Re: STL files - "totally unusable" ?

From: Bharath Vasudeva Rao (
Date: Fri Apr 14 2000 - 23:51:26 EEST

I was working with two files on Autocad trying to get a good STL file. But
that never worked out. I was just trying out various options.
Then I did an export to 3DSMAX file and read that in Rhino and did an export
to STL and I got a good STL file.


Research Assistant
Partnership for Research in Stereo Modeling (PRISM), ASU
PRISM (480) 9657830 / Office (480) 9650574 / Home (480) 4469259

On Fri, 14 Apr 2000, Vesna Cota wrote:

> Hello Jorn and all the others,
> I have been reading and listening about this "totally unusable STL files
> from AutoCAD and Mechanical Desktop" for years and can't stop wondering
> what's going on. I have been creating STL files from AutoCAD since its first
> solid modeling extension AME became available. In all those years I seldom
> had any problems.
> I am using Mechanical Desktop now along with ProE, and you couldn't tell
> which one I used to create the STL file. With AutoCAD it is very important
> to set your facetres variable to a high value (default is 0.5, highest is
> 10, I never go below 8). With Mechanical Desktop I still use the AutoCAD
> STLOUT command ( which means I explode my parts to make them genuine AutoCAD
> solids ), mainly because the MDT amstlout command creates ASCII files and I
> prefer smaller and cleaner binary output.
> Obviously, once a bad stl file is created it takes much more effort to fix
> it ( if possible at all) and it is difficult to know how it compares to the
> original part if you don't have both. Before attempting to fix the STL file,
> try to create a better STL output.
> I never had any problems with metric parts, but it did happen with imperial
> units. Because of the settings in AutoCAD, when working in inches the max
> facetres setting of 10 may be too small and triangles may end up too big to
> represent small radii, making them either disappear or turn into chamfers.
> In those cases I would scale up the model (25.4 times as an example, but it
> could be 100 or anything else as needed), create the STL output and let the
> RP supplier know that the model is scaled up. He would scale the STL output
> of the part down and keep the definition at the same time. It's not as
> straight forward as typing stlout, but it works every time.
> Another option may be to export the SAT file ( acisout in AutoCAD, amacisout
> in Mechanical Desktop). Acis file can be imported in many other CAD packages
> and the STL file can be exported from there. I never had to use this
> approach. The acis file can be checked out using the ACIS viewer from
> Spatial Technologies. Great tool, by the way!
> If the Acis output doesn't work, I would suspect the part has a flaw.
> Ultimately, it boils down to the poor design approach. And that will
> generally have more to do with the training of the user than with the
> software itself. ... which is a whole new story.
> AutoCAD users may need more information regarding generation of good stl
> files and some help if it doesn't work out. Hopefully this will provide a
> bit of it.
> I just started testing the Autodesk Inventor. I'll let you know how it
> works.
> Regards,
> Vesna
> Vesna Cota
> Industry Consultant
> RPMV Technologies
> 10464 Hwy 48
> Markham, Ontario
> L3P 3J3 Canada
> -----Original Message-----
> From: []
> Sent: Friday, April 14, 2000 10:32 AM
> To:;
> Cc:
> Subject: Re: - a new web service for RP
> Jorn and list ;
> You are absolutly right. We have recieved many files from Mechanical Desktop
> and also the new Inventor from Autodesk. We have the same problem, the STL
> files are totally unusable for RP. I have yet to recieve a valid STL file
> from an Autodesk product (since 1983). I have the same problems with SDRC so
> I guess Autodesk is not alone. It's no wonder why all the STL fix programs
> are doing such a brisk business when the major Cad vendors put out such
> junk.
> Its funny we very seldom have any difficulties with ProE, Solidworks, Catia,
> or even UG (used to be McAuto). So if it can be done why can't they all do
> it
> right. After all none of these systems are shareware, (maybe it is for those
> who don't buy it legitimatly). My advise would be if you use this service
> get
> the file translated into Step (the international standard exchange format
> PDES/STEP). With Step you have the best chance to get the most valid data
> into your own native system, then produce your own STL files from there in
> your native system. Once the file is tessellated into triangles it is
> anybodies guess what is correct and what isn't.
> I have no real problems with ACIS (.sat), Parasolid (.par), or DXF
> (.dxf)
> formats except they are all propriety and not internationally regulated or
> licensed by the ISO. Thus they can be changed at any time by the vendors to
> keep their competitors guessing Just look at the history of DXF every
> version
> is different. Most vendors wrote their DXF translators for Autocad 12 or
> earlier and havn't updated the translator since (maybe thats why the DXF
> translator is usually free). You get exactly what you pay for.
> Even with its shortcomings I believe this E-based system from Spatial
> will have a huge impact on the entire industry (talk about the right idea at
> the right time). Who knows they might be the next
> My 2 cents
> Bob Morton
> Fusion Engineering
> In a message dated 4/14/00 3:09:41 AM Central Daylight Time,
> writes:
> << Nice, nice ....
> First Spatial (usw. Autodesk) must fix thier .STL generator in order to be
> succesfull in RP. We regulary receive .STL models from Mech.Desktop wich are
> a real disaster to handle/repair, and often can't be used for running on our
> Genisys FDM.
> Anyone experienced these kind of problems too? We now usually export the
> ACIS-kernel-format and switch it to Parasolid-kernel-format (Vero
> Visi-series) If we then make a .STL export, in 9 of 10 time a correct .STL
> file is made.
> Kind regards,
> Jorn Berends
> JB Ventures BV >>
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