ADDITIVE MANUFACTURING MAIN PAPER
ANSWERS AND QUESTIONS SET A+
✔✔what does layer thickness depend on ? - ✔✔how close the part produced is to the
computer model
✔✔other names for AM - ✔✔rapid prototyping; freeform fabrication ; direct digital
manufacturing
✔✔benefits of AM - ✔✔geometric shapes that could not be built any other way; no need
for process planning (all parts are built with same simple steps); rapid fabrication of
parts and complex components
✔✔fabrication of parts with customized properties - ✔✔(1) parts that are rigid in one
direction and compliant in another (2) parts with non-uniform density (3) multi-material
components (4) parts with non-homogenous material composition
✔✔Difference between AM and CNC
(Materials) - ✔✔CNC:
homogenous materials
mostly brittle metals and alloys
can work with softer materials
AM: many anisotropic materials
polymer
waxes
metals composites ceramics
✔✔Difference between AM and CNC (speed) - ✔✔CNC:
can remove materials quickly
needs lengthy setups and process planning
multi-stage process
finishing may take days or weeks
AM:
Likely to take hours
, can be single stage process
finishing may take hours or days
✔✔Difference between AM and CNC (complexity) - ✔✔CNC: bc spindle principle,
complex features may require the tool to travel to locations that are impossible
needs to break complex parts into components to be later assembled
AM: high capabilities as complexity increases; not hampered by undercuts and internal
features
✔✔Difference between AM and CNC(Accuracy) - ✔✔CNC: determined by the
positioning mechanisms for the three orthogonal axes
servo or stepper motors
AM: many machines operate within micrometer level resolution
different resolutions for each axis (vertical vs lateral)
vertical build axis determines the layer thickness and is of lower resolution
determine minimum feature size
✔✔Difference between AM and CNC (geometry and programming) - ✔✔CNC: surfaces
must be generated in 3d space
some geometries are difficult to reproduce with CNC tools
programming can be complex and takes into account machine and tool parameters
AM: machines break any part into a series of simple 2d cross sections with normal
thickness
little programming is needed
✔✔AM applications - ✔✔automotive lever arm; 10 hour build time for platform of 9
parts; custom sawing jig for a leveling osteotomy
✔✔Development of AM - ✔✔about 30 years old; required advances in supporting
technologies (processing power, graphics capability, machine control, networking,
integration )
✔✔Computer- Aided Design (CAD) - ✔✔solid modeling is preferred over surface
modeling; ensure that there is volume so fully enclosed surfaces;
✔✔What are surface models described by? (CAD) - ✔✔boundary curves- difficult to
connect together; gaps make it difficult to process by AM machines
✔✔STL CAD file format - ✔✔uses triangles to describe the surfaces to be built; each
triangle is described by 3 points and a vector that is normal to the facet that indicates
the outward side of the triangle;
✔✔STL drawbacks - ✔✔only describes shape and nothing else; complex shapes can
make the file large and cumbersome; it cannot take advantage of the multi-material
printing
ANSWERS AND QUESTIONS SET A+
✔✔what does layer thickness depend on ? - ✔✔how close the part produced is to the
computer model
✔✔other names for AM - ✔✔rapid prototyping; freeform fabrication ; direct digital
manufacturing
✔✔benefits of AM - ✔✔geometric shapes that could not be built any other way; no need
for process planning (all parts are built with same simple steps); rapid fabrication of
parts and complex components
✔✔fabrication of parts with customized properties - ✔✔(1) parts that are rigid in one
direction and compliant in another (2) parts with non-uniform density (3) multi-material
components (4) parts with non-homogenous material composition
✔✔Difference between AM and CNC
(Materials) - ✔✔CNC:
homogenous materials
mostly brittle metals and alloys
can work with softer materials
AM: many anisotropic materials
polymer
waxes
metals composites ceramics
✔✔Difference between AM and CNC (speed) - ✔✔CNC:
can remove materials quickly
needs lengthy setups and process planning
multi-stage process
finishing may take days or weeks
AM:
Likely to take hours
, can be single stage process
finishing may take hours or days
✔✔Difference between AM and CNC (complexity) - ✔✔CNC: bc spindle principle,
complex features may require the tool to travel to locations that are impossible
needs to break complex parts into components to be later assembled
AM: high capabilities as complexity increases; not hampered by undercuts and internal
features
✔✔Difference between AM and CNC(Accuracy) - ✔✔CNC: determined by the
positioning mechanisms for the three orthogonal axes
servo or stepper motors
AM: many machines operate within micrometer level resolution
different resolutions for each axis (vertical vs lateral)
vertical build axis determines the layer thickness and is of lower resolution
determine minimum feature size
✔✔Difference between AM and CNC (geometry and programming) - ✔✔CNC: surfaces
must be generated in 3d space
some geometries are difficult to reproduce with CNC tools
programming can be complex and takes into account machine and tool parameters
AM: machines break any part into a series of simple 2d cross sections with normal
thickness
little programming is needed
✔✔AM applications - ✔✔automotive lever arm; 10 hour build time for platform of 9
parts; custom sawing jig for a leveling osteotomy
✔✔Development of AM - ✔✔about 30 years old; required advances in supporting
technologies (processing power, graphics capability, machine control, networking,
integration )
✔✔Computer- Aided Design (CAD) - ✔✔solid modeling is preferred over surface
modeling; ensure that there is volume so fully enclosed surfaces;
✔✔What are surface models described by? (CAD) - ✔✔boundary curves- difficult to
connect together; gaps make it difficult to process by AM machines
✔✔STL CAD file format - ✔✔uses triangles to describe the surfaces to be built; each
triangle is described by 3 points and a vector that is normal to the facet that indicates
the outward side of the triangle;
✔✔STL drawbacks - ✔✔only describes shape and nothing else; complex shapes can
make the file large and cumbersome; it cannot take advantage of the multi-material
printing
