Re: Stupid STL Question

From: William D. Richards (
Date: Sat Mar 16 2002 - 17:46:40 EET

One thing I've found over the years, is that people refuse to believe or
understand that STL is a one way street. STL was created with the
purpose of driving a rapid prototyping machine (the SLA). The STL object
created from a model is only an approximation of the CAD model, not a
true representation. What it boils down to, you can't edit an STL file.
It was never meant to be an "editable" format. If you need to make
changes to the object, you should turn to the original model in the
original CAD system it was designed in. Your life will be much, MUCH

An STL file contains a model that defines a volume with a faceted
surface. It is in no way a smooth surface. In addition, it is an
approximation of the original model, not a perfect copy. So to actually
convert an STL into a parasolid would be extremely difficult. This, and
the fact that STL was never a format meant to be reversed, is why you
are having such a difficult time trying to "convert" the STL file. There
is no way to get an accurate model from an STL.

Now, all that being said, anyone who has tried to run more than three
models on any RP system will recognize the fact that STL files are not
quite perfect. There will come a time when one needs to edit that STL
file. In this case, the best choice is usually Magics by Materialize.

If the model is so important that you need to modify it to add features,
smooth surfaces, etc., and the original file was erased, lost, or is not
yours, then the best move would be to sit down at a computer with a
competent 3D CAD package and start creating a new model. Believe me,
that IS the quickest way! (even if it is very aggravating to actually
have to do it.)

        - Bill Richards

                " There is no such thing as a stupid question. If you don't
ask, you'll never know."
                                                        Tom Carhart, 1982

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