Re: AppleMac -> STL?

From: William D. Richards (
Date: Mon May 29 2000 - 23:59:06 EEST


I can echo what the others have said. I use form-Z as my main
modeling program, and it has always saved perfect STL files for use
with rapid prototyping.

The only times I have had problems saving to STL was when I would be
trying to save a model that had imperfections in it (i.e.: Designer
error). In this event, form-Z would open a dialogue window stating
what the problems were with the file.

The trick is to recognize when there is a possibility of errors
creeping into the model, and take appropriate action during that
phase of the design. Usually, this will be when trying to merge
object-A onto a region of object-B where that has small, numerous,
and complex geometries. The result may generate intersecting
triangles in the STL file.

Another situation that can create problems is when working with
surface objects, as opposed to solid objects. If the surface is open
at any point, it means that the object you generated has no "inside."
You cannot generate an STL file from an open surface. If you create a
flat square, both sides of the square are outside. STL needs to be
able to differentiate between "inside" and "outside." You would be
stunned at the number of times I come across new 3D designers who
have difficulty with this concept! So often I get the comment, "Well
-- it rendered a good image of the object!"

Make sure while working with surface objects that ALL surfaces are
stitched together! Just overlapping surfaces might make them look
like one object, but they aren't. There is a big difference between
"looking good" and "being good!"

In the end, I have found that most of the software used to prepare
the STL file into the machine code for the given RP machine is pretty
robust in accepting and dealing with errors in the STL file. So a few
bad triangles can be accepted.

Bill Richards
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