MECH502 Exam Questions with Detailed Verified
Answers 2026
Question 1
In powder bed fusion, the primary mechanism by which a laser transfers
energy to the powder particles is:
A. Convection
B. Radiation
C. Conduction and absorption
D. Advection
*Correct Answer: C. Conduction and absorption. *
Rationale: The laser beam transfers energy through radiation, but the actual
melting occurs through conduction and absorption of energy into the powder
bed. The key factor is absorption of laser energy, which depends on the
material's absorptivity and the wavelength of the laser.
Question 2
The laser scanning strategy in selective laser melting directly influences the
part's:
A. Color and texture
B. Microstructure and residual stress distribution
C. Electrical conductivity only
D. Chemical composition
*Correct Answer: B. Microstructure and residual stress distribution. *
Rationale: The scan strategy (including hatch spacing, scan angle rotation,
and island scanning) affects thermal gradients, cooling rates, and the
,resulting grain structure, which influence mechanical properties and residual
stress buildup. Variations in scan vector length and direction can mitigate
warping and improve part quality.
Question 3
What is the "melt pool" in the context of powder bed fusion?
A. The un-melted powder surrounding the laser path
B. The region of material that is molten during laser exposure
C. The solidified track left after the laser passes
D. The heat-affected zone around the laser path
*Correct Answer: B. The region of material that is molten during laser
exposure. *
Rationale: The melt pool is the volume of material that is temporarily in a
liquid state as the laser traverses the powder bed. Its size and stability
significantly affect the final part quality, porosity, and mechanical properties.
Question 4
In directed energy deposition, the feedstock material is commonly
delivered as:
A. Liquid photopolymer
B. Powder or wire
C. Sheet material
D. Granular plastic pellets
*Correct Answer: B. Powder or wire. *
Rationale: DED systems use either metal powder (blown powder) or wire
(wire-fed DED) as the feedstock. Wire-fed DED has higher deposition rates
,and lower material waste, while powder-fed DED offers better resolution and
material flexibility.
Question 5
A key process parameter in binder jetting that affects the final density of
the part after sintering is:
A. Layer height only
B. Binder saturation level and sintering temperature
C. Print bed temperature
D. UV exposure time
*Correct Answer: B. Binder saturation level and sintering
temperature. *
Rationale: Binder saturation determines how much binder is deposited
relative to the powder, affecting green part strength. The sintering
temperature and time during post-processing control how much the powder
particles fuse, ultimately determining the final part density and mechanical
properties.
Question 6
The "hatch distance" in powder bed fusion refers to:
A. The distance between the laser and the powder bed
B. The distance between adjacent laser scan lines
C. The distance between layers
D. The distance between support structures
*Correct Answer: B. The distance between adjacent laser scan lines. *
, Rationale: Hatch distance (or hatch spacing) is the distance between parallel
scan lines within a layer. A smaller hatch distance increases overlap between
tracks, improving density but increasing build time. It is a critical parameter
for controlling porosity and surface finish.
Question 7
Thermal warping in powder bed fusion is primarily caused by:
A. Inadequate laser power
B. Non-uniform thermal contraction during cooling
C. Excessive powder layer thickness
D. Incorrect gas flow rate
*Correct Answer: B. Non-uniform thermal contraction during cooling. *
Rationale: The rapid and non-uniform heating and cooling during PBF create
thermal gradients that lead to differential contraction, resulting in residual
stresses and warping. Preheating the build plate and using a heated chamber
can help mitigate this issue.
Question 8
In the context of additive manufacturing, "isotropic" properties means:
A. Properties vary with build direction
B. Properties are the same in all directions
C. Properties vary with temperature
D. Properties vary with humidity
*Correct Answer: B. Properties are the same in all directions. *
Answers 2026
Question 1
In powder bed fusion, the primary mechanism by which a laser transfers
energy to the powder particles is:
A. Convection
B. Radiation
C. Conduction and absorption
D. Advection
*Correct Answer: C. Conduction and absorption. *
Rationale: The laser beam transfers energy through radiation, but the actual
melting occurs through conduction and absorption of energy into the powder
bed. The key factor is absorption of laser energy, which depends on the
material's absorptivity and the wavelength of the laser.
Question 2
The laser scanning strategy in selective laser melting directly influences the
part's:
A. Color and texture
B. Microstructure and residual stress distribution
C. Electrical conductivity only
D. Chemical composition
*Correct Answer: B. Microstructure and residual stress distribution. *
Rationale: The scan strategy (including hatch spacing, scan angle rotation,
and island scanning) affects thermal gradients, cooling rates, and the
,resulting grain structure, which influence mechanical properties and residual
stress buildup. Variations in scan vector length and direction can mitigate
warping and improve part quality.
Question 3
What is the "melt pool" in the context of powder bed fusion?
A. The un-melted powder surrounding the laser path
B. The region of material that is molten during laser exposure
C. The solidified track left after the laser passes
D. The heat-affected zone around the laser path
*Correct Answer: B. The region of material that is molten during laser
exposure. *
Rationale: The melt pool is the volume of material that is temporarily in a
liquid state as the laser traverses the powder bed. Its size and stability
significantly affect the final part quality, porosity, and mechanical properties.
Question 4
In directed energy deposition, the feedstock material is commonly
delivered as:
A. Liquid photopolymer
B. Powder or wire
C. Sheet material
D. Granular plastic pellets
*Correct Answer: B. Powder or wire. *
Rationale: DED systems use either metal powder (blown powder) or wire
(wire-fed DED) as the feedstock. Wire-fed DED has higher deposition rates
,and lower material waste, while powder-fed DED offers better resolution and
material flexibility.
Question 5
A key process parameter in binder jetting that affects the final density of
the part after sintering is:
A. Layer height only
B. Binder saturation level and sintering temperature
C. Print bed temperature
D. UV exposure time
*Correct Answer: B. Binder saturation level and sintering
temperature. *
Rationale: Binder saturation determines how much binder is deposited
relative to the powder, affecting green part strength. The sintering
temperature and time during post-processing control how much the powder
particles fuse, ultimately determining the final part density and mechanical
properties.
Question 6
The "hatch distance" in powder bed fusion refers to:
A. The distance between the laser and the powder bed
B. The distance between adjacent laser scan lines
C. The distance between layers
D. The distance between support structures
*Correct Answer: B. The distance between adjacent laser scan lines. *
, Rationale: Hatch distance (or hatch spacing) is the distance between parallel
scan lines within a layer. A smaller hatch distance increases overlap between
tracks, improving density but increasing build time. It is a critical parameter
for controlling porosity and surface finish.
Question 7
Thermal warping in powder bed fusion is primarily caused by:
A. Inadequate laser power
B. Non-uniform thermal contraction during cooling
C. Excessive powder layer thickness
D. Incorrect gas flow rate
*Correct Answer: B. Non-uniform thermal contraction during cooling. *
Rationale: The rapid and non-uniform heating and cooling during PBF create
thermal gradients that lead to differential contraction, resulting in residual
stresses and warping. Preheating the build plate and using a heated chamber
can help mitigate this issue.
Question 8
In the context of additive manufacturing, "isotropic" properties means:
A. Properties vary with build direction
B. Properties are the same in all directions
C. Properties vary with temperature
D. Properties vary with humidity
*Correct Answer: B. Properties are the same in all directions. *
