SEC: UNCLASS NEC-LIST: CAD model -> WireFrame -> NEC analysis

Michael ....
  I have spent many years developing NEC models from CAD-type files.
I must warn you that mesh structure generally used for applications like
3D Studio will not in general be appropriate for NEC modelling.
While the geometry detail may define the shape of the model, the aspect
ratio of meshes, wire lengths, angles between wires etc are generally
unacceptable to NEC. Most times I resorted to stitching up a NEC model
using the 'salient' points of the CAD model as a skeleton, and then refining
it bearing in mind the NEC modelling constraints. I have found that this is
probably best done first in AutoCAD (using Object Snap mode) to extract the
global geometry, and the in 3D Studio to create the finer structure. I use
.DXF R12 format to move between AutoCAD and 3D Studio, and have written
applications to create NEC input files from the final DXF data. This includes
the assignment of wire diameters for surface modelling using wire elements, as
well as geometry/model integrity checking. These techniques have taken a lot
of time to develop, one day I will get around to preparing an article for the
ACES journal on this sort of thing. If you need some quick guidance, please
email me, bearing in mind that I am currently on Long Service Leave, and may
not respond immediately.

Regards

Alan Nott.

-----Original Message-----
From: nec-list-bounces+alan.nott=defence.gov.au_at_robomod.net
[mailto:nec-list-bounces+alan.nott=defence.gov.au_at_robomod.net]
Sent: Thursday, 21 July 2005 20:54
To: nec-list_at_robomod.net
Subject: NEC-LIST: CAD model -> WireFrame -> NEC analysis

Hi,

I'd like to ask your advice about the best way of going from CAD models of structures (ships, planes, vehicles etc)
to wire grid models so that they can be used for NEC analysis.

We already have the structure models in OpenFlight and 3D Studio formats.

What I'd like to be able to do is take these models and create wire grids from them;
automatically would be my preference.

I'd appreciate your suggestions.

Regards,

Michael.

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