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Average Rating: -3 (2 votes) Subject: Re: IGES import with subsequent creation of a Solid model Author: Mitch Voehl Date: 2000-10-11 16:48:00The "default" and "alternate" IGES import options use two different underlying solid modeling engines for storing the imported geometry. (See section 6.2 of the Modeling and Meshing Guide.) The "alternate" method uses the traditional ANSYS (XOX) solid modeling engine, and therefore allows you to perform any of the standard ANSYS solid modeling operations after the IGES geometry has been imported.
The "default" option uses a different method of representing the geometry -- I believe that it basically approximates the surfaces (areas) of the object with a mesh of triangles. The mesh is coarse in flat regions and fine in regions of high curvature. This surface representation method facilitates the capabilities of the geometry and topological repair tools since most of these operations can be done by creating, merging, or deleting sets of adjacent triangles, rather than trying to work with the mathematics of the NURBS used by the "standard" ANSYS geometry engine.
Unfortunately, one cannot use the features of both geometry engines at the same time. If you import your geometry using the "default" method, you have access to the "new" geometry and topology repair tools, but do not have access to most of the standard geometry creation and boolean operations. If you choose to import your geometry using the "alternate" method, you have access to all of the ansys geometry creation and boolean operations (OK, so sometimes they have trouble operating on imported geometry), but do not have access to the new geometry and topology repair tools.
Unfortunately, I believe if you import your geometry using the "default" method, which stores the geometry surfaces as a mesh of triangles, that you cannot then CDWRITE out your solid model, as there is yet no way to convert the surface mesh back into the type of mathematical surfaces (NURBS, BSPLINES ?) used in the IGES specification.
Section 6.2 in the Modeling and Meshing Guide states:
ANSYS provides the following two options for importing IGES files:
DEFAULT--This option uses an enhanced geometry database and should, in almost all cases, be your choice...
ALTERNATE--This option uses the standard ANSYS geometry database, and is provided largely for backward compatibility with the previous RV52 import option.
which clearly promotes the use of the new "default" import option. Unfortunately, I have found I almost always have to manipulate the geometry after I import it, and therefore I have encountered very FEW situations where I can use the "default" option. For me, the "alternate" method is, in almost all cases, my choice.
Bottom line, if you want to create or manipulate the geometry after importing an IGES file, use the "alternate" method.
JPatterson@h... wrote:
> Karol,
> Will CDREAD and CDWRITE help you? Perhaps import your iges geometry, do a > CD WRITE, then run your APDL and then CDREAD.
> Hope it sparks an idea,
> Jim P.
> James J. Patterson > Engineering Analyst > Hendrickson Trailer Suspension Systems > 2070 Industrial Place SE > Canton, OH 44707 > Tele: 330-489-0095 > Fax: 330-489-0450 > email: jpatterson@h...
> Karol Galik > > .pitt.edu> cc: > Subject: [xansys] IGES import with subsequent creation of a Solid model > 10/11/00 > 01:07 PM
> Hi everybody,
> I got an IGES file from a company ( an implant) that has to be combined > with my > model (bones). My model is created in APDL and it will automatically offset > entity numbers if there are any entities to start with. The problem is that > ones > I transfer the IGES file with "default defeaturing" (transfer works > perfect, > Booleans work) a cannot create any additional entities. > If I transfer it with ALTERNATE I have to recreate volumes.
> Is there any way that you can create additional solid models (from new > keypoints, lines...) after the "default defeaturing"?
> Karol Galik > PhD student at ME department > University of Pittsburgh, PA > 412 624 9776 Phone > kagst34@i...
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