IGES from CATIA

Hi,

We use CATIA V4 and also have a Solidworks 2004 station to provide
translations to our suppliers. On reading IGES files, I am noting alot of
errors on the translated files. Does anyone know any methods to clean up
files before placement in to solidworks.


Cheers

Ian

 

The way we convert is with STEP files - much better that IGES.

WT

 

Try using Rhino as a go-between. Import IGES from Catia, SaveAs IGES
for SolidWorks.

BTW, in trying to export IGES cavity and core surfaces to a mold maker
for CAM tooling we've noticed that the imported geometry can be very
squirrelly. Using Rhino seems to take out some extraneous data, leaving
pure surfaces which the CAM software (Teksoft) imports without problems.
The export options we used from SolidWorks (specifically for Teksoft)
SHOULD HAVE left pure surfaces -- and perhaps it did -- but the data in
the imported files were very problematic from multiple standpoints. The
files seemed to contain duplicate sets of data causing duplicate tool
path generation, and sometimes the "duplicate" tool paths weren't
actually duplicates (different depths, and no the cavity and core
surfaces were not offset) and sometimes they would bring the program to
a halt.

Substitute BIG for LARGE to reply directly.
'Sporky'

 

You can expect some problems with sheet metal type parts from CATIA.

CATIA's modelling kernel has a higher tolerance for error when
declaring whether entities are parallel or normal. I have had CATIA
translations of part where supposedly parallel surfaces were off by
3E-6 degrees or less. Not much, but enough to cause SW to say they are
not parallel.

The source of this error is in the CATIA file itself, not in the
translation. I did have this verified by one intrepid CATIA operator
who dug deep enough to find this.

 

CATIA

The Catia IGES translator is based on IBM IGES Format (IIF). When you
save a Catia model as an IGES file, it undergoes two translations:
Catia=>IIF=>IGES.
The IIF=>IGES step is done by the igesp program. This program has two
parameters which affect the accuracy of the model and therefore
increase the potential that SolidWorks will be able to form a solid out
of the data. You can modify these values by editing the file
igesinp.data. The 2 parameters which should be changed are:

SIGFIG COEF n
SIGFIG CORD n
where n is the number of significant digits. The default values are 8
and 6 respectively. The range of values are from 5 to 14. The
recommended values are 14 and 14.

COEF indicates the maximum number of significant digits in the IGES
file for a real number that is a coefficient of an equation.
CORD indicates the maximum number of significant digits in the IGES
file for a real number that is a coordinate.
By using the maximum values for these parameters, the size of the IGES
file can become large, but the potential that SolidWorks will be able
to form a solid out of the data is much greater.

 

I've seen similar things happen in Unigrapihcs. A sheet metal part is
unfolded, modified, refolded, and for some reason the faces are no
longer parallel or the holes are off normal by a miniscule amount.

In our position, we are not able to prompt the OEM's to fix their
files. Most users also don't understand the variable tolerance thing
enough to know how it can mess up a model.

Just be aware that it can be an issue, and the source is not just
"translation error".

 

Note that both UG & SW (and a few others) use the ParaSolid
kernel and that it's the kernel that decides what a valid solid is
(and is not).
There must be kernel tolerances ....

Sometimes I miss the old CADDS-III error "surfaces not
contiguous" (IIRC).

 

Ever hear of FormatWorks? It is designed to handle this.

Lyle

 

We had Capvidia (FormatWorks) do some repair for us. I was impressed.
For us, it is more economical to employ this type of thing on a service
basis (which Capvidia also provides).

Don't underestimate the value of a clean translation and a good repair
job. It saves a lot of time, and time = money.

Lyle:
I referred someone to you the other day. Can't remember his name,
though.