IGES and STEP export to use in LS-Dyna

[Anonymous]

Hi

I am exporting IGES and STEP files of a revolved component from Fusion 360 to use in LS-Dyna. When I import them into LS-Dyna, the skecthes that I used to create revolves are still visible and are causing issues with my mesh in LS-Dyna. I have tried deleting the sketches and canvasses in Fusion 360 before exporting but still get the same issue.

Am I doing something wrong? How can I export the solids only without the sketches?

Thanks in advance.

[jeff_strater]

Hi @Anonymous,

I'm fairly certain that what you are seeing are not sketches, because Fusion does not export sketches to IGES or STEP, only solid and surface data.  I'm not sure, exactly, from your images what you think the "sketches" are that you are seeing.  Can you annotate your images with what you are concerned about?  I'm not familiar with LS-Dyna, but how does it work with STEP data from other sources?

Jeff

[Anonymous]

Hi Jeff

Thanks for the response. Sketches might not be the correct term for what they are, but they appear to be some remnants of the profile used to create revolves. It might be important to note that only some parts of the profile remain, while others disappear. Please see the annotated images attached. I'd like to export a clean solid in IGES or STEP format.

As for LS-Dyna, I can't say how it processes IGES or STEP information but I assume that will be a fairly standard operation across software packages.

Regards

[jeff_strater]

Thanks for adding those images, @Anonymous.  It helps a lot.

What you are seeing is an artifact of the way that some surfaces are represented in Fusion's core modeler, and possibly of the way that they are represented in either STEP or in LS-Dyna.  What you are seeing is a model edge.

First, a question:  do you see this edge in the model in Fusion, or only in LS-Dyna?

In Fusion, some revolve surfaces are continuous.  So, if you revolve a shape with lines and arcs, you don't get any edges:

That's because Fusion can represent the geometry of these surface nicely.  However, if you put a spline edge in there, then you see this edge:

I don't pretend to understand the math here, but I think it has to do with the fact that you cannot represent the geometry of this face without a break in it somewhere.

I expect that other software has this same limitation.  So, if you don't see that edge in Fusion, but it does appear in LS-Dyna, then either it is STEP or LS-Dyna itself that needs this edge.  If you do see it in Fusion, then that's probably how it gets into the STEP file.

I guess none of this really helps your core issue, which is the quality of the mesh produced.  I know of no way to get rid of this edge when it is needed.  Is there any way in your mesh generation tool to  ignore this edge?

Sorry not to be of more help.

Jeff

[Anonymous]

Jeff

Thanks again for the quick response.

To answer your question, I only see the edges in LS-Dyna and not in Fusion. If there is no way to attempt to change this when exporting from Fusion, then you have answered my question, thanks.

I have previously worked with MSC FEA preprocessors (Patran, SimXpert) and I was always able to choose edges and lines to ignore. I'm sure LS-Dyna/LS-PrePost will have the same functionality, I just have to find it!

Regards