Imprinting Issues with Surface Models

[Anonymous]

I am transferring a part consisting of surfaces only into Simulation. When I mesh it some of the connections imprint correctly and some don't. Are there any tolerances to change that will change the result? I end up with a model that has many disconnected parts. This model consists of about 200 parts so it is quite a job to check all through it and fix it by adding beam elements at the connections.

[scudelari]

Hello!

It is interesting that you wrote this article, because I also wanted to ask the very same question.

I don't know what you are using to model the CAD object, but if you have an Inventor part which is sent to simulation, this can occur sometimes.

In my case it is even more weird because I have some mirrored parts (complete copy indeed) and sometimes it works on one side, while it doesn't on the other side.

I really wanted someone from autodesk to help us out here, and I can even sen you the Inventor file for you to check.

I discovered though these things that maybe can help you:

1- If you cut the surface in your CAD model of the object that is not having its mesh changed by the other object (the body in your example) the imprint tends to occur. It is not necessary to create another part, just cut the surface along the other object's line. Please note though that this doesn't necessarily fixes the problem. It is common for simulation to connect the element but to generate a fully srewed up mesh in the vicinity of the connection.

2- You don't need actually to create beam elements - you can modify the created mesh. You may move the vertices from the base plate in your example so that they would be on the same spot as the rib's vertices this will automatically make simulation consider it as another the same vertice - i.e. connect the mesh. The problem here is that most of the time simulation creates different number of vertices which will result in the infamous triangular elements of death.

3- I alsot found out that MESH SIZE does influence. It already happened to me that if the model is meshed as 8mm it does not connect. I made another one with a more refined mesh such as 7mm and it worked like a charm.

Anyway, I hope we can find a way to fix this. 

[Anonymous]

On the model that I had issues on the one half was a derived mirrored part from Inventor and it had problems in locations that worked fine on the original half. I also found that a smaller mesh size would improve the situation in many cases. To solve the problem I split the surfaces in Inventor along the feature lines and that worked fine (did't have to modify the mesh by hand). I also tried changing the tolerances for the imprinting but it seemed to have very little efffect upon the results.

We are definitely on the same page. My model is surfaces only. I have not tried imprinting edges or faces on solid models.

[scudelari]

Yes we indeed are on the same page. It seems that you found pretty much the same kind of workarounds as I have.

I didn't have either any success on changing the parameters for the imprint tolerances. I guess that, since the surfaces are already glued to each other on the inventor file, this exposes a bug of some sort of the meshing algorithm that should anyway connect the elements by default. Therefore changes on the parameters indeed have no effect whatsoever.

I guess you also had similar issues, but it already happened to me that although the vertices right on the connecting line are shared, the area in which the mesh spreads across the surface with bigger mesh size (suppose you would have the plate in your model with 30mm and the rib would have 30mm) is much smaller on one size than the other, causing several triangles to be created.

[scudelari]

FYI, I found out also that the problem seems to diminish (not vanish) if you open the model in Inventro fusion and from there you push it into simulation. This actually creates a DWG of the model that is then used by simulation.

check this thread.

http://forums.autodesk.com/t5/Autodesk-Simulation/Associativity-between-Inventor-and-Simulation-SURF...