http://www.design-engineering.com May/June | 2019CADReport 17
- Generate prototypes more quickly,
to avoid overnighting to outside
manufacturers - Minimize material cost and weight,
to the benefit of surgical and
aviation applications
Sure, mistakes are made with subtrac-
tive manufacturing, but mistakes seem
more precarious in additive manufactur-
ing. While SM works from g-code, AM
works with STL files exported from CAD.
STL is a simplistic format that consists
purely of 3D coordinates for the myriad
of triangles defining the surfaces of mod-
els; the format doesn’t even include units.
It’s these surfaces and the triangles that
then create problems for 3D printers:- Too thin walls that lead to collapsed
3 D prints. - Non-watertight designs due to one
or more holes in surfaces and/or
edges that don’t match - Too many triangles used to define
surfaces or ones that overlap
unnecessarily - Triangles with inverted normals or
ones that cut into each other.
Software firm Materialize reports
that one in five parts fail during 3D
printing, because walls were too thin.
As a result, an entire sub-industry has
sprung up to write software that fixes
these problems and optimizes the 3D
printing process, such as by “shrink
wrapping” the CAD model to make a
shell copy of the 3D solid. All this capa-
bility ought to be in MCAD.
We see market inefficiencies in the
disconnect between CAD and CAM that
has gone on for 50 years. The linkage
between CAD and final product is pretty
tight for some MCAD, but completely
lacking in other major disciplines, such
as architectural and civil engineering.
Small firms are successful in filling in
the niches ignored by big CAD, espe-
cially in the areas of kitchen cabinets
and 3D printing. DERalph Grabowski writes on the business
of CAD on his WorldCAD Access blog
(www.worldcadaccess.com) and weekly
upFront.eZine newsletter. He has
authored many articles and books on
AutoCAD, BricsCAD, Visio and other
design software.RotoPrecision JanFeb2018.indd 1 2018-01-12 8:03 AMDES_MAYJUNE19_LAZ.indd 17 2019-05-23 12:55 PM