MECH502 Exam Questions with Detailed
Verified Answers 2026-2027
Question 1
In powder bed fusion, a "Melt Flow Index" is used to help determine:
A. The optimal laser power
B. If powder is reusable
C. The layer thickness
D. The scanning speed
*Correct Answer: B. If powder is reusable. *
Rationale: The melt flow index measures how well powder flows, which
indicates whether it can be reused for subsequent prints. Degraded powder
has altered flow characteristics and may not produce good parts.
Question 2
True or False: Hot iso-static pressing (HIP) is a method for densifying metal
parts created with powder-based fusion processes.
A. True
B. False
*Correct Answer: A. True. *
Rationale: HIP applies high temperature and pressure to eliminate porosity in
metal parts, improving mechanical properties and density. It is commonly
used as a post-processing step for powder bed fusion parts.
,Question 3
The slope of a photopolymer's working curve represents:
A. The curing speed of the resin
B. The distance a given irradiance will decrease by an amount equal to
the half-width of the gaussian, as it penetrates a given photopolymer
C. The viscosity of the resin
D. The depth of cure per layer
*Correct Answer: B. The distance a given irradiance will decrease by an
amount equal to the half-width of the gaussian, as it penetrates a
given photopolymer. *
Rationale: The working curve slope (Dp) describes how light intensity
attenuates as it penetrates the photopolymer. This is a critical parameter for
determining exposure settings in vat photopolymerization.
Question 4
Your boss emails you a picture of an object that is 10 μm long and 7 μm
high, made of urethane acrylate. What is most likely the AM process used
to make this part?
A. Stereolithography (SLA)
B. Digital Light Processing (DLP)
C. Two-photon photopolymerization
D. Inkjet printing
*Correct Answer: C. Two-photon photopolymerization. *
Rationale: Two-photon photopolymerization (TPP) is capable of fabricating
features at the micro- and nanoscale (down to tens of nanometers). The small
size (10 μm) and material (urethane acrylate) are characteristic of TPP.
,Question 5
Your colleague asks you which AM process was most likely used to make a
titanium object that is fully dense and has a rough, grainy surface. What do
you tell him?
A. Binder Jetting
B. Powder Bed Fusion
C. Directed Energy Deposition
D. Material Extrusion
*Correct Answer: B. Powder Bed Fusion. *
Rationale: Powder bed fusion (SLM/DMLS) can produce fully dense metal
parts from titanium powder. The rough, grainy surface is characteristic of the
as-printed surface finish from powder bed fusion.
Question 6
Which AM process is most likely used to produce a part that is made of a
ceramic slurry?
A. Stereolithography
B. Binder Jetting
C. Direct-write
D. Sheet Lamination
*Correct Answer: C. Direct-write. *
Rationale: Direct-write (or direct ink writing) is an extrusion-based AM
process that can deposit ceramic slurries (pastes) to create 3D structures. This
is commonly used for fabricating ceramic scaffolds and components.
, Question 7
Lack of fusion (LOF) in powder bed fusion is primarily caused by:
A. Excessive laser power
B. Insufficient energy density, high scan speed, or large hatch spacing
C. Oxidation of the powder
D. Inadequate gas flow
*Correct Answer: B. Insufficient energy density, high scan speed, or
large hatch spacing. *
Rationale: Lack of fusion occurs when the energy input is insufficient to
properly melt and overlap the powder particles and previous layers, resulting
in sharp-edged voids that act as stress concentrators.
Question 8
Which of the following is a common defect in additive manufacturing
characterized by the formation of spherical droplets instead of a continuous
track?
A. Delamination
B. Porosity
C. Balling
D. Cracking
*Correct Answer: C. Balling. *
Rationale: Balling is a defect where molten material forms spherical droplets
instead of a continuous track due to surface tension effects. This is often
caused by improper process parameters or material properties.
Verified Answers 2026-2027
Question 1
In powder bed fusion, a "Melt Flow Index" is used to help determine:
A. The optimal laser power
B. If powder is reusable
C. The layer thickness
D. The scanning speed
*Correct Answer: B. If powder is reusable. *
Rationale: The melt flow index measures how well powder flows, which
indicates whether it can be reused for subsequent prints. Degraded powder
has altered flow characteristics and may not produce good parts.
Question 2
True or False: Hot iso-static pressing (HIP) is a method for densifying metal
parts created with powder-based fusion processes.
A. True
B. False
*Correct Answer: A. True. *
Rationale: HIP applies high temperature and pressure to eliminate porosity in
metal parts, improving mechanical properties and density. It is commonly
used as a post-processing step for powder bed fusion parts.
,Question 3
The slope of a photopolymer's working curve represents:
A. The curing speed of the resin
B. The distance a given irradiance will decrease by an amount equal to
the half-width of the gaussian, as it penetrates a given photopolymer
C. The viscosity of the resin
D. The depth of cure per layer
*Correct Answer: B. The distance a given irradiance will decrease by an
amount equal to the half-width of the gaussian, as it penetrates a
given photopolymer. *
Rationale: The working curve slope (Dp) describes how light intensity
attenuates as it penetrates the photopolymer. This is a critical parameter for
determining exposure settings in vat photopolymerization.
Question 4
Your boss emails you a picture of an object that is 10 μm long and 7 μm
high, made of urethane acrylate. What is most likely the AM process used
to make this part?
A. Stereolithography (SLA)
B. Digital Light Processing (DLP)
C. Two-photon photopolymerization
D. Inkjet printing
*Correct Answer: C. Two-photon photopolymerization. *
Rationale: Two-photon photopolymerization (TPP) is capable of fabricating
features at the micro- and nanoscale (down to tens of nanometers). The small
size (10 μm) and material (urethane acrylate) are characteristic of TPP.
,Question 5
Your colleague asks you which AM process was most likely used to make a
titanium object that is fully dense and has a rough, grainy surface. What do
you tell him?
A. Binder Jetting
B. Powder Bed Fusion
C. Directed Energy Deposition
D. Material Extrusion
*Correct Answer: B. Powder Bed Fusion. *
Rationale: Powder bed fusion (SLM/DMLS) can produce fully dense metal
parts from titanium powder. The rough, grainy surface is characteristic of the
as-printed surface finish from powder bed fusion.
Question 6
Which AM process is most likely used to produce a part that is made of a
ceramic slurry?
A. Stereolithography
B. Binder Jetting
C. Direct-write
D. Sheet Lamination
*Correct Answer: C. Direct-write. *
Rationale: Direct-write (or direct ink writing) is an extrusion-based AM
process that can deposit ceramic slurries (pastes) to create 3D structures. This
is commonly used for fabricating ceramic scaffolds and components.
, Question 7
Lack of fusion (LOF) in powder bed fusion is primarily caused by:
A. Excessive laser power
B. Insufficient energy density, high scan speed, or large hatch spacing
C. Oxidation of the powder
D. Inadequate gas flow
*Correct Answer: B. Insufficient energy density, high scan speed, or
large hatch spacing. *
Rationale: Lack of fusion occurs when the energy input is insufficient to
properly melt and overlap the powder particles and previous layers, resulting
in sharp-edged voids that act as stress concentrators.
Question 8
Which of the following is a common defect in additive manufacturing
characterized by the formation of spherical droplets instead of a continuous
track?
A. Delamination
B. Porosity
C. Balling
D. Cracking
*Correct Answer: C. Balling. *
Rationale: Balling is a defect where molten material forms spherical droplets
instead of a continuous track due to surface tension effects. This is often
caused by improper process parameters or material properties.
