To import geometry objects from a 3D CAD file, from the Home or the Geometry toolbar, click Import ().

In the Source section of the Settings window, select 3D CAD file from the Source 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.

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. Choose how to name the objects imported from STEP files from the Import body names list:

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® and Linux operating systems with Intel® 64-bit processors and on macOS.

Note 3: This format is available only on supported Windows® and Linux operating systems with Intel® 64-bit processors.

Note 5: The import of files saved with PTC Creo Parametric 12 software is available only on supported Windows® and Linux operating systems with Intel® 64-bit processors.

Note 6: Files saved with an educational version of the SOLIDWORKS® software are not supported.

When importing CAD assemblies saved in the file formats of the CATIA V5, Inventor, NX, PTC Creo Parametric, PTC Pro/ENGINEER, and SOLIDWORKS software you can display a graphical preview of the assembly components by clicking the Preview () button in the Settings window toolbar. The components are displayed in the Graphics window, where you can also select the components you want to import. See also Assembly Components to Import.

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.

When importing CAD assemblies saved in the file formats of the CATIA V5, Inventor, NX, PTC Creo Parametric, PTC Pro/ENGINEER, and SOLIDWORKS software you can display the assembly tree where you can choose the components to import from the assembly. After you have selected an assembly file under the Source section, click Load Assembly Tree to display the components of the selected assembly. You can also click the Preview () button in the Settings window toolbar to load the assembly tree and to show a preview of the components in the Graphics window.

When you click Import () under the Source section, only the components that are selected in the displayed assembly tree will be imported. Thus, to prevent importing a component you can clear its checkbox in the tree. To quickly select or clear all similar components, you can right-click a component, and from the menu choose to either Select All Instances or Clear All Instances of the component. Components can also be selected from the Graphics window when Preview () is active.

For large assemblies it may help to filter the assembly tree to display only the components that you have selected to import by selecting the Only list components to import checkbox. You can also enter any text in the Filter text box to only display the component nodes that match the filter.

The Select All () and Clear All () buttons below the assembly tree provide further shortcuts for efficiently choosing components. Use the Expand All () and Collapse All () buttons to quickly expand and collapse the displayed assembly tree. When the assembly has changed on disk, or if you select a different version of the assembly, click the Reload Assembly Tree () button to update the tree displayed in the Settings window. When reloading the assembly tree the selection of components is retained, and any new components are selected for import by default.

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

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

For the Form Solids and Knit options, the knitting merges edges that have a distance smaller than the Absolute import tolerance and deletes gaps and spikes smaller than the Absolute import tolerance. Additionally, select the Fill holes checkbox to generate new faces that can cover larger holes due to missing faces in the imported CAD file.

If a solid cannot be created while importing, you can also try the Knit to Solid operation after the import, and use a larger tolerance for the knitting. Geometry operations, see for example the Cap Faces operation, can also help with creating new faces to cover larger holes on imported geometry.

To import wireframe geometry you need to select the Curves and points checkbox. With this option, the Unite curve objects checkbox 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, this tolerance is used by some of the simplification and repair operations as detailed in this section. During the import, the repair operations are performed in the order of the corresponding settings (starting from the top) in the user interface.

If the Remove redundant edges and vertices checkbox is selected, edges and vertices that are considered redundant, such as the edges of an imprint on a face, are removed from the imported geometry.

Imported geometric objects can sometimes contain geometric and topological errors, including missing edges and vertices, and entities with invalid sense and invalid tolerance. Errors such as these can be fixed during the import by choosing one of the available options from the Fix errors list:

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.

The Delete small details checkbox is selected by default, to remove geometric details smaller than the Absolute import tolerance. Details that can be deleted include short edges, sliver faces, small faces, and spikes.

With the Heal edges checkbox selected the import tries to replace edges with a large tolerance with accurate edges calculated by intersecting the adjacent surfaces. This also improves the adjacent vertices, which become exact.

If the Minimize tolerances checkbox is selected tolerant edges and vertices on the geometry are detected, and their tolerances are reduced when possible.

Select the Check resulting objects for errors checkbox (default) 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 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 checkbox 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 checkbox 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 checkbox to make the resulting objects available only in the feature’s geometry sequence. For more information see Construction Geometry.