Additive Manufacturing – Exam UPDATED
Questions And CORRECT Answers
Describe the process of creating a 3D-printed object - CORRECT ANSWER - -Creation of
CAD
-Meshing/conversion to STL file
-Slicing
-Planning
-Printing
-Post-processing
Describe the "Meshing" step of the 3D-printing process. - CORRECT ANSWER - (, or
conversion to an STL file) - the CAD package must be able to export the object in a manner that
the subsequent steps can handle. The "mathematical" CAD model is discretized into a collection
of triangles that represent the outer surface of the desired object. At this point, comprimises in
terms of accuracy (resolution) and file size are made.
Describe the "Slicing" step of the 3D-printing process. - CORRECT ANSWER - Most
(all?) printers can handle a single 2-dimensions
at a time. The slicing process breaks the model into, usually
horizontal, slices so that each one can be handled independently.
This height should be matched to the physical height
of each layer the printer creates.
Describe the "Planning" step of the 3D-printing process. - CORRECT ANSWER - The
tool path (route) required to generate each
slice must be planned. (This does not occur in image-based
photopolymerization methods.)
Describe the "Post-processing" step of the 3D-printing process. - CORRECT ANSWER -
Many printing methods require some sort of post-processing such as removal of support material
, or completion of curing. (Since one could argue that this is not part of the printing process, I will
not deduct points if you have not listed it.)
What is hysteresis? - CORRECT ANSWER - Hysteresis describes a relationship between
two or more parameters that is not simply defined, but in which the history of the independent
parameter(s) is important.
Give two examples of hysteresis - CORRECT ANSWER - - Positional control of
mechanical components in the printers.
- Phase changes often occur at different temperatures.
- Advancing and Receding contact angles often differ
- Non-newtonian fluids often exhibit hysteresis.
- Plastic deformation of material during physical stress testing exhibits something like hysteresis.
Give an example of when positional control of mechanical components in the printers is an
example of hysteresis - CORRECT ANSWER - Positional control of mechanical
components in the printers (motors, belts, gears, screws all have "gaps", causing a discrepency
between where the motor tries to position a component and where it actually ends up. This
usually depends on the direction of approach.
Explain why phase changes that often occur at different temperatures is an example of hysteresis
- CORRECT ANSWER - Theoretically pure materials shouldn't phase transit at different
temperatures, therefor are the fact that they don't a example of hysteresis.
Explain how "advancing and receding contact angles often differ" is an example of hysteresis -
CORRECT ANSWER - The contact angle depends on whether the drop is growing or
shrinking
Give an example of when non-newtonian fluids exhibits hysteresis. - CORRECT
ANSWER - Shear-thinning or shear-thickening materials often require a bit
of time to "rearrange" after a change in shear rate, making it
possible to measure two different shear stresses for the same
Questions And CORRECT Answers
Describe the process of creating a 3D-printed object - CORRECT ANSWER - -Creation of
CAD
-Meshing/conversion to STL file
-Slicing
-Planning
-Printing
-Post-processing
Describe the "Meshing" step of the 3D-printing process. - CORRECT ANSWER - (, or
conversion to an STL file) - the CAD package must be able to export the object in a manner that
the subsequent steps can handle. The "mathematical" CAD model is discretized into a collection
of triangles that represent the outer surface of the desired object. At this point, comprimises in
terms of accuracy (resolution) and file size are made.
Describe the "Slicing" step of the 3D-printing process. - CORRECT ANSWER - Most
(all?) printers can handle a single 2-dimensions
at a time. The slicing process breaks the model into, usually
horizontal, slices so that each one can be handled independently.
This height should be matched to the physical height
of each layer the printer creates.
Describe the "Planning" step of the 3D-printing process. - CORRECT ANSWER - The
tool path (route) required to generate each
slice must be planned. (This does not occur in image-based
photopolymerization methods.)
Describe the "Post-processing" step of the 3D-printing process. - CORRECT ANSWER -
Many printing methods require some sort of post-processing such as removal of support material
, or completion of curing. (Since one could argue that this is not part of the printing process, I will
not deduct points if you have not listed it.)
What is hysteresis? - CORRECT ANSWER - Hysteresis describes a relationship between
two or more parameters that is not simply defined, but in which the history of the independent
parameter(s) is important.
Give two examples of hysteresis - CORRECT ANSWER - - Positional control of
mechanical components in the printers.
- Phase changes often occur at different temperatures.
- Advancing and Receding contact angles often differ
- Non-newtonian fluids often exhibit hysteresis.
- Plastic deformation of material during physical stress testing exhibits something like hysteresis.
Give an example of when positional control of mechanical components in the printers is an
example of hysteresis - CORRECT ANSWER - Positional control of mechanical
components in the printers (motors, belts, gears, screws all have "gaps", causing a discrepency
between where the motor tries to position a component and where it actually ends up. This
usually depends on the direction of approach.
Explain why phase changes that often occur at different temperatures is an example of hysteresis
- CORRECT ANSWER - Theoretically pure materials shouldn't phase transit at different
temperatures, therefor are the fact that they don't a example of hysteresis.
Explain how "advancing and receding contact angles often differ" is an example of hysteresis -
CORRECT ANSWER - The contact angle depends on whether the drop is growing or
shrinking
Give an example of when non-newtonian fluids exhibits hysteresis. - CORRECT
ANSWER - Shear-thinning or shear-thickening materials often require a bit
of time to "rearrange" after a change in shear rate, making it
possible to measure two different shear stresses for the same
