To import geometry objects from a 3D CAD file, from the Home or the Geometry toolbar, click Import (). In the Import section of the Settings window, select 3D CAD file from the Geometry import list. You can also skip this step as the type of the selected file is automatically recognized by the code. Click Browse to locate the file to import, or enter the path to the file. Before clicking the Import button consider to review and configure the import settings. If you have changed some settings after importing a file, the file is automatically reimported when you click a build button.

The imported geometry objects are represented by the CAD kernel, see Working with the CAD Kernel, which is the geometric kernel used by the CAD Import Module, Design Module, and LiveLink™ products interfacing CAD packages.

Some 3D CAD formats use periodic parameterization for edges and faces. For example, a full-revolution cylindrical edge or face appears seamless in the CAD program. During import edges or faces that have a periodic parameterization are cut in two halves by inserting new vertices and edges. This is done because the mesh algorithms do not support periodic entities. You can ignore such inserted edges using an Ignore Edges feature from Virtual Operations.

Note 2: This format is available only on supported Windows® operating systems.

Note 4: Support for the NX™ file format is available only on supported Windows® and Linux operating systems.

In the Length unit list, select From CAD document to change the geometry’s length unit to the unit in the file (if the file has a length unit). Select From COMSOL to keep the geometry’s length unit and scale the objects in the file to the geometry’s unit.

Select the types of objects to import using the Solids, Surfaces, and Curves and points check boxes.

If the Surfaces check box is selected, you can choose how COMSOL imports the surfaces using the list under For surface objects:

For the Form Solids and Knit surfaces options select the Fill holes check box to generate new faces to replace missing geometry.

To import wireframe geometry you need to select the Curves and points check box. With this option, the Unite curve objects check box is selected by default to unite the imported curve objects, which speeds up the rendering of the geometry.

The Absolute import tolerance is a length measured in the geometry’s unit after the import. When importing 3D CAD files, the program merges geometric entities with a distance smaller that this tolerance.

Select the Check imported objects for errors check box to check the validity of the imported objects as the last stage of the import. Warning nodes appear with details about the detected problems, if any. Use the Zoom to Selection button next to the Entities list in a warning node to locate the problematic edges or faces. For information on geometry problems that may occur see the Check feature.

If you select the Repair imported objects check box, the software tries to repair defects and remove details smaller than the Absolute repair tolerance.

The option Simplify curves and surfaces is selected by default to simplify, within the Absolute import tolerance, the underlying curve and surface manifolds of the imported geometric entities. Importing objects with this option may improve both the performance and reliability of geometric operations on some imported geometry, for example it may help in some cases when Boolean operations on the imported objects fail. Simplification means that the manifolds are converted where possible to analytical form: linear, circular, and elliptical curves; and planar, spherical, cylindrical, conical, and toroidal surfaces. Manifolds that are converted are B-spline curves and surfaces, or certain surfaces generated by operations such as sweeping, revolving, and filleting.

If the Remove redundant edges and vertices check box is selected, edges and vertices that are considered redundant, such as the edges of an imprint on a face, are removed during synchronization.

When importing STEP files that contain multibody parts it can be useful to generate object names that include both the body and the part names retrieved from the file. Select how to name the objects imported from STEP files from the Import body names list:

If you want to make the resulting entities contribute to a cumulative selection, select a cumulative selection from the Contribute to list (the default, None, gives no contribution), or click the New button to create a new cumulative selection (see Cumulative Selections in the COMSOL Multiphysics Reference Manual).

Select the Resulting objects selection check box to create predefined selections (for all levels — objects, domains, boundaries, edges, and points — that are applicable) in subsequent nodes in the geometry sequence. To also make all or one of the types of resulting entities (domains, boundaries, edges, and points) that the objects consist of available as selections in all applicable selection lists (in physics and materials settings, for example), choose an option from the Show in physics list: All levels, Domain selection, Boundary selection, Edge selection, or Point selection. The default is Domain selection, which is suitable for use with materials and physics defined in domains. For use with a boundary condition, for example, choose Boundary selection. These selections do not appear as separate selection nodes in the model tree. Select Off to not make any selection available outside of the geometry sequence.

Select the Individual objects selections check box to create predefined selections (for all levels — objects, domains, boundaries, edges, and points — that are applicable) in subsequent nodes in the geometry sequence for each individual object in the geometry file and for each relevant entity level. To also make all or one of the types of resulting entities (domains, boundaries, edges, and points) that the objects consist of available as selections in all applicable selection lists (in physics and materials settings, for example), choose an option from the Show in physics list: All levels, Domain selection, Boundary selection, Edge selection, or Point selection. The default is Domain selection, if available, which is suitable for use with materials and physics defined in domains. For use with a boundary condition, for example, choose Boundary selection. These selections do not appear as separate selection nodes in the model tree. Select Off to not make any selection available outside of the geometry sequence.

Click a row in a table to highlight the corresponding selection on the geometry in the Graphics window. To help with identifying the color selections, these are highlighted with the colors defined in the imported CAD file. To always highlight on the geometry the color selections that you keep select from the Graphics toolbar Colors>Show Selection Colors.

The selections listed in the Object Selections section that are made available for the geometry sequence or physics setup are always available in all input selection lists, including all applicable entity selection lists. For example, the object selection of a solid object, generated for a material from the CAD file, automatically results in domain, boundary, edge, and point selections with the same name, so that you can use it to apply a boundary material, or a boundary condition. In contrast, a color assigned to a face of a solid object in the CAD file results in a boundary selection that is displayed in the Boundary Selections section, and it is available in all applicable boundary selection lists, but not, for example, in any edge selection lists.

Select the Construction geometry check box to make the resulting objects available only in the feature’s geometry sequence. For more information see Construction Geometry.