2. Development of a CAD model
•Conversion of an existing two dimensional
(2D) drawing
•Importing scanned point data into a CAD
package
•Creating a new part in CAD in various solid
modeling packages
•Altering an existing CAD model
5. Support Structures
As the parts are going to be built in layers, and
there may be areas that could float away or of
overhang which could distort.
Therefore, some processes require a base and
support structures to be added to the file which
are built as part of the model and later
removed.
6. Manufacturing
•RP process is additive i.e. it builds the parts up in
layers of material from the bottom.
•Each layer is automatically bonded to the layer
below and the process is repeated until the part is
built.
•This process of bonding is undertaken in different
ways for the various materials that are being used
but includes the use of Ultraviolet (UV) lasers,
Carbon Dioxide lasers, heat sensitive glues and
melting the material itself etc.
7. Post processing
•Removal of part from platform
• Removal of supports from part
• Cleaning of part (wiping, rinsing, ... )
• Finishing part (curing, sanding, polishing, … )
8. Some issues in RP
Effect of layer thickness on stair stepping effect
Effect of layer thickness on stair stepping effect
9. STL FILE PROBLEMS
(1) Gaps (cracks, holes, punctures) that is, missing
facets.
(2) Degenerate facets (where all its edges are
collinear).
(3) Overlapping facets.
(4) Non-manifold topology conditions.
10. Missing Facets or Gaps
Tessellation of surfaces with large curvature can result in errors at the
intersections between such surfaces, leaving gaps or holes along edges
of the part model
11. Degenerate Facets
A geometrical degeneracy of a facet occurs when all of the facets’
edges are collinear even though all its vertices are distinct.
