Surface Offset Difficulty

[QShan]

Hello ... I am a new user of Unigraphics V18 and I am trying to offset a non-planar surface which has been successful in other areas, but for a few surfaces I receive the error message "Highlighted Faces Failed To Offset." Could someone explain to me what is preventing the surface from being offset and how I can work around it?
As a solution to this problem I have tried to use an extrusion to offset the surface and apply a thickness. This has worked, but I haven't found a method to 'sew' two solids together. Is that possible using Unigraphics?
Thanks for your help.

 

[demco]

Qshan,
There can be a number of reasons why a surface doesnt offset correctly. Is it imported? Is it sewn, or individual patches? Are there "tiny objects" or other discrepancies in the original surface. Would it intersect itself if offset?
As far as sewing solids together, you can use unite, or you can choose the solids for the input type in "Sew"
Hope that helps, if not I would be glad to look at it for you...
-Derek

 

[karthikj]

Hi Shan,

As Derek said there can be number of reasons
I think the offset value you are giving is more,as the surface is nonlinear there will be some overlap of the offset surfaces and the option fails
Try giving a less offset value.

Thanx,
karthikeyan.J

 

[Azrael]

Use examine geometry and check the surface that gives you the problem.

Check then the minimum radius (Analysis->Mininum Radius...) of the surface so you know what´s a reasonable offset value. If there is a problem with small rads use Face analysis and check which region it is.

When you know what the problem is then we can talk about countermeasures

 

[QShan]

I ran the Examine Geometry on the whole body and it returned a message reading "self-intersecting geometry detected" and highlighted the surfaces which I have been having problems offsetting. So that tells me that these surfaces need to be fixed. This particular body can be imported into Unigraphics from a .igs or .stp file and is not a body which I created in Unigraphics. In this case, can these problems be fixed?
To give you more information about the file I'm working with, it's a model of the human torso which is imported into Unigraphics as a body with a wire frame, but I can select the individual faces (as faces) or the whole body (as a solid body). As far as I can tell, the surfaces should not intersect when offset.

Thanks again,
Shan

 

[QShan]

Me again ... I understand now that the offset value has to be less than the minimum radius which occurs on the surface. Can this be worked around though? I would like all the surfaces to be offset by the same amount and the minimum radius from all the surfaces is 0.003 inches. Preferably, I'd be able to offset the surfaces by a minimum of 0.04 inches (1mm).

Shan

 

[QShan]

Me once again ... I seem to be quickly finding solutions for myself. I have solved the offset issues, but now have trouble thickening some of the offset surfaces. So please don't take any time to try and solve my offset difficulties, they're fixed Thanks for the help!
Shan

 

[Azrael]

About the thickening problem, note that you actually are doing an indirect offset operation, so the min rad must be less then the total offset.

I would recommend you to fix/replace the original surface. If the problem is localy just cut it of and apply a new surface with through curve mesh (controlled end strings). If the problem is global then redo the surface, through curve mesh with the sorrounding surfaces and if you need more control strings extract the isoparamtric string of the original surface but check those spline before using.