particle rebounding from the steep side wall and hitting the opposite side.

8. There is appearance of the dimples during AJM.
a) True
b) False
Answer: a
Clarification: Appearance of the dimples during AJM for 10s. for various machining sets of abrasives and ceramic materials. Properties of the dimples do not differ in terms of the removed volume, but also the roughness of the struck face for different combination of abrasive particles and workpiece material.

9. In AJMM, the substrate has to be shielded by a mask.
a) True
b) False
Answer: a
Clarification: In AJMM, the substrate has to be shielded by a wear resistant mask that is patterned with the desired contour. The mask determines the accuracy of the dimensions in the plane of the desired structure.

10. During blasting, the workpiece is exposed to an abrasive air jet pressure of _____ MPa.
a) 0—1
b) 0—0.2
c) 0.2—0.8
d) >1
Answer: c
Clarification: During blasting, the workpiece is exposed to an abrasive air jet pressure of 0.2-0.8 MPa and abrasive particles average diameter of 10-100 μm. The scan strategy and the particle beam profile of the nozzle are of great importance.