Platform: All Platforms Applies to: CAD Import Module, Design Module Versions: 6.2, 6.1, 6.0, 5.6

Problem Description

In CAD assemblies, small gaps or intersections between components are often expected, and some inaccuracies can even be unavoidable due to the complex nature of a design. When importing a CAD assembly file to set up a simulation, the geometric model that the simulation is based on is automatically generated by computing the Boolean union of the imported geometric objects. To resolve small gaps and intersections, the Boolean operations have a repair tolerance that you can adjust.

Errors may occur when the union between objects is computed in the presence of more complex surface intersections and when trying a larger repair tolerance for a Boolean operation in order to close gaps or collapse intersections between the objects. In these cases you may encounter errors such as "Boolean geometry operation failed." or "Failed to scale geometry. Try using a smaller repair tolerance."

How can I compute the union of objects while resolving the intersections and gaps in my imported CAD assemblies without running into these errors?


The Design Module includes 3D Boolean geometry operations that are more advanced than those in other products and that are more likely to be successful in resolving the types of intersection and gaps often seen with geometric objects imported from CAD assembly files.

If your license includes the Design Module and the Geometry representation is set to use the CAD kernel, you can select the Design Module Boolean operations check box in a 3D Geometry node’s Settings window to use the Boolean operations available with the Design Module.

The Settings window for the Geometry node.

The Settings window for the Geometry node.

After you make the above change, the Boolean operations that are already in the geometry sequence will need to be rebuilt. This also applies to the Form Union node that unites the objects in the sequence to create the final geometric model used for the physics settings and meshing. You can read more about how the final geometric model is generated here: The Usage of Form Union and Form Assembly.

With the Design Module Boolean operations, you can close small gaps and collapse intersections between objects. Go to the settings for the Form Union operation, or another Boolean operation; then set the Repair tolerance to Absolute or Relative and enter a tolerance that corresponds to the width of the gap or intersecting region. When uniting many objects with large differences in the gap widths, it can help to use several Boolean union operations, each with a suitable tolerance setting to resolve the gap between the selected objects.

To avoid having to turn on the use of the Design Module Boolean operations in every new model, open the Preferences window from the File menu, and select the preference setting Geometry3D Design Module Boolean operationsUse in new geometries.

The Preferences window.

The Preferences window with the settings for 3D Geometry Representation.