Open source / Open Standard CAD development?

Mark Arvidson sagacis at
Fri Mar 7 05:45:56 CET 2008

> The reason why I joined list is that I found the CAD files of the
> Neo1973 at the site. It is great that these files are
> available, even if they are in a proprietary data format (the ProE, not
> the STEP one), and very likely developed using a proprietary CAD
> application.

Developed with Pro/E if they are Pro/E files.

> Personally, I have a software development company, in which I have
> been developing tailored software for my clients, mostly with open
> source technologies, and sometimes with, at least well known, closed
> source techs like .NET . Therefore, it was a shockening moment when I
> during 2007 did a consultancy project for an industrial company
> producing water taps. It meant going back at least ten years in time,
> back into proprietary hell! Proprietary systems (including proprietary
> interfaces between systems) and proprietary data. CAD was done with
> proprietary software, often with more than one CAD system, resulting in
> incompatible, binary-only data.

Having come from inside that industry, I have to agree.  A very big mess.

> So my questions for the OpenMoko community are:
> * Does there exist any "usable" open source CAD systems? (Is perhaps
> Open CASCAE a viable semi-open option?)

Open CASCADE may be an option for a kernel.  I do not know much about it,
except it has been used for numerical finite analysis more than modeling.
It could probably do the work, but perhaps a bit slowly?

CAD is a very complex subject.  There are many different solutions for
mechanical design, but only 3-4 for parametric controlled modeling engines,
and they are all high-dollar proprietary software packages with extremely
rigid licenses.  To date, I know of no OSS projects to try to create a
parametric modeling engine.  The original and on-going development of the 3D
parametric modeling engines (such as ACIS or Parasolid) has taken many, many
millions of dollars, so is a major OSS undertaking, perhaps similar to the
Linux kernel.

Blender has a sort of add-on parametric plugin, but it is quite limited.
Alibre Design Xpress is free, but proprietary.

> * Is it possible to use a human readable format for CAD data? (Is
> perhaps STEP enough for development, or just a format for interchange
> between different CAD applications?)

STEP is a good, complete standard format that I believe all major packages
support well.  If I were going to create an OSS 3D modeler with human
readable format, STEP is a good way to go.

IGES is/can be a human readable format, but you lose the parametrics with
IGES.  The format was design to drive CNC machines, so is more about the
model exterior than anything else.  It's original design was based on
punch-cards, so is very heard to read by humans directly.

There are xml formats, too, but none are really very standardized.

> And the most important question:
> * Is the OpenMoko community interested in  using open source tools
> (possibly together with a human readable format) for developing
> "non-software" parts?

I think this product has primarily attracted software engineering types.  We
should get the word out to non-software people and increase the audience for
that question.

--Mark Arvidson
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