STEP part 42

From: Andrzejewski, Jan (
Date: Fri Feb 13 1998 - 13:58:00 EET

Dear Lex

STEP is an international standard (ISO 10303 ) STandard for the Exchange
of Product model data.

The standard covers all aspects of a product ( ie Geometry, Topology,
tolerances, materials, analysis, manufacture, test, inspection, etc ).

This is a huge task, so each aspect has been divided into parts and PART 42
only covers geometric and topological representation of the model. This is
now an International standard whilst other areas of product information
transfer are still under development.

Some of the aspects of a product have been classed into Application

AP201 Explicit Draughting ( approved International standard )
AP203 Configuration Controlled Design ( approved International
standard )

Application protocols still under development and yet to be approved as
International standards are:

Associative Draughting,
Sheet Metal Products,
Numerical Control Processes for Machined Parts,
Life Cycle Product Changes Process,
and many more.

The main problem that STEP covers is that it also specifies Conformance
Testing of the interface whilst
IGES STL DXF translators do not. This is why so many problems arise.

The next time you buy a CAD package and IGES or STL interfaces ask for and
try to get an independent certificate of conformance to the complete

STL and DXF are not International Standards, maybe VRML file format for
Faceted data should replace them but only when the steering committee for
VRML have included a verification routine that would ensure that all normals
are correctly pointing outward from the part, node to node connectivity is
tested, and other topological problems are corrected, especially facet
chordal deviation value.

I wonder If 3D Systems would allow the STL format to change to VRML ?

For more info on STEP visit

Only one reply to CAD packages with STEP or not as the case may be so far.

Jan Andrzejewski
RP Operations Manager
Pera ( Production Engineering Research Association )

For more information about the rp-ml, see

This archive was generated by hypermail 2.1.2 : Tue Jun 05 2001 - 22:44:55 EEST