ADDITIVE MANUFACTURING UPDATED EXAMS
ANSWERS AND QUESTIONS SET A+
✔✔infinitesimal thickness - ✔✔surface can be exported to STL "as is" but most printers
would have a problem because it is too thin
✔✔conversion to STL - ✔✔minimum triangle size is set in the CAD system; idea is to
make them small enough that no triangle is shown on the surface; this is a function of
the distance between the plane of the triangle and the surface it is supposed to
represent;
✔✔what is matlab's approach to conversion to stl - ✔✔divide every square facet into
two triangular elements (create shells, add thickness and cleanup file)
✔✔Color and Graphics - ✔✔can be assigned to a material , region, or vertex; specified:
fixed RGBA values, by formula, by reference to an image
✔✔File transfer to AM machine and STL file manipulation - ✔✔once file is created, it
can be sent to the AM machine; sometimes ready for "print button" most often times, it
requires some manipulation
✔✔machine setup - ✔✔setup of parameters that are specific to the machine or process;
some machines are very simple and have few parameters while others have many;
some parameters may require optimization of settings
tradeoff: time versus resolution (layer thickness)
✔✔what happens if the machine is setup incorrectly? - ✔✔machine will still build part
but quality may be unacceptable (freaky dragon picture)
✔✔build - ✔✔mostly computer controlled; layer by layer building phase; layer control
plus layer cross section formation;
, ✔✔removal and cleanup - ✔✔separation from platform or removal from vat; some
degree of manual skill is needed; support is needed in various locations
some machines print sacrificial material (layers) to facilitate removal
✔✔post processing - ✔✔highly manual process (due to complexity of parts)
may involve polishing, painting or application of coatings
require careful ahndling to maintain good precision and finish
✔✔what kind of post processing is required for relatively fragile components? - ✔✔they
may need some infiltration process or surface coating to strengthen the part; some
powder parts may involve the use of furnaces to turn "green parts" into finished
products
✔✔Part Orientation - ✔✔orientation may affect part accuracy
for non symmetrical complex parts, there may not be an ideal orientation
✔✔time to build (Part Orientation ) - ✔✔taller builds take longer than shorter ones, so
high aspect ratio parts might be better built lying down
✔✔support structures (part orientation ) - ✔✔some orientations naturally require more
support generation and the orientation will also determine the location are touched by
the support structures
✔✔surface finish (part orientation) - ✔✔any down facing surface will be or poorer quality
than surfaces pointing upwards
✔✔Removal of Supports - ✔✔supports amplify the problem of surface finish; whenever
the support structures meet the part, there will be marks remaining after removal so you
need to reduce the number of supports (reduce cleanup and post processing ); drain
holes might be needed for pools of trapped liquid
✔✔hollowing out parts - ✔✔might be desirable to hollow out features that do not affect
functionality; greatly reduces build time and material consumption; both impact final cost
however, designing custom honeycomb or truss-like structures might take additional
design time
✔✔Interlocking Features - ✔✔AM often have a limitation on the volume they can build;
large parts would then have to be broken down into smaller pieces for independent
fabrication and subsequent assembly ; features can be designed to have large area for
adhesive bonding
✔✔Reduction of Part count in an assembly - ✔✔great opportunities to reduce the widely
accepted DFMA principle of "reducing part count" arise with the use of AM
ANSWERS AND QUESTIONS SET A+
✔✔infinitesimal thickness - ✔✔surface can be exported to STL "as is" but most printers
would have a problem because it is too thin
✔✔conversion to STL - ✔✔minimum triangle size is set in the CAD system; idea is to
make them small enough that no triangle is shown on the surface; this is a function of
the distance between the plane of the triangle and the surface it is supposed to
represent;
✔✔what is matlab's approach to conversion to stl - ✔✔divide every square facet into
two triangular elements (create shells, add thickness and cleanup file)
✔✔Color and Graphics - ✔✔can be assigned to a material , region, or vertex; specified:
fixed RGBA values, by formula, by reference to an image
✔✔File transfer to AM machine and STL file manipulation - ✔✔once file is created, it
can be sent to the AM machine; sometimes ready for "print button" most often times, it
requires some manipulation
✔✔machine setup - ✔✔setup of parameters that are specific to the machine or process;
some machines are very simple and have few parameters while others have many;
some parameters may require optimization of settings
tradeoff: time versus resolution (layer thickness)
✔✔what happens if the machine is setup incorrectly? - ✔✔machine will still build part
but quality may be unacceptable (freaky dragon picture)
✔✔build - ✔✔mostly computer controlled; layer by layer building phase; layer control
plus layer cross section formation;
, ✔✔removal and cleanup - ✔✔separation from platform or removal from vat; some
degree of manual skill is needed; support is needed in various locations
some machines print sacrificial material (layers) to facilitate removal
✔✔post processing - ✔✔highly manual process (due to complexity of parts)
may involve polishing, painting or application of coatings
require careful ahndling to maintain good precision and finish
✔✔what kind of post processing is required for relatively fragile components? - ✔✔they
may need some infiltration process or surface coating to strengthen the part; some
powder parts may involve the use of furnaces to turn "green parts" into finished
products
✔✔Part Orientation - ✔✔orientation may affect part accuracy
for non symmetrical complex parts, there may not be an ideal orientation
✔✔time to build (Part Orientation ) - ✔✔taller builds take longer than shorter ones, so
high aspect ratio parts might be better built lying down
✔✔support structures (part orientation ) - ✔✔some orientations naturally require more
support generation and the orientation will also determine the location are touched by
the support structures
✔✔surface finish (part orientation) - ✔✔any down facing surface will be or poorer quality
than surfaces pointing upwards
✔✔Removal of Supports - ✔✔supports amplify the problem of surface finish; whenever
the support structures meet the part, there will be marks remaining after removal so you
need to reduce the number of supports (reduce cleanup and post processing ); drain
holes might be needed for pools of trapped liquid
✔✔hollowing out parts - ✔✔might be desirable to hollow out features that do not affect
functionality; greatly reduces build time and material consumption; both impact final cost
however, designing custom honeycomb or truss-like structures might take additional
design time
✔✔Interlocking Features - ✔✔AM often have a limitation on the volume they can build;
large parts would then have to be broken down into smaller pieces for independent
fabrication and subsequent assembly ; features can be designed to have large area for
adhesive bonding
✔✔Reduction of Part count in an assembly - ✔✔great opportunities to reduce the widely
accepted DFMA principle of "reducing part count" arise with the use of AM
