The CAD Import Module has the tools to remove them and simplify the geometry. While some features, such as fillets, grooves, threads, and holes, are required for an eventual manufacture, they may not be relevant to a particular type of simulation. Unless they are removed from the geometry before meshing, these features may lead to an overly inflated number of mesh elements, and thereby require more computational resources than necessary. Once the CAD model has been properly repaired, it may still be difficult to use in a simulation due to the complexities of the geometry and the number of small geometric features in the model. Alternatively, you can automatically locate the edges of gaps and use these edges as input to generate a new face that covers the gap and forms a solid. You can, for example, manually select faces and knit them together to form a solid using a specified tolerance to close gaps. In addition to the automatic repair that occurs on import, the CAD Import Module provides features that allow you to manually repair your CAD models after import.
Therefore, geometry repair is always performed by default during the import process to get you started with your simulations. In turn, this may lead to problems with forming valid, watertight geometric objects when generating a mesh within COMSOL Multiphysics ®. These small anomalies may result in, for example, faces that do not meet exactly at the edges or inconsistent face normals and edge directions. This may be due to numerical limitations in the computer's ability to represent complex shapes, limitations of some older CAD file format, human errors, or translation of the data between file formats. While a 3D CAD geometry is usually true to the real object it represents, small and hardly noticeable anomalies can occur throughout the geometry. This digital version contains the 3D geometry of the product together with the information needed for manufacturing it. The goal of building the CAD model is to obtain a digital representation of the real product. This information is usually available when importing CAD files saved in the native format of the software where it was created. If and when the file is reimported due to a design change, all of the selections in COMSOL Multiphysics ® will be updated and retained according to associativity rules, eliminating duplicate work. Once a file has been imported, the software reads information in the CAD files to identify the geometric entities in the file. The import functionality supports associative geometry import to retain physics and other settings on the geometry. When these changes have been made, the CAD Import Module can export them in the IGES, STEP, Parasolid ®, or ACIS ® file formats for import into other tools. Most CAD models are geometries of the objects to be manufactured, and simulation may be used to model the phenomena around this object, such as the flow of air.
In addition to fixing errors, you may want to make other changes to your geometry, such as creating a model domain around a CAD design for use in CFD, acoustics, or electromagnetics analysis. These geometries can subsequently be changed using COMSOL Multiphysics ® and the CAD Import Module. When you have installed the CAD Import Module, all CAD models and files are automatically converted to a Parasolid ® geometry using the Parasolid ® geometry engine that is included with the module.
The separate product File Import for CATIA ® V5 provides support for importing the native file format for this system. In addition, you can import the native file formats of a number of CAD systems, such as SOLIDWORKS ®, Inventor ®, PTC Creo Parametric™, NX™, and AutoCAD ®. Most CAD software supports the export of Parasolid ®, ACIS ®, STEP, and IGES file formats, which can then be readily imported into COMSOL Multiphysics ® with the CAD Import Module.