Category: Manufacturing Engineering Objective Questions

Manufacturing Processes Multiple Choice Questions on “Abrasive Jet Micromachining – 5”.

1. Elastomer masks are provided in the form of foils.
a) True
b) False
Answer: a
Clarification: These types of mask usually provided in the form of ready-made foil with self-adhesive properties. Besides, elastomers can show ductile, elastic and brittle behaviour and experiments have to be carried out under relevant practical conditions.

2. Photo-resists are _____ materials.
a) photogenic
b) photosensitive
c) photo-dissociate
d) photo-emissive
Answer: b
Clarification: Photo-resists are photo-sensitive materials. There are two types of photo-resists; positive and negative. The major drawback is that it needs Expensive equipment to prepare the mask.

3. Positive resists are formed when resist is exposed to UV light.
a) True
b) False
Answer: a
Clarification: For positive resists, the resist is exposed with UV light wherever the underlying material is to be removed. In these resists, exposure to the UV light changes the chemical structure of the resist so that it becomes more soluble in the developer.

4. After treatment with UV light, resist is washed away by the developer solution.
a) True
b) False
Answer: a
Clarification: The exposed resist, after UV treatment is washed away by the developer solution, leaving windows of the bare underlying material. In other words, “whatever shows, goes.” The mask, therefore, contains an exact copy of the pattern which is to remain on the wafer.

5. SU-8 is most commonly used negative resist.
a) True
b) False
Answer: a
Clarification: Negative resists behave in just the opposite manner as that of the positive resists. Epoxy-based SU-8 is one of the good negative resists. It is able to provide features with high aspect ratios (>10) with UV-lithography.

6. Structures with high aspect ratios are possible with _____
a) photo-resist material
b) metals
c) elastomers
d) porous silicon
Answer: b
Clarification: Stainless steel masks are very suitable for high particle velocities and fast machining operations. Structures with high aspect ratios are achievable due to the low erosion rate of steel. Attention has been paid to the adhesive layer, which should not only stick the two materials together but also avoid under etching.

7. Feature is the major drawback of metal masks.
a) True
b) False
Answer: a
Clarification: The limiting factors for all metal masks are the feature and the structuring procedure where no free-standing contours are possible. Metal masks should be applied preferably for medium and large sizes.

8. Elastomers are suitable for high air pressures.
a) True
b) False
Answer: a
Clarification: Elastomer foils are easy to pattern and allow a high complexity of the design but the procedure is somewhat time consuming. They are not suitable for high air pressures due to their elastic deformation behaviour.

9. At higher particle velocities, adhesion between the mask and the workpiece material becomes weak.
a) True
b) False
Answer: a
Clarification: The adhesion is significantly weaker for complex patterns and higher particle velocities that may cause a release of the foils from the substrate. Their applicability is limited to single workpieces and feature sizes down to 75μm.

10. High aspect ratios are not possible with SU-8 material.
a) True
b) False
Answer: a
Clarification: A good compromise in terms of feature size and imaging accuracy gives the epoxy based photo-resist SU-8. Since the maximum thickness of an SU-8 layer is about 300μm, no high aspect ratio is achievable and its application is limited to shallow cavities.

Manufacturing Processes Multiple Choice Questions on “Friction Welding – 3”.

1. In friction welding process, materials are joined by _____ motion between materials.
a) rectilinear
b) rubbing
c) translatory
d) brownian
Answer: b
Clarification: Friction welding is a solid-state joining process that produces coalescence in materials, using the heat developed between surfaces through a combination of mechanically induced rubbing motion and applied load. The resulting joint is of forged quality.

2. All metallic engineering materials which are _____ can be friction welded.
a) soft
b) weldable
c) forgeable
d) metamaterials
Answer: c
Clarification: As a rule, all metallic engineering materials which are forgeable can be friction welded, including automotive valve alloys, maraging steel, tool steel, alloy steels and tantalum. In addition, many castings, powder metals and metal matrix composites are weldable.

3. Friction welding is _____ process.
a) costly
b) cost saving
c) time consuming
d) highly material selective
Answer: b
Clarification: Since dissimilar materials can be joined, a significant cost savings are possible because engineers can design bimetallic parts that use expensive materials only where needed. Expensive forgings and castings can be replaced with less expensive forgings welded to bar stock, tubes, plates and the like.

4. Friction welding produces quality joints, with a 100% _____ weld.
a) lap joint
b) tee-joint
c) butt joint
d) edge joint
Answer: c
Clarification: Friction welding produces forged quality joints, with a 100% butt joint weld through the contact area. Furthermore, in friction welding heat affected zone is much narrower as compared to other welds, which indeed reduces the cost of post-weld heat treatments (stress relieving processes).

5. Which of the following is not true about friction welding?
a) Dissimilar metals cannot be joined
b) This technique is relatively faster as compared to the other techniques
c) This technique is suitable for any parts of shape or size
d) Sheared surfaces can also be joined by the process
Answer: a
Clarification: Following are the few advantages of friction welding over other techniques:
• Dissimilar metals are joined, even some considered incompatible or unweldable.
• The process is at least twice— and up to 100 times—as fast as other welding techniques.
• Friction welders are versatile enough to join a wide range of part shapes, materials and sizes.
• Joint preparation isn’t critical… machined saw cut, and even sheared surfaces are weldable.

6. Which of the following holds true for friction welding?
a) Hazardous fumes are generated during the process
b) Argon is used as a shielding gas
c) It is a power consuming process
d) There are no solidification defects in the welded parts
Answer: d
Clarification: Following are the few reasons to consider friction welding over other techniques:
• The machine-controlled process eliminates human error, and weld quality is independent of operator skill.
• It’s ecologically clean—no objectionable smoke, fumes, or gases are generated that need to be exhausted.
• No consumables are required— no flux, filler material, or shielding gases.
• Power requirements are as low as 20% of that required of conventional welding processes.
• Since there is no melting, no solidification defects occur, e.g. gas porosity, segregation or slag inclusions.

7. In inertia friction welding ______ energy of welding machine is used.
a) electrical
b) potential
c) rotational
d) frictional
Answer: c
Clarification: Inertia Friction Welding is a variation of friction welding in which the energy required to make the weld is supplied primarily by the stored rotational kinetic energy of the welding machine.

8. In inertia friction welding, one workpiece is connected to _____
a) flywheel
b) the pin tool
c) rotor
d) generator
Answer: a
Clarification: In Inertia Welding, one of the workpieces is connected to a flywheel and the other is restrained from rotating. The flywheel is accelerated to a predetermined rotational speed, storing the required energy. The drive motor is disengaged and workpieces are forced together by the friction welding force.

9. Weld strength in inertia friction welding is more than direct drive friction welding.
a) True
b) False
Answer: a
Clarification: Inertia Friction Welding has the following advantages over the Direct Drive Friction Welding process:
• Helical flow lines and hot working at end of weld cycle can help in weld strength
• Ease of monitoring, given only two variables for welding: energy (RPM) and pressure. Energy can be monitored before a signal is given to weld reducing the variables during welding to one
• Weld torque is measured indirectly by measuring the rate of spindle speed change.

10. In direct drive friction welding, lower weld forces are generated.
a) True
b) False
Answer: a
Clarification: Following are the advantages of direct drive friction welding over inertia friction welding:
• Lower weld force for solid parts. Larger parts can be welded on same tonnage machine
• Lower weld torque if brake is applied at end of weld cycle. Tooling requirements are, therefore, less rigid
• Lower RPM for solid parts
• No flywheel change between setups.

Manufacturing Processes Multiple Choice Questions on “Wire-cut EDM – 8”.

1. Submerged machining is extremely useful for applications that generally have_____
a) poor flushing conditions
b) intricate shapes
c) tapered sections
d) good weldability
Answer: a
Clarification: Submerged machining is extremely useful for applications that generally have poor flushing conditions. Applications where poor flushing conditions exist are numerous.

2. Submerged machining is used for ____
a) cutting small taper angles
b) tiny workpieces
c) laminations
d) workpieces with no undercuts
Answer: c
Clarification: Some applications and examples where submerged machining is more practical would be cutting large taper angles, tall workpieces, laminations, tubes, irregular shaped parts, workpieces with undercuts and cutting very close to the edge of the workpiece.

3. There is a greater risk of breaking a wire if ______
a) temperature of the wire is too high
b) larger taper angles are to be cut
c) the flush is not set properly
d) there is an inadequate flow of di-electric fluid
Answer: c
Clarification: There is a greater risk of breaking a wire if the flush is not set properly or if too much power is used. This condition is greatly reduced when cutting the part submerged.

4. How many of the following processes does not need submerged machining capabilities?
– starting a cut from the edge of a workpiece
-slicing a tube
-slicing a bar stock
-starting a cut from a large diameter start hole.
a) 1
b) 2
c) 3
d) 4
Answer: d
Clarification: When starting a cut from the edge of a workpiece, cutting a form tool, slicing a tube or bar stock, or starting a cut from a large diameter start hole, is a slower process without submerged machining capabilities.

5. When parts with existing openings in them must be cut, conventional flushing produces _____
a) air pockets
b) unnecessary tapers
c) undercuts
d) poor flushing
Answer: a
Clarification: When parts with existing openings, slots or cross holes in them must be cut, conventional flushing produces air pockets and results in reduced performance or wire breaks. Submerged machining provides stable cutting of these parts.

6. When it is not possible to have the flushing nozzles close to the top or bottom of the workpiece _____ machines may require constant adjustment of the top and bottom flush.
a) submerged type
b) splash flush
c) rigid flush
d) stock flush
Answer: b
Clarification: When it is not possible to have the flushing nozzles close to the top or bottom of the workpiece, splash flush machines may require constant adjustment of the top and bottom flush. When machining submerged, you can adjust the flush once and forget it.

7. Which of the following is not the benefit of submerged cutting?
a) improved accuracy
b) better surface finish
c) Thermal stability
d) no wire breakage
Answer: d
Clarification: Benefits of submerged cutting are:
• Enhanced thermal stability of the entire set up
• Accurate skim cuts
• Better surface finish
• Improved accuracy.

8. Submerged cutting helps cutting the workpieces without hampering the flush.
a) True
b) False
Answer: a
Clarification: Cutting round stock or tubing presents a combination of adverse effects. Submerged cutting can efficiently cut these jobs without the flush being impaired.

9. Which of the following is not the effect of less maintenance of the wire cut EDM machines?
a) Wire breaks
b) Lines in the part
c) Lowered time to complete the job
d) Rough surfaces
Answer: c
Clarification: the lack of maintenance will lead to slower cutting speeds, size inaccuracy, lines in the part, wire breaks, a rougher surface finish, and (eventually) a service call. Maintenance of Wire EDM machine (or any EDM machine) usually consumes twenty to thirty minutes a week or less.

10. In how many of the following applications, wire cut EDM can be used?
– Manufacturing of progressive, blanking and trim dies
– Extrusion dies
– Cutting difficult to machine materials like hastaloy, inconel and titanium
– Cutting narrow slots and keyways
– Manufacturing of parts where burrs can’t be tolerated.
a) 1
b) 3
c) 4
d) 5
Answer: d
Clarification: Wire cut EDM has a broad range of applications that are continuing to grow. Some of them are listed below:
. Parts with complex geometry’s
. Parts requiring “tenths” tolerances
. Parts where burrs can’t be tolerated
. Thin or delicate parts that are susceptible to tool pressure
. Progressive, blanking and trim dies
. Extrusion dies
Precious metals
. Narrow slots and keyways
. Mold components
. Tooling for forging, or injection molding operations.
. Medical and dental instrumentation
. Cutting hardened materials such as carbide, C.B.N. and P.C.D.
Cutting difficult to machine materials like hastaloy, inconel and titanium
. Aerospace, defense and electronic parts
. Prototypes parts
Production parts
Form tools and inserts
Electrodes (graphite or copper) for vertical EDM.

Manufacturing Processes Multiple Choice Questions on “Annealing – 9”.

1. Grain cells having a number of sides _____ have grain walls which are concave inwards.
a) >3
b) <6
c) <8
d) >5
Answer: b
Clarification: The cells with less than 6 sides have walls that are primarily concave toward their centres. Those cells with more than 6 sides have walls convex toward their centres, this effect is more pronounced the larger the number of sides above 6.

2. Grain cells with _____ sides are unstable.
a) <3
b) >8
c) <6
d) >10
Answer: c
Clarification: All grain cells with less than 6 sides are basically unstable and tend to shrink in size and these grains will therefore shrink and eventually disappear during annealing; while grain cells with more than 6 sides tend to grow in size.

3. If the grain has 6 boundaries, the structure will be _____
a) stable
b) metastable
c) quasi-stable
d) non-planner
Answer: b
Clarification: If the grain has 6 boundaries, they will be planar and the structure metastable. However, if the total number of boundaries around grain is less than 6, each boundary must be concave inwards.

4. Grain boundary migration occurs to _____
a) increase the strain energy
b) increase the surface hardness
c) reduce grain boundary energy
d) reduce recrystallization temperature
Answer: c
Clarification: Large grains will have more than 6 boundaries and will grow. The overall result of boundary migration is to reduce the number of grains, thereby increasing the mean grain size and reducing the total grain boundary energy. This phenomenon is known as grain growth or grain coarsening.

5. The phenomenon of formation of grain boundary of much lower surface energy than that of the average boundary is known as _____
a) grain boundary coalescence
b) atomic coalescence
c) geometrical coalescence
d) grain boundary migration
Answer: c
Clarification: Geometrical coalescence can be simply described as an encounter of 2 grains whose relative orientations are such that the boundary formed between the 2 grains is one of much lower surface energy than that of the average boundary. In a polycrystalline metal, such a boundary would be equivalent to a sub-grain boundary.

6. The boundary atoms in the crystal on the _____ of the boundary are more tightly bound than the boundary atoms in the crystal in the _____
a) concave side, convex side
b) convex side, concave side
c) surface, inner side
d) surface, concave side
Answer: a
Clarification: The boundary atoms in the crystal on the concave side of the boundary are more tightly bound than the boundary atoms in the crystal in the convex side because they are more nearly surrounded by neighbouring atoms of the same crystal.

7. The rate at which atoms jumps from ______ is greater than that in the opposite direction.
a) convex side to concave side of the grain
b) surface high strain energy to surface of low strain energy
c) grain at higher temperature to grain at lower temperature
d) concave side to convex side of the grain
Answer: a
Clarification: Tighter binding of the atoms on the concave side of the boundary should make the rate at which atoms jump across the boundary from the convex to the concave crystal greater than that in the opposite direction. The greater the curvature of the boundary, then the greater should be this effect, and faster the movement of the crystal boundary.

8. If _________ then there will be an elastic stress field introduced into the lattice.
a) number of foreign atoms is more than that of parent crystal atoms
b) number of foreign atoms is less than that of parent crystal atoms
c) size of foreign atoms is different than that of the parent crystal atoms
d) temperature of foreign atoms is different than that of parent crystal atoms
Answer: c
Clarification: If the size of a foreign atom and that of the parent crystal are different, then there will be an elastic stress field introduced into the lattice by each foreign atom.

9. The strain energy of the grain boundary can be reduced by migration of the foreign atoms into the pure crystal grain.
a) True
b) False
Answer: a
Clarification: Since grain boundaries are regions of lattice misfit, the strain energy of the boundary, as well as that of the lattice surrounding a foreign atom, can be reduced by the migration of the foreign atom to the neighbourhood of the grain boundary.

10. Higher the temperature faster will be the grain growth.
a) True
b) False
Answer: a
Clarification: As the metal approaches 100% purity, the grain-growth exponent increases toward the theoretical value ½. Also, note that at the higher temperature (around 900 K) the rate of approach is faster.

Manufacturing Engineering Multiple Choice Questions on “Cutting Fluid and Tool Temperature”.

1. Primary deformation zone in metal cutting operation is located at:
a) Around shear plane
b) Tool chip interface
c) Tool work piece interface
d) Tool face
Answer: a
Clarification: Primary deformation is the zone where maximum deformation occurs and occurs around the shear plane.

2. Secondary deformation zone in metal cutting operation is located at:
a) Shear plane
b) Tool chip interface
c) Tool work piece interface
d) Tool face
Answer: b
Clarification: Secondary deformation zone has medium level of deformation and generally occurs in tool chip interface.

3. Temperature rise in primary deformation zone is generally due to:
a) Plastic deformation of metal in shear zone
b) Friction between tool and chip
c) Rubbing action of tool piece with work piece
d) None of the mentioned
Answer: a
Clarification: Due to plastic deformation of metal during chip formation, there is a gradual rise in temperature.

4. Temperature rise in secondary deformation zone is generally due to:
a) Plastic deformation of metal in shear zone
b) Friction between tool and chip
c) Rubbing action of tool piece with work piece
d) None of the mentioned
Answer: b
Clarification: Temperature rises due to relative motion between chip and tool against some friction. Friction is responsible for the heat generation.

5. If heat transferred to the atmosphere is neglected, then the average amount of heat in % carried away by chips is nearly equal to:
a) 70
b) 15
c) 20
d) 96
Answer: a
Clarification: About 70% of the heat is carried away by chips, if heat transferred to surrounding is neglected.

6. If heat transferred to atmosphere is neglected, then the average amount of heat in % transferred to tool is nearly equal to:
a) 70
b) 15
c) 20
d) 96
Answer: b
Clarification: About 15% of the total heat is transferred to tool, if heat transferred to the surrounding is neglected.

7. If heat transferred to atmosphere is neglected, then the average amount of heat in % transferred to work piece is nearly equal to:
a) 70
b) 15
c) 20
d) 96
Answer: b
Clarification: About 15% of the total heat is transferred to work piece if heat transferred to the surrounding is neglected.

8. By increasing cutting speed, amount of heat generated
a) Increases
b) Decreases
c) Remains constant
d) None of the mentioned
Answer: a
Clarification: With increase in cutting speed, friction increases and hence the amount of heat generated increases.

9. By increasing feed rate, amount of heat generated
a) Increases
b) Decreases
c) Remains constant
d) None of the mentioned
Answer: b
Clarification: With an increase in feed rate, friction time for generating heat decreases and hence the amount of heat generated increases.

10. Amount of heat generated in shear plane is:
a) Directly proportional to shear angle
b) Inversely proportional to shear angle
c) Does not depend on shear angle
d) None of the mentioned
Answer: b
Clarification: With an increase in shear angle amount of plastic deformation decreases and hence the amount of heat generated decreases.