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Documentation

Error: Surface Meshing Self-Intersection

Error

The meshing failed due to a self intersection in the mesh on the following entities: {entities}. The exact position is printed at the end of the Meshing Log.

What Happened?

The meshing process failed because there is one or more intersections in the model.

What Could Be the Possible Reason?

Intersection means that there are two surfaces that are going through each other. The surfaces that are intersecting are displayed in the error message as observed in Figure 1:

self intersection error message with intersecting surfaces in the model given
Figure 1: Self-intersection error message with intersecting entities given

The exact coordinates of the intersection are at the end of the Meshing log. You can access the meshing log in the simulation tree of your project.

meshing log with coordinates of intersecting surfaces.
Figure 2: Coordinates of the self intersecting entities in the meshing log

What Can I Do Now?

The only solution to this issue is to repair the CAD model in a CAD software. You can see the surfaces that are intersecting in the error message and the exact location can be found in the Meshing log. After identifying the intersections in the model, you can determine what needs to be fixed in your CAD software.

Important Information

The fix to this issue will depend on the the model and the simulation setup.

For example, the picture below is a model of a CPU heat sink that will act as an example for how two surfaces can intersect.

heat sink model
Figure 3: Heat sink model with intersections that need to be resolved

When setting up the mesh, the mesh fails to generate because two surfaces are intersecting with each other. We can see the intersecting surfaces below:

example of self intersecting surfaces
Figure 4: Self-intersecting surfaces

We can see that Surface 1 is partially intersecting with Surface 2 at the top, shown in the yellow box. This can be fixed by moving Surface 2 a little bit downwards so that it ensures that both Surface 1 and Surface 2 will not intersect each other.

For example, in Onshape you can move the faces by using the Move face command. Next, select the faces that you want to move and specify the distance. In this case, Surface 2 will move by 0.25 \(mm\) in the negative y-direction.

steps to move a face in OnShape to reduce intersections in the model
Figure 5: Steps to move a face in OnShape

After that, confirm the operation and export your model into SimScale again. Below is the mesh at the intersecting area after it is resolved.

mesh at problematic area after intersections are fixed
Figure 6: Mesh at problematic area after intersecting face is moved

Read more about how you can prepare your CAD model for SimScale here.

Important Information

If none of the above suggestions solved your problem, then please post the issue on our forum or contact us.

Last updated: October 23rd, 2020

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